Tech Corner

Technical Q and A for classic motorcycle maintenance and repair.

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8/24/2016

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Rebuilding fuel taps

Q: I’m trying to re-cork some old Ewarts push-pull gas taps. How do I get the old pins out? — Jim Koenig/via email

A: The best advice is probably to replace them with something else, but if you want to keep the originals, the first thing you want to do is buy several corks so you have a chance to select some good smooth ones and also in the event you split one installing it. The brass rod that holds the cork in place is peened over into the chrome tap pull, so you have to drill through the peening. Center punch the brass and use a small bit to drill just barely into the rod. Press or punch out the rod from the pull. While you are cleaning up the brass, boil a little water and sink the corks (I know, right?) in the water to soften and swell them. Once you have the brass cleaned and the corks soft, push a new cork onto the brass rod. Take it easy pushing it over the diameter change; this is where the cork will split if it has a mind to. If you haven’t drilled off too much of the brass rod, you can re-peen the end into the chrome pull, but a little Locktite bearing fit will also help hold the two together. A very little goes a long way, and you don’t want any on the cork. Carefully fit the cork back into the tap body. I’ve been warned against greasing them, but a very small amount of silicone grease on the very edge of the cork entering the tap helps ease the two parts together. MC



8/10/2016

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

A heat-related problem

Q: My 1980 Yamaha XS850 SG runs well until it warms up, but then it starts to miss, uses more fuel, and eventually stops running. Once it cools down it will do the same again. Back in 1980, I had one of these that did the same thing, and an adviser told me that the wiring harness had some added feature to suppress radio “noise” to improve radio reception. I think that he replaced the harness and everything was OK. Is this memory possibly correct or am I losing it?! Robert O’Regan/via email

A: A few things are possible.  Generally the ignition wiring either uses suppressor wire or suppressor caps. You can tell by pulling the cap off the coil and looking at the crimped-on connector at the end. Visible wire means the spark plug cap will be the noise suppressor, while a flexible ribbon or carbon string indicates suppressor wire. Sometimes with suppressor caps, the resistor contained in the caps goes bad, but this is rare. Suppressor wires can get brittle and the inner core string breaks down. Either of these things are simple and inexpensive to replace, so that would be a good starting point. A heat-related problem that affects all the cylinders also points to a central system problem like the igniter box. Those usually are only testable with factory tools, and often tested by swapping out a known good unit. If that doesn’t help, you might consider checking the fuel/air mixture. Put a new set of plugs in and go for a spirited ride on a lightly traveled road. Take along a plug wrench. When the bike starts to miss, hit the kill switch and coast safely to the shoulder. Pull the plugs and inspect for a rich condition. I suspect rich because you say it’s worse as it warms up and the old rule of thumb is, “Worse cold, lean condition; worse hot, rich condition.” Another good check would be valve clearances. If they are set too tight, when the engine warms up it is possible the clearance disappears and the valves don’t close properly. MC



7/27/2016

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Charging troubles

Q: I have a 1966 Honda CL77 305. We all know the charging system setup wasn’t the best on these 12-volt bikes. From the factory they were weak at best. I’m trying to figure out why the stator isn’t producing 60 volts to the rectifier? I have installed two different stators and replaced the rotor as well. I also installed a new rectifier and new coils. The bike now starts with one kick, but when I turn the lights on, I start losing the DC current, as shown using my voltmeter. I have checked the red wire, the brown wire and the yellow wire going to the rectifier, as shown in the manual. I have also replaced the headlight switch, and I’ve added a new wiring harness, too. I have also installed the electronic ignition from Charlie’s Place. The new battery is simply not getting up to 14 volts when lights come on. Lights on or off, the battery is losing voltage. I could go insane over this. Bruce A. Ferguson/via email

A: We’ve been fighting a losing battle with these marginal charging bikes ever since full-time headlight use became law. It used to be that the bike would mostly be used during the day, long enough to barely get the battery to full charge. Then if you had some night riding, it would drain the battery, but hopefully not so much that you couldn’t make up the deficit the next day. I’m not sure those machines ever managed to charge a battery to 13 volts, much less 14 volts. I think your best bet is a battery tender, since you’ve replaced all the components with no improvement. MC



7/13/2016

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Cylinder problems

Q: I recently purchased a 1968 Honda CL450 with just 782 miles on it. The cylinders are out of round, apparently. I had the lower end inspected and the shop told me it was nice and tight, and the pistons are fine, also. My question is, should I bore it, which will then require a new set of piston kits, or should I sleeve it, in which case I could then leave the top end alone except for new rings? Tim/via email

A: Either of those options would work, but I think boring the cylinders and fitting oversize pistons may be easier to do and probably less expensive than resleeving. Plus you get the added benefit of a little more oomph from more CCs. What makes you think the cylinders are out of round? Is it smoking excessively? You could try the test I suggest in the first letter to confirm the diagnosis. MC



6/29/2016

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Lots of smoke

Q: I am 63 years old. I have had my own little shop under my house for about 43 years. I have fixed just about every brand in those years. I bought a 1965 T100 Triumph 500 from a friend of mine about seven years ago. When I had a little extra cash I would throw it in the bike. I finally got it running. When I fired it up the left side cylinder smoked very badly. I rebuilt the whole engine. I had the head done by E & V Engines, new valve guides and valves, new pistons and rings at 0.20 over. I cannot figure out why it is smoking only on one side. I even put another set of new rings in it and it’s still smoking. I don’t know everything, but I think I put the engine together right. I hope you can help me. Larry Petras/Ohio

A: After talking with Larry, it seems as though he’s done about all he can to eliminate the common causes of smoking. All I could suggest was that maybe the left cylinder was not concentric and that was keeping the oil scraper from cleaning off the excess oil. I suggested he back off the valve adjusters so that they wouldn’t open, and then do a leakdown test at TDC, mid-stroke, and BDC to see if there was any change in the amount of air getting past the rings. Another possibility would be a crack in the head letting oil leak down from the overhead valves. Do any of our readers have other suggestions as to what the problem may be? MC



6/15/2016

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Chain and sprocket orientation

Q: I have several Japanese 2-strokes from the late 1960s and early 1970s and have an issue that has plagued me on countless motorcycles, both new and old, over the decades. I’ve never received an explanation that would seem to justify the sheer volume of instances I have run into.

 Every time I align a chain and front and rear sprockets, I find the chain will almost never run centered over the sprockets. Now, I’ve known for over 45 years that the little factory indents/alignment marks on the swingarm are generally useless for alignment purposes, so I have used all the alignment methods I have ever seen, from name-brand alignment tools (which work great, by the way) to measuring and equalizing the distance between the swingarm pivot and the axle shaft, the string method, etc. I always check the sprockets themselves to ensure they are flat as a pancake and not tweaked. Most recently, I had a piece of steel machined to be exactly straight and laid it up against the two sprockets of my current project, finding they were misaligned by 1.65mm. I then removed 1.65mm from the countershaft sprocket spacer as there was more than adequate clearance and got those two sprockets aligned within a gnat’s behind, but to no avail. For clarification, the sprockets and chain are new and correct factory OEM parts. The result is always the same: The right inner link of the chain rides up against the right outside edge of the sprocket. Thus, the chain is slightly to the left of center. I always make sure I have the correct play in the chain measuring it multiple ways, including with the shocks removed and the countershaft, swingarm shaft and rear axle all in the same plane.

Of course I am also aware that frames and mounting points, etc., were not always perfectly in alignment from the factory 40-plus years ago and can get out of whack from living a hard life over the years. Therefore I also do my best to ensure the frame is not tweaked before I ever start on a project and rectify any noted problems I find.

Out of curiosity, I recently visited my local multi-brand dealership and I nosed around the street bikes checking the chain alignment on every brand new street bike on the showroom floor. Every single bike I looked at but one had the exact same issue. The chain was to the left of center and riding on the right inner edge. Even the used bikes I looked at had the same issue. The only bikes in the dealership that didn’t have the issue were the dirt bikes. I’ve often wondered if the issue was that the front and rear sprockets were not vertically parallel and I don’t know how to check that. But after seeing all the new bikes with the exact same issue, well, I give. Chuck Floyd/via email

A: You’ve certainly put a lot of time and thought into this, and my answer is going to be so short you may be disappointed. Once you put any load on the gearbox the shaft deflects just enough to cause the chain to pull to the outside. It’s really that simple.  MC



6/1/2016

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Stalling problem

Q: I have a restored 1972 Triumph T100R that stalls at idle. My mechanic added a Boyer electronic ignition, but left the 12-volt coils in. It has original electrics other than that, including the alternator/stator. He tuned the new Amal carbs twice and adjusted the timing twice, to no avail. Finally, he said I just have to blip the throttle when coming to stops to prevent the stall. I am wondering if this is an electrical issue or a carburetor issue. The carbs are brand new from England. They have been synchronized carefully. Could the problem be the 12-volt coils? I have heard that the Boyer prefers 6-volt coils. It starts right up every time and idles. It’s just when I run the bike normally then come to a normal stop it dies, as if it runs out of fuel or the spark to the plugs dies. This has ruined an expensive and long-term restoration. The mechanic said he has done everything he can and that it’s my riding style. I don’t believe that, as I’ve had Triumphs all my life and none have done this. Bill/Rhode Island

A: You definitely need two 6-volt coils wired in series for the Boyer ignition to work properly. Since it fires both coils at the same time (known as wasted spark ignition as one spark occurs in a cylinder that’s on its exhaust stroke) there is a need for the two coils to present the same resistive load as one 12-volt coil. Your current setup is too resistive and I think it is keeping the ignition from firing consistently at low rpm. If you’re reluctant to take it back to the mechanic, you should be able to replace those coils yourself. Just make note of the way they are currently wired and get two 6-volt coils of the same physical size to put in their place. MC





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