Motorcycle Classics Blogs >

Tech Corner
Technical Q and A for classic motorcycle maintenance and repair.


Suzuki TC185 Timing

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.

Q: Greetings. I acquired a non-running Suzuki TC185. I tested it for compression and it showed more than 100psi. Next I replaced the points, condenser and the coil. Before it had no spark, but all the electrics worked great. Now I have strong spark, but the bike still won’t fire. I believe the timing must be off since the screws were all loose on the plate. Can I set the timing without the engine running, or at least get close so I can get it started and play with it? I would appreciate your advice.
— Steve Vancamp/via email

A: All I can find is info on a TS185 single. It says to use a buzz box or light on the black wire to the coil. Turn the ignition on and rotate the flywheel counterclockwise until the tester indicates the points are open. At that point look at the dimple on the case at about the 11 o’clock mark and see if it coincides with a line on the flywheel. If it doesn’t, you have to remove the flywheel to move the magneto plate, loosely reinstall the flywheel and test again. Repeat until correct.

1967 BSA Spitfire Flat Battery

 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.

Q: I have a 1967 BSA Spitfire. I’m continually having problems with the battery, as using the headlight seems to be flattening the battery. What upgrades do you advise?
James Wootton/via email

A: Since daylight headlights were not required when your bike was built, the charging system was set up to keep the battery well charged with the headlight off, and slightly discharging with it on, on the assumption that most of the running would be in daylight hours and so the battery would be maintained. First of course is to make sure your battery is in good condition, and if it isn’t, replace it with a good battery. I prefer AGM batteries for my classics for their superior energy density and long life. An added bonus is you never have to worry about acid leaks damaging paint or chrome. There were two different alternators used, a two-wire and a three-wire. If you have the three-wire alternator, make sure the green/black and green/yellow wires are joined together to the green/yellow wire in the wire loom. That provides the maximum power output from the alternator. As usual, there are a number of ways to avoid flattening the battery and/or getting more power out of the alternator. You could switch the headlight and taillight bulbs from incandescent bulbs to LEDs, being careful to source LEDs that are made for positive ground. That’s probably the fastest and least expensive method, but may not completely fix the problem. Slightly more expensive would be replacing the two-part rectifier and zener diode regulator with a one-piece combination rectifier/regulator, which may provide a more efficient conversion of AC to DC, but again may not completely fix the problem. The most expensive method would definitely fix the problem, and would consist of replacing the rotor with a new and presumably more magnetic rotor, the single phase stator with a three-phase stator, and the regulator/rectifier with a three-phase version. That would certainly provide enough output to keep the battery charged and the lights on.

1981 Suzuki GS1000G Gauge Additions

 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.

Q: Keith, I enjoy reading your responses to questions, and I would like your advice on my 1981 Suzuki GS1000G. I am now retired and hope to make some trips in the Midwest with this bike. I have always been a believer in engine monitoring gauges in my vehicles. From time to time I see an oil pressure gauge added and some older Brit bikes have an ammeter. Gauges on my radar are oil pressure, oil temperature, voltmeter and maybe a cylinder temperature gauge. What is your advice on adding gauges to this bike?
Dwight Plucker/via email

A: For the most part, the more information you have the better, but there’s a reason these gauges are often derided as “worry” gauges. Your bike has made it to 2019 from 1981 without any accessory gauges fitted. Of the ones you list, I think the oil pressure gauge would be the most informative, and likely to save you major dollars in the event of oil pressure loss. The others would be fun to look at, but would just be more things to take your eyes off the road. Of the bikes in my collection, I only have an added oil pressure gauge on my Trident, because on it the oil pressure warning light is more like an indication that engine damage has already occurred.

1979 Triumph T140E Troubles

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.

Q: I have a 1979 Triumph T140E with 17,000 miles on it. I’m the second owner and it has been well maintained. However, I’ve been stumped by an issue lately that I hope you can help me with. The bike starts very easily and idles well. When I’m accelerating, say from a stop sign, it has a stutter and occasional mild backfire at approximately 2,000rpm. It clears up at 2,500-3,000rpm and runs strongly after that to higher revs. If I roll on the throttle slowly, it does not do it. If I accelerate briskly, it will. It started doing this one day when I noticed it stuttered once. Then a few days later it did it a few more times. Then later it did it all the time, as it is now. I’ve adjusted the valves, checked all the electrical connections, cleaned out the carbs half a dozen times, all to no avail. The battery is in good condition. One day I put a new plug into the right side cylinder, and the problem went away. But 10 miles later, it came back. When I inspect the right spark plug, it is more black and sooty than the left plug. Could I have a bad or weak coil? Is there a way to measure/check the coil to see if that is the issue? Any other things I should be checking? What can I do to find and cure this situation?
Steve Sullivan/via email

A: You can check the coil for primary and secondary resistance, but you may find it passes those tests only to keep acting up. That year had the Lucas Rita wasted spark electronic ignition, so the coils are run in series. Usually if one coil fails the whole ignition circuit quits working, although if one coil was shorting out instead of opening up, the other coil would continue to fire. Since it is wasted spark, and since you found that it improved with a new spark plug on the right side, it would be informative to swap spark leads from left to right coils and see if the problem moves to the other cylinder. The service manual for that year says to set everything by the left plug, and notes that the right plug will almost always be darker.

BSA M50MX Under Water

 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.

Under water

Q: I have a 1972 BSA B50MX that was under water for 72 hours or more back in 1997 due to a river flood in Dallas, Texas. The owner couldn’t turn it over after several attempts, and at that point he just quit and sold it to me. He impressed upon me the main bearings were steel and must be replaced. It’s been on the back burner ever since. I’m hesitant to turn it over to someone without knowing what it really needs. I believe I could do it, but I also know older bikes have tricks you don’t get in manuals. Do you have any suggestions? 

Jerry Weber/Florida

A: Jerry, this sounds like something that won’t respond to my usual mix of solvents to free up an engine. You will probably have to use Evapo-Rust or Metal Rescue or something similar and allow them time to work their magic. Remove the spark plug and fill the cylinder and also fill the sump via the rocker boxes and pushrod tubes. Give it a week or so and drain the sump so as to not hydro lock the engine when trying to turn it over. Pull off the primary cover and using a proper sized socket on the crank nut, gently try turning the engine over. If it moves at all reverse the ratchet and go back the other way. Carefully working back and forth you should be able to free the engine enough to get things rotating. Don’t go too far though. Once you have the piston and crank bearings loose, you’ll have to do a complete overhaul as those main bearings will be useless from corrosion, as will many other moving, rotating and sliding parts.

1974 Honda CB550 Petcock Questions

 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.

Petcock questions

Q: I have converted a half-dozen 1974 to 1976 Honda CB550s to café racers. The first two went to my two sons. My current problem revolves around the petcock on a 1974 tank. This particular unit is specific to the 1974 model. Later years used a 20mm bung and a completely different style petcock. The original had a rusted out bowl, so I purchased a repro from a reputable supplier. I always test new components before installing them. On the bench I have the tank full of fuel, petcock installed and a catch basin underneath. When the unit is put in reserve or on, the fuel flows out of one port only. I am sure you are familiar with the 4-carb setup on the little CB’s, each port supplies two carbs in the set. If I put my finger over the flowing port, the other starts to dispense fuel. I can move my finger back and it starts to flow out of the open port. The engine will not run properly with this problem. Two carbs in the set are always short on fuel.

I had this problem on another 1974 tank on a build several years back. It was solved by cutting out the petcock mount and attaching a bung from a 1975 tank. Then I installed a 1975 petcock. I would like to keep this bike as stock as possible, so I am taking some time to try to solve this problem. The supplier is sending me an OEM part to replace the repro, and I am hoping for a good result — two ports flowing simultaneously. Based on the problems encountered on the last 1974 that I worked on, I fear that the OEM unit will not help. Is it possible that the system is designed to fill two carbs and then switch to filling the other two? I can’t see how this would work, particularly at any throttle opening above half? Any thoughts you have would be greatly appreciated. I always look forward to your column.

Gerald Delaney/via email

A: I think that once the carburetor bowls are full and all the air bubbles work their way back up to the petcock and tank, the lines from the petcock will act more like a siphon and hydraulic pull will cause them to both flow evenly. You could test this by hooking the petcock up to the carburetors and remove the bowls from one carburetor on each feed line. Holding the floats up on the open carburetors should allow the other two to fill and stop the flow. You could then release the open bowl floats and see if they drain an equal amount over time into separate containers.

 







The sound and the fury: celebrate the machines that changed the world!

Motorcycle Classics JulAug 16Motorcycle Classics is America's premier magazine for collectors and enthusiasts, dreamers and restorers, newcomers and life long motorheads who love the sound and the beauty of classic bikes. Every issue  delivers exciting and evocative articles and photographs of the most brilliant, unusual and popular motorcycles ever made!

Save Even More Money with our RALLY-RATE plan!

Pay now with a credit card and take advantage of our RALLY-RATE automatic renewal savings plan. You save an additional $5.00 and get 6 issues of Motorcycle Classics for only $29.95 (USA only).

Or, Bill Me Later and I'll pay just $34.95 for a one year subscription!




Facebook Pinterest Instagram YouTube Twitter

Free Product Information Classifieds

click me