|New for old: New stainless steel master cylinder barrel and piston above old and tired original.
The disc brake fitted to Triumph twins starting in 1973 was generally regarded as a great improvement over the previous drum brake system. Powerful and reliable, it was good enough that Triumph used the same setup right up to the end of production in 1983. But that means even the newest disc brake-equipped Bonneville is more than 30 years old, and if you're of a certain age you'll remember the old call to action, "Never trust anyone over 30." That "wisdom" probably applies more immediately to brake hydraulics than people, and if the front disc brake on your Triumph twin has been less than useful lately, it may be time to have a look at the condition of the master cylinder.
A major issue in brake master cylinder failure is the fact that brake fluid is hygroscopic, which means it draws moisture out of the atmosphere. Over time that moisture makes the fluid gummy, and the moisture corrodes the master cylinder walls, reducing the effectiveness of the braking. Further, a great deal of heat is generated every time the brake pads grab the brake rotor, and some of that heat is transferred to the brake fluid. Brake fluid is specifically formulated to have a high boiling point because if it turns to vapor it becomes highly compressible. Moisture in the system significantly reduces brake fluid's boiling point, introducing the potential for a dramatic if not complete loss in performance when your brake system gets hot.
Fortunately, rebuilding a Triumph master cylinder is actually easier than it used to be, as most parts suppliers now provide a complete assembly that eliminates the tedious task of replacing individual parts. Being less than completely fluent in all things Triumph, we didn't appreciate this before we began our rebuild project, resulting in our swapping out our master cylinder the old fashioned way, piece by piece. Certainly, there's value in knowing how to work your way through the process step-by-step, but you can save yourself some trouble by buying the complete new master cylinder barrel assembly.
|Here's our Triumph twin master cylinder before rebuilding. It wasn't leaking fluid, but the handle was soft and pulled farther than it should.
This is not a particularly difficult project: If you can bleed your brakes, you can rebuild or replace the master cylinder. There is only one tricky adjustment to make, and we'll show you how to do it. This project should take only a couple of hours, but as always, budget plenty of time and, more importantly, take your time. You don't want to hurry a job as important as your brakes.
Just about any of the British bike parts houses will have what you need. British Cycle sells the seal kit for $22.90 and a stainless steel replacement barrel for $79.05. Or you can save yourself the hassle of a rebuild and order a complete stainless steel assembly for $134.97. The only specialized tool you will need is snap-ring pliers to remove the circlip holding the master cylinder together, and only if you're rebuilding from parts, not a full kit. As always, we suggest having a good shop manual on hand in case you find yourself wondering about some small detail.
Start by removing the brake lever. There is a 10mm nut below, and a Phillips drive screw above. Next, disconnect the brake hose at the master cylinder. Using a Phillips head screwdriver, remove the four screws holding the brake lever and master cylinder assembly to the handlebar.
Remove the small Phillips screw holding the brake switch components in the master cylinder half of the switchgear. If you didn't remove the brake lever first, this is more difficult than it needs to be.
Transfer the handle and master cylinder assembly to your workbench. The brake fluid reservoir is held tight by a single nut and washer, with an O-ring sealing it to the master cylinder barrel. Remove the reservoir.
The gray barrel is the actual master cylinder. It's screwed into the handle and locked in place with a small Allen head grubscrew. Locate the grubscrew. Using a 3/32-inch Allen wrench, remove the grubscrew.
Here's the grubscrew removed. Once the grubscrew is out, unscrew the barrel from the handle assembly. It can take a little force to release. If necessary, lock the handle in a bench vise, being careful not to damage it.
Next, with the master cylinder barrel removed from the handle assembly, remove the snap-ring retaining the piston inside the barrel.
Often, you can reuse the master cylinder barrel by cleaning and honing the bore to return it to serviceable condition. This isn't one of those times.
We knew we'd need new internal parts, and since the barrel was also beyond saving we sourced a new one made from stainless steel, which won't corrode like the original steel barrel.
Since we rebuilt instead of replaced, we had to install each part individually. Here, we've just installed the new seal on the brake piston. Use brake fluid as a lubricant when installing the seal (and when assembling the rest of the master cylinder) and work slowly and carefully to avoid damaging the seal.
Assemble the barrel, replacing old parts with new in the same order as removed starting with the check valve, followed by the spring, the cup main seal, the spring washer and piston with new plunger seal. Make sure the seals are installed so they go into the barrel open-end first. Install the new snap-ring and finally the new rubber dust boot.
Now the tricky part. Screw the barrel into the handle assembly and replace the brake lever. With the lever fully applied, slowly unscrew the handle while applying low pressure air to the outlet of the barrel. At the first sign of air leaking from the reservoir holes, stop. The piston is now in position to allow fluid to return to the reservoir when the brakes are released. If not backed out the proper amount, your brakes will apply but not release. If backed out too far, you won't have effective brakes. Loosen the handle one more turn and install the grub screw so it engages the flat in the barrel.
A close look at the master cylinder barrel (shown here partially assembled) shows the feed and return ports for the brake fluid reservoir; the feed port for pressure is the larger port to the left of the reservoir mounting stud while the return port is the smaller one to its right.
With the cylinder barrel properly installed and the grub screw tightened, replace the reservoir using the new O-ring, lubricating the O-ring first with brake fluid.
Here's the reservoir installed on our master cylinder. Make sure all parts are absolutely clean before assembling.
Assembled and ready to go, we opted to conduct a quick bench test to confirm we had good pressure before final installation, just in case we'd done something wrong.
The next to last thing to do was to install the master cylinder/handle assembly back on our Triumph, hooking up the switchgear and making sure the switches worked before installing the hydraulic brake line. Make sure to use new copper sealing washers on both sides of the brake line banjo fitting.
The last thing to do is to bleed the hydraulic system, flushing fresh brake fluid through the lines until it comes out clean and clear at the brake caliper bleeder screw. If the brake handle is soft, try tying it back overnight to purge the last bit of air out of the line.
Tool hounds will likely prefer to buy the “correct” factory tool to remove the brake caliper piston plug on Norton Commando front brake disc calipers. It works perfectly, of course, but at around $90 it’s a pricey bit of kit – especially if you’re only going to use it once or twice, or at least very occasionally.
That – and the fact we’re cheap – moved us to see if we could make our own. We did, and it couldn’t be easier. The peg spanner is, after all, nothing more than a solid bar with two pins set to locate in the caliper plug so the plug can be loosened. You can buy all the materials needed for less than $5, or if you’re like most of us, just scrounge around the shop ‘till you find a piece of scrap steel and some 1/4-inch bolts, nuts and washers.
Tools and materials used:
- 1-foot piece of 1/4-inch x 1.5-inch flat steel bar
- 2 x 1/4-inch fine-thread high-grade steel bolts, 1-inch long
- 2 x 1/4-inch fine-thread nuts
- 4 x 1/4-inch flat washers
- 1/4-inch high-speed metal drill bit
- 3/8-inch high-speed metal drill bit
- Center punch
Lay the piece of flat steel across the center of the caliper plug and mark the center of each hole as shown. They should end up roughly 13/16-inch apart. Be as accurate as possible but if it’s not exact it won’t matter, as you’ll see. We were installing a new stainless steel caliper plug, so we used it to make our marks.
Using some type of square, mark lines across the flat steel where you made your marks. Next, make perpendicular marks centered through the two lines as shown. The bar stock is 1.5-inch wide, so that means 3/4-inch in. Again, don’t worry if they’re not perfect.
Using a center punch, punch the center point of the intersecting lines. This makes it easier to drill as it gives the drill bit a point to bite so it won’t wander – especially valuable if you drill freehand.
Using a 1/4-inch drill bit, drill the point farthest out on the steel bar. We used a simple drill press with a holding fixture to keep the plate flat and make drilling easier. You can do this by hand with a hand drill, but a shop vise to hold the plate is highly suggested to keep the plate from whipping should the drill bit jam during drilling. Don’t forget to lightly oil the drill bit while drilling to keep the bit cool and lubricated.
Using a 3/8-inch drill bit, drill the second point. The larger hole will aid in the final setting of the tool, as you’ll see.
Lay all the piece out. Clean the flat bar well, using a hand file to remove any raised metal and dress the holes as necessary. We gave our bar a coat of no-rust gray primer, which we should follow up with black enamel if we’re really worried about it rusting; we’re not.
Attach one of the 1/4-inch bolts to the outer hole. Make sure to use one washer under the bolt head and one under the nut. Tighten thoroughly.
Attach the second 1/4-inch bolt and nut, again with washers as before. Center it loosely in the over-sized hole and tighten the nut finger tight only. Check to see if the two 1/4-inch bolts line up properly with your caliper plug holes. If they do, tighten the second bolt and nut securely. If they don’t, adjust the second bolt and nut as necessary to align and then tighten securely. That’s it! You’ve just made your own custom Norton Commando disc brake caliper plug peg spanner! Pretty cool, and you can use the same approach to make other “custom” tools.
|Old versus new: A 1974 Norton Commando 850 disc brake caliper stripped bare with old parts on left, new on right.
Although some people today criticize the front disc brake fitted to the Norton Commando starting in 1972 (earlier models used a twin-leading-shoe drum) for a lack of bite, they were highly regarded when new and considered superior to the drum brake setup.
It's important to remember that 40-plus years of development has resulted in performance levels in 2014 undreamed of in 1972. Former Norton employee and now Barber Museum restoration expert Brian Slark notes that when Norton introduced its disc brake, "Britain still had streets paved with cobblestones and wood blocks sprinkled with tramcar lines everywhere, and the last thing you wanted was to send a rider skidding down the road when he squeezed the front brake."
That doesn't mean the Norton disc brake was without issues, however. Similar to many bikes, disc brake model Commandos were originally equipped with chrome-plated iron pistons. The problem is that over time — and especially if moisture gets into the system or the brake fluid gets contaminated — the chrome on the iron pits and flakes, wrecking the caliper seal. Further, the steel caliper piston plug fitted to the Norton caliper tends to seize to the caliper body. The cover is screwed in tight using a "peg spanner" and the pegs — or holes — in the cover are often damaged during removal.
Stainless steel, however, won't flake, and it's extremely resistant to corrosion and pitting. That makes it a perfect material for replacement caliper pistons, something the aftermarket has long recognized. Norton didn't specify stainless steel pistons, most likely because they would have been more expensive.
For this How-To, we rebuilt the front brake caliper on a 1974 Norton Commando 850. Our caliper pistons were corroded, with the chrome surface scuffed and pitted, so along with new caliper piston seals we installed new stainless steel caliper pistons and a new stainless steel caliper piston plug. We sourced our stainless steel pistons and plug from Job Cycle, along with a rebuild kit containing new caliper seals and plug seal, and a new stainless steel bleeder screw. Total cost was $146, not including brake fluid. The brake pads had been recently replaced, so we reused ours. Budget another $30 or so if you need new pads.
|You'll need a "peg spanner" to remove the outer caliper piston plug. To learn how to make your own cheaply and easily, click here.
This is a fairly straight-forward job, easily within reach of the average weekend warrior. Although a seasoned wrench can complete the job in a few hours, we'd suggest budgeting a full morning to give yourself time for the invariable problems that come with working on old iron.
There's only one special tool required, and that's the peg spanner for removing and installing the caliper cover. The factory tool sells for around $90. As always, we suggest having a good shop manual on hand to help aid in the identification of critical parts and for proper torque specs.
To begin, remove the brake caliper. Start by unscrewing the hydraulic brake line, using a line wrench as shown to avoid rounding off the line nut. With the line free, it's a simple matter of removing the two bolts securing the caliper to the fork leg, followed by slipping the caliper off the brake rotor.
Secure the caliper by its mounting lug in a vise. Sandwich it between thin wood shims or rags if needed to avoid scarring the caliper mount. Next, remove the caliper plug. It's typically stuck fast and ours wouldn't budge at first, so we used a hand torch and gently heated the caliper body.
With the caliper heated up, the plug came out easily using a peg spanner. This was our first chance to use our homebuilt peg spanner, and it worked perfectly. Under the plug is the outer piston, which we'll remove next.
Using finger pressure or a large C-clamp or other suitable tool, push the outer piston far enough back into the caliper to expose the caliper piston seal. Using a pick, pull the seal from out of its seat, being careful not to scratch the piston bore.
At this point the piston should come out easily. The stock piston is chrome-plated iron, so we just used a magnet to "grab" it and pull it out. If the bore is really dirty, clean it with brake fluid and a green Scotch-Brite pad to get the piston to slide out easily.
The inner piston is a little harder to remove. Stuff the bore with a rag to act as a cushion. Plug the transfer port to the rear piston with your finger. Using compressed air and a blow tip, apply air pressure at the line fitting in short bursts, easing the piston out slowly so it doesn't pop out suddenly and hit your finger.
The inner piston comes out with its open end exposed. If a magnet won't pull it through, try using a pair of needle-nose pliers, spreading them out to grab the inside of the piston to pull it out from the caliper.
Once the inner piston is out, remove the inner seal with a pick. Next, remove the bleed nipple then thoroughly clean the caliper using brake parts cleaner and a green Scotch-Brite pad to remove all traces of contamination. Inspect the bore for damage, making sure it's clean with no signs of dirt or residue.
Now it's time to start putting it all back together. Before we installed the new piston seals, we soaked them in brake fluid to lubricate and condition them. After making sure the caliper is absolutely clean, install the inner seal in its seat in the caliper.
With the inner seal installed, lightly coat the inside of the bore with brake fluid, then place the new stainless steel piston into the bore, flat side first, pushing with finger pressure only to get it past the lip of the seal.
The piston will usually push home with finger pressure, but if you're worried about it going in straight secure the caliper to your bench vise, then use a large C-clamp to gently push it home. The piston need only go far enough for the brake pad slot to be fully uncovered.
With the inner piston installed, install the outer piston seal. Here you can see the inner piston in place. Once the seal is installed, lightly coat the bore with brake fluid and place the outer piston into the bore, flat side out.
Push the outer piston in with finger pressure or using the C-clamp, again making sure the brake pad slot remains fully uncovered so that the pads, when installed, are as far back as they can go.
Next, install the new seal on the new stainless steel caliper plug. It only goes on one way, but make sure it doesn’t wad up or twist in its seat so the plug will seal properly when installed.
With the plug seal installed on the plug, screw the plug home into the caliper body, using the peg spanner to ensure it's fully seated. It doesn't need to be super tight; properly seated it should be flush with the caliper body.
Next, install the new stainless steel brake bleeder nipple. Here's our caliper with all parts installed except for the brake pads. Install the pads keyed into their slots, metal side toward the pistons. They'll slip out of the bore easily until the caliper is installed; keep them in place by wedging a short piece of rubber fuel line between them.
Install the brake caliper on the fork leg (removing the rubber fuel line used to wedge the pads) and tighten it to spec, followed by the hydraulic brake line. Flush fresh brake fluid through the system. To ensure all the air is out of the system, pull the brake lever back and strap it down overnight.
The next morning, remove the strap and check the brake fluid level, topping off as necessary. If you installed new pads, it's a good idea to go out for a ride and bed them in, running up to 45mph or so several times, pulling hard on the front brake to heat up the pads. Follow this with several miles of cool down. That's it, you're ready to go!
When it comes to motorcycle repair, most of us prefer to stay away from electrical problems — and for good reason. Without the benefit of proper diagnostic tools and experience, tracing electrical shorts and other electrical equipment problems can be difficult.
But that shouldn't stop you from at least trying to suss out some electrical problems, because every now and then you get off easy, like we did recently with a friend's 1972 Honda CB750. The owner had been trying, without success, to track down the source of an intermittent running problem — typically the worst kind of problem to track because, well, it's intermittent. In this case the bike would mostly run perfectly, but then it would misfire, acting like it had one or maybe two cylinders cutting out.
A quick inspection showed fuel flow to be OK, and the ignition timing was spot on, but when we went to inspect the spark plugs the no. 1 and no. 3 spark plug caps literally fell off the plug leads after we disconnected them from the spark plugs. Looking at the plug leads, we could see that the wires inside the lead were stressed and breaking off inside the insulation. Problem found.
This is actually a fairly common problem on older bikes where the spark plug cap is screwed into the plug lead. The connection between the plug cap and the wire strands in the plug wire lead is made by a sharply threaded brass probe in the cap, screwing the two together. Years of vibration can stress the metal strands in the lead, and pulling on the leads (you should always remove plug wires by pulling on the cap) to remove the plug wires further stresses the wire, often with the kind of results we witnessed.
Many bikes have replaceable plug wires, but most Seventies Hondas use coils with permanently attached wires, meaning you have to replace the coil to replace the plug lead. Fortunately, this is a pretty easy and affordable fix.
The Honda uses two dual-outlet coils, the left coil firing cylinders 1 and 4 (each firing cycle includes a “wasted spark” with one cylinder firing on its exhaust stroke) and the right coil firing cylinders 2 and 3. The critical specs for the coils on our Honda are a 100mm center-to-center mounting pattern with a 3 ohm resistance rating when using the stock ignition points.
|Our subject bike, a mildly caféd 1972 Honda CB750, was faltering thanks to bad coil leads. Replacing the coils and their integral leads got it back on the road.
Replacing the coils is simple and well within the scope of the average weekend warrior, and barring any unforeseen issues shouldn't take more than an hour or so. Replacement coils typically sell in the $35-$40 (each) range. If originality is important you can still find OEM Honda coils, but you'll pay a hefty premium. Used coils are another option, but they're usually headed the same direction as the bad one you already have. You'll also want a set of spark plug resistor caps, which run about $2.50-$5 each. The basic process lined out here applies to just about every Seventies Honda Four built, from 350s to 750s. As ever, we suggest having a good shop manual at the ready to help aid identification of critical parts.
Similar to just about every UJM (Universal Japanese Motorcycle) ever built, the ignition coils on our CB750 Honda are mounted on the frame under the tank, out of harm's way.
To remove the coils simply unplug the color-coded electrical connections to the coil, disconnect the spark plug leads, and remove the two Phillips securing screws at the front and rear of the coil. The photo above shows why we weren't getting spark: the inner wire strands had fatigued and broken.
Here's what the inner wire strands should look like. The main photo on page 76 shows a replacement coil (at right) with a stock coil. Note the long leads on the replacement coil: Wait to trim these to length until the coils are installed on the frame.
You also want to replace the spark plug caps, which have a resistor built into them for noise suppression. Most motorcycle shops stock them, but you should make sure you have the correct type (straight or angled) before you start this project.
Our replacement coils bolted straight onto the stock brackets. Note that we underslung the coil on the bracket instead of mounting it on top like the original. We mounted it this way simply so the plug wires would be up higher under the gas tank.
The only modification required for our replacement coils was splicing in the original female bullet connectors for the ignition coil trigger wires. The original right coil trigger wire is color-coded yellow, so we cut and spliced its yellow female bullet connector to the new coil's trigger wire, which is blue.
We did the same thing for the left coil. The stock wiring harness has the left coil's trigger wire coded blue, the same as on our replacement coils: The left side ended up looking a little tidier. The splices were made using a standard crimpable butt splice, which we then sealed using heat-shrink tubing.
Here's the left or no. 1 cylinder plug lead trimmed and with its new resistor cap screwed on. We left the plug leads a little longer than stock so they can be trimmed back if ever necessary.
With all the spark plug leads trimmed and the appropriate spark plug caps installed, it's a simple matter of making sure the leads go to the correct spark plugs so your bike will run the way it's supposed to — on all four cylinders. You're done!
I have never been a fan of using tank sealers, but sometimes you don't have a choice. Recently, the tank on my 1964 Triumph T100SC started seeping at a spot weld under the right side strut securing the tank kneepad. I didn't want to repaint the tank, so the easiest fix was to epoxy coat the tank and seal the leak from the inside.
Fortunately, this is a project within most people's grasp. It's not a difficult task, but careful preparation is key, especially if you have an expensive paint job to protect. Materials needed include bolts or rubber plugs to seal the fuel tap threads, a rubber bung to seal the filler neck, plastic wrap and newspapers to protect the paint, rubber gloves to protect your hands, a container for mixing the epoxy, a mixing stick and the sealer, of course. Finally, a clean workspace with enough room to move the tank around so the coating is evenly applied is important.
When choosing a sealer, make sure it will stand up to the ethanol in modern gas. A Novolac epoxy sealer such as Caswell sealer will do that. Prepare the tank by removing anything you can unscrew from it, such as badges, filler cap, fuel taps and kneepads. If you use bolts to seal the tap holes, wrap them with Teflon tape. If you use rubber plugs, push them in firmly. You don't want any epoxy leaking out.
Most people seal tanks because of rust issues. Although Caswell says you don't have to remove the rust first, I'd rather start with a clean, rust-free surface if at all possible. I used Evapo-Rust to clean the surfaces inside the tank. Evapo-Rust is non-toxic and won't dissolve your paint, plus it does a bang-up job of removing rust. I just filled the tank and let it sit for 12 hours. I drained the Evapo-Rust back into its jug (you can reuse it until it stops being effective), then blew the tank dry with compressed air.
Once you have the tank cleaned and the fuel taps plugged, it's time to wrap the tank. First, wrap it with plastic wrap. Make several passes, completely covering the tank, including the filler neck. You're building a barrier to keep any spilled epoxy from sticking to your paint job. After the layer of plastic wrap, cover the wrap with newspaper, using masking tape to hold it on the tank. Again, cover everything; you're making an absorbent layer in case any epoxy gets through what comes next. Finally, apply another layer of plastic wrap over the newspaper to hold everything together. With a razor blade or sharp knife, make an X cut to expose the filler neck opening. Carefully pull the layers of covering back to the circumference of the cap opening. With masking tape, seal the edges of the covering to the outside of the filler neck. As a final step, after wrapping the tank I rinsed it with a cup of acetone to remove any moisture left from the Evapo-Rust and water rinse.
Make sure everything you need is within reach, because after the next step, the clock is ticking on applying the coating. You have about 15 minutes to work the epoxy before it sets up, and in that time you have to roll the tank to evenly coat the interior.
Make a filler neck cover out of several layers of plastic wrap, or use a rubber stopper big enough to seal the cap opening. If using wrap, have rubber bands to seal the wrap to the filler neck. Mix the two components of the epoxy. There's enough in the kit for two average-sized motorcycle tanks, so I only used half of each component. With the epoxy thoroughly mixed, pour it into the tank. Quickly seal up the filler neck opening and start rotating the tank. The objective is to get all the interior surfaces covered evenly, but the epoxy is thick, and it gets thicker as it cures. Roll the tank around to spread the epoxy, giving it a minute to settle with each major orientation of the tank (top, bottom, left, right).
After about 15 minutes of this the interior should have a good, even coating. Set the tank down and remove the filler neck plug. Turn the tank over and drain any leftover epoxy into a disposable cup. Once the excess is out, turn the tank right side up and remove the fuel tap bolts. Place the tank so nothing will drain out of those holes; you don't want any epoxy plugging them. Let the tank cure at room temperature for 48 hours, replace the fuel taps and any other hardware — and you should be good to go.
This is where it started. If you look closely, you can see the paint bubbling along the lower edge of the kneepad support. Fuel was leaking because of corrosion at the spot weld.
Before lining the tank we removed all the tank emblems, the fuel taps and the fuel cap. To purge the tank of any rust we filled it with Evapo-Rust, letting it sit for 12 hours followed by a thorough rinse and dry. If you still see some rust, fill it again and let it soak another 12 hours.
Plug the holes for the fuel taps. We prefer using threaded bolts with Teflon tape as the bolts will protrude beyond the threads, but tight-fitting rubber plugs will also work well.
With the fuel tap holes sealed, wrap the gas tank several times with plastic wrap, including the filler neck. Next, wrap the tank with several layers of newspaper, followed by another layer of plastic wrap to hold it all together. Note the large rubber plug for the filler neck.
Cut a hole for the filler neck and seal the plastic/paper wrap to the edge of the filler neck. Next, we rinsed the tank with acetone to remove any moisture. Doing so at this stage ensures you won't damage the paint if you spill acetone.
Next it was time to mix our two-part liner. We used an old glass mixing cup, which we threw away when we were done. Pour the mix into the tank and seal the filler neck with a rubber plug or tape, then start rolling the tank.
Spread the liner mix by rotating the tank for about 15 minutes, letting it sit for a minute or so on each major surface (top, bottom, left and right sides). Once you're comfortable the tank's thoroughly coated, remove the plug from the filler neck and drain excess liner out the neck and into a disposable container.
After draining the excess liner, carefully and thoroughly clean the top of the fuel filler neck of any epoxy that might have settled on it so the gas cap will seat and properly seal.
Position the tank so no liner can drip from the fuel tap holes and remove the wrap, followed by the fuel tap plugs. Leave the tank in this position for 48 hours to let the epoxy liner thoroughly cure. Once cured, reinstall the fuel taps and any tank hardware. You're done!
In the March/April 2013 issue, we showed you how to install relay-switched horns on a 1980 Honda GL1100. While we replaced the GL's original horns, the thrust of that How-To was installing a relay to operate the horns. That's because your horns will work better powered and switched by a relay rather than a horn button, which can wear and get dirty, impeding voltage.
Much as your horns can perform poorly powered through an old switch, so can your headlamp, but with potentially more dire results. That's because headlamp output drops exponentially with voltage drop. According to headlightservices.com, a 9006 halogen headlamp bulb rated at 1000 lumens at 12.8 volts drops to 510 lumens at 10.5 volts, a 49 percent drop in output from an 18 percent drop in voltage!
On an older bike operating without a headlamp relay voltage drop to the headlamp is typical, the result of a worn and dirty headlamp switch and sometimes made worse by a long wiring circuit. Fortunately, you can ensure proper headlamp voltage by installing a relay.
There are different relay kits on the market to accomplish this. One of the simplest we've seen is the Matchbox Dual Headlamp Relay from Cu Layer ($45.95; culayer.com
), which has dual relay function providing high/low beam circuit control from a single unit. It's also small (about the size of a box of matches, hence the name), so it fits easily into just about any headlamp shell.
We installed our Matchbox Relay in a 1974 Yamaha TX500, which, like most bikes of its era, uses a simple handlebar-mounted powered switch to toggle between low and high beam. Installation was easy, even accounting for removing the gas tank so we could run the necessary dedicated power circuit to the 12-volt relay. The only wires we cut were the wires from the headlamp socket so we could run jumper wires to the relay. In the case of our Yamaha, which uses a standard three-prong headlamp socket, we could have kept the original socket unmolested by substituting an off-the-shelf universal replacement, splicing it into the circuit instead. The Matchbox Relay is not waterproof, so it's important to mount it where it will stay dry, either in the headlamp shell or tucked up high under the gas tank.
The simplicity of this install makes it something of a no-brainer as modifications to the original circuit are minimal: you simply piggyback onto it, using the original switch on the handlebar to signal the relay, which then switches the headlamp. The relay always has full voltage (in our case 12 volts), and any voltage drop at the handlebar switch becomes inconsequential, as 6 volts is enough to activate and hold most 12-volt relays. The Matchbox Relay is also available for 6-volt systems.
|This is all it takes: a relay, a wiring diagram — just in case — and a handful of bullet connectors.
It only took us about an hour to install our Matchbox Relay, and the improvement in headlamp output was immediately apparent. Before installing the relay, we were only getting 11.31 volts to the headlamp from a battery showing 12.72 volts, an 11 percent drop in voltage. With the relay installed, we had 12.48 volts, or just less than a 2 percent drop.
Installing a relay pretty much guarantees brighter lights, making you that much safer on the road. As usual, we suggest having a good workshop manual at hand. Wiring can be a bit like spaghetti — it's everywhere — and it's handy having a wiring diagram for reference.
Start by removing the headlamp assembly. On our Yamaha that meant simply removing two screws positioned at roughly 8 and 4 o'clock on the shell, then lifting the headlamp up and out.
Before we installed the relay we measured voltage at the headlamp socket. With 12.72 volts at the battery we were getting 11.31 volts at the headlamp, an 11 percent drop.
We had to wire in two jumper wires from the stock wiring to the relay, one from the low beam circuit and a second from the high beam.
The only wire we had to cut was the high beam from the lamp socket so we could connect the socket to the relay. The wire from the stock loom now runs to the relay input to switch the beam.
It's hard to get lost with this particular install as the relay has a basic schematic printed on the back. All we're doing is rerouting the high/low beam circuits to the relay, then connecting the relay to the headlamp.
The relay requires a dedicated 12-volt power source. We ran 14-gauge wire (red for positive, black for negative) from the headlamp shell to the battery, securing it as needed.
To protect the relay circuit we spliced in a blade-type 15-amp fuse close to the battery, which we first disconnected before final wiring. We placed it here simply for convenience.
We secured the relay to the inside of the headlamp shell with self-adhesive hook-and-loop material, placing it high to ensure water won't collect should the shell get wet inside.
With the relay fully wired in a final check of output to the headlamp socket showed voltage had climbed to 12.48 volts from 11.31. Simple and effective, this is an excellent upgrade for just about any vintage ride.
When the new-for-1975 Honda GL1000 was introduced, it was the world's first mass production water-cooled, shaft-driven flat-four motorcycle. Evolutionary and revolutionary, it employed proven practices in an entirely new package.
One of those practices was water cooling, up to then seen on only a few motorcycles, including the classic 2-stroke Scott and Suzuki's GT750 2-stroke triple. The Honda GL1000 was a hit, with some 100,000 sold in the U.S. during the model's 1975-1979 production run.
Honda followed the GL1000 with the 1980-1983 GL1100. Slightly larger and with more creature comforts, the GL1100 was mechanically very similar to the GL1000 and continued the GL's reputation for solid engineering and bulletproof reliability.
Yet as reliable as those bikes were — and still are — the youngest Honda GL1100 is now pushing 34 years of age and the oldest GL1000 39. Time flies when you're on two wheels. And as these were bikes made for touring, a typical GL1000 or 1100 today can easily be approaching — or exceeding — 100,000 miles. These bikes amass high miles with ease, but like any bike they have critical points of maintenance that are often overlooked.
On the GL, one of those points is the water pump. An obvious sign that replacement is nigh is a slight coolant leak from the "weep" hole in the front engine cover, directly below the water pump. When the water pump's seals start to fail, coolant will pass into the front cover and out this hole.
Another indication of imminent failure is a grinding mechanical noise in the front cover that changes with engine speed. Noises here can be from bad timing belt idlers or from a failed or failing water pump bearing, which is usually accompanied by coolant leaking out the weep hole. Either way, it's time to change the pump before it fails completely, possibly causing coolant to mix with the oil.
The water pump is housed in the front engine cover, which contains the transmission shift linkage and also serves as the mount for the engine oil filter. Oil is constantly circulating inside the cover and through channels feeding the oil filter. Additionally, the water pump is driven by the oil pump; if the water pump fails catastrophically, it can lead to a world of hurt.
Although not technically complicated, replacing a GL's water pump requires patience, so plan accordingly. More experienced wrenches can probably complete the job in under three hours, but if you're an average weekend warrior, make it easy on yourself and spread it out over two days. That'll give you plenty of time for cleanup and unanticipated issues.
|Telltale "weep" hole under the bottom of the GL's front cover. The stain is from leaking coolant.
Whether a Honda GL1000 or an 1100, the process is basically the same. Some models have frame-to-engine clearance issues, requiring removing/installing bolts with the front cover. We drained the oil hot, then let the engine cool down before draining the coolant. We used a factory Honda replacement water pump and aftermarket seals. The pump was the correct updated unit, but the aftermarket seals bit us in the you-know-what. How? The replacement 56mm water pump O-ring in our kit was defective, resulting in a leak. We had to do it all over again, something we know you don't want to experience.
As always, a good shop manual is essential for necessary torque specs and to help guide you through the process.
To start, put your GL up on its centerstand and place a drain pan under the front cover. Remove the oil drain plug followed by the oil filter assembly and drain the oil completely.
Remove the radiator guard, then the upper and lower radiator mounting nuts and bolts, and attaching plates. The hoses and upper stud bolts will hold the radiator for now.
Next, remove the coolant drain plug under the front coolant inlet and drain the coolant. Loosen the lower hose at the radiator, then remove the two bolts securing the coolant inlet and remove the lower hose complete with the inlet cover.
As the coolant drains, remove the GL's "gas tank" assembly. With the tank off, remove the two hoses at the plastic coolant overflow tank and remove the tank. The tank is held by a bolt at the bottom, with a stamped steel strap bolted to the frame securing it at the top.
Now we're getting somewhere. Remove the two remaining bolts securing the intermediate water pump cover and you'll see the water pump.
It's a good idea to map out the front cover bolts, as they vary in length. We used our new gasket to make a pattern on a piece of cardboard, transferring the bolts as appropriate.
Disconnect the cooling fan electrical connector, located just above the cooling fan. Loosen the upper radiator hose at its connection to the engine and gently ease it off the engine while holding the radiator. The radiator should now lift out of the way completely.
With the radiator removed you can see the rest of the bolts you need to remove to release the front cover with the water pump. Loosen each bolt slightly, then remove them and transfer them to your cardboard bolt map.
Next, gently work the front cover off the engine. It can require a little persuasion, but it should come off fairly easily. We were lucky, as the gasket stayed with the cover; it's much easier to remove the old gasket from the cover than from the engine case.
Next, flip the cover over and remove the three bolts on the inside securing the water pump to the front cover. We've already removed two here, with the third just being removed.
Support the cover on blocks of wood. Using a suitable socket, knock the water pump out of the front cover. It should come out fairly easily.
Here's our old water pump (on the left) next to the latest Honda replacement pump. The original used a molded Bakelite-type impeller where the replacement has a stamped steel impeller.
Here's our gasket and seal set. It might look a little intimidating because of all the O-ring seals, but their location becomes pretty self-evident as you remove the old ones and prep the area for reassembly. Clean all parts thoroughly to prepare for reassembly.
The kit includes a new water pump to oil pump shaft seal. Note also the large O-ring and the smaller O-ring to the left. Pry the seal out with a screwdriver and remove the O-rings.
Clean the seal area and the O-ring seats. Install the seal using a suitably sized socket. It presses in quite easily. Locate and remove the other O-rings. Clean their seats and install the O-rings after giving them a light coating of silicone grease.
After ensuring the front cover is clean, dress the two water pump O-rings with silicone grease and install them on the water pump. Press the water pump into the cover by hand. It should go in fairly easily, and its offset design means it will only go on one way.
Bolt the water pump to the cover using new aluminum washers supplied in the gasket kit. Make sure all O-rings are in place and the engine and cover sealing surfaces are clean. Install the new cover gasket dry, without any sealer, on the engine. The locating dowels will hold the gasket in place.
Before you re-install the front cover, make sure the water pump shaft and the oil pump shaft are clocked the same. The oil pump shaft has a slotted protrusion that keys into the water pump shaft. Clock them both at 9 and 3 o'clock. Next, install the cover in place, locating it on the dowels.
Loosely bolt the front cover in place, followed by the intermediate water pump cover with a new gasket, again without any sealer. Tighten the cover bolts evenly. Factory torque is 9ft/lb. Install the drain plugs with new sealing washers and the oil filter assembly using a new filter.
We'd read that a NAPA 7733 radiator hose could be cut in two and used to replace both upper and lower hoses. As you can see, they line up pretty well. Purchased from Honda, the stock hoses list for $76.63; the single NAPA hose cost us $16.49, plus tax.
After cutting our NAPA hose in two, the new upper hose (the left of the right pair of hoses) looks almost identical to the original. The lower hose is straighter than original (the left of the left pair of hoses) but hot coolant will let it relax once it's installed.
Next, it's time to prepare the radiator for re-installation. We found it easiest to attach the upper hose to the radiator before installing. Your bike may or may not have the original radiator clamp protector as shown here to keep the clamp from chafing on wiring.
Hang the radiator on the fixed upper locating bolts. Attach the upper locating plate and nuts loosely to secure the radiator in place.
With the radiator loosely attached, slip the upper radiator hose onto the outlet at the engine and tighten the clamp. Check the position of the upper clamp; we had to adjust ours. Connect the cooling fan connector.
Attach the lower radiator locating plate and bolts. Tighten the upper locating nuts. Loosely attach the lower hose to the radiator and the lower inlet. Put a new O-ring greased with silicone on the inlet base and bolt the inlet in place. Tighten the radiator clamps, then reinstall the radiator guard.
Install the coolant overflow tank. Double-check mountings and hose clamps, then fill the cooling system with a 50/50 mix of distilled water and silicate-free antifreeze. Give the system time to "burp" then top off the radiator.
Refill the crankcase with fresh oil, then start the engine and run it for a few minutes. You'll probably have to top off the coolant a few times before it's full. Run the engine to full operating temperature and look for leaks and any sings of overheating. Fill the overflow tank to the marked line and that's it!