Tech Corner

Technical Q and A for classic motorcycle maintenance and repair.

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2/10/2016

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, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

ABS lights

Q: I have just bought a BMW K1200RS, but I’m having a problem with the ABS lights. There are two ABS lights on the dash, and they keep flashing. I have tried to clean the sensors on the front and back wheel, but the lights keep flashing. Do you have any suggestions that I might try?  Allan/via email

A: When you start your BMW, the ABS computer initializes itself and does some internal testing. It can’t complete the final test until you move the bike. That test involves counting pulses from the sensors attached to each wheel that check to see that the wheel is still rotating when you apply the brakes. If there is no problem with the ABS system, the flashing lights should go out the first time you apply both front and rear brakes. If the warning lights stay on after that, there is a more serious problem and you’ll have to take the bike to a BMW shop that has the proper diagnostic equipment. To my knowledge, nobody has created any sort of diagnostic shortcut for the ABS on these bikes.



1/27/2016

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, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Valve issues

Q: I have a 1972 Triumph T100. While riding, an exhaust rockerbox cap came off and the adjusting pin and lock nut came off also. I probably rode it a couple of miles home with it just running on one cylinder. I replaced all four adjusting pins and lock nuts, and set the valves correctly. The bike started on the first kick and sounded good in the garage, but when I tried to take off, it has no power. I will readjust the valves, but I suspect a burned valve. What do you think? Doug/via email

A: Burned valves usually result from valve clearances being too tight, keeping the valve off its seat, where the heat gets transferred from the valve to the cylinder head. In your case, the clearances were too loose, so the valve didn’t lift at all. You didn’t say whether it was an intake or exhaust valve that the adjuster fell off of, but it shouldn’t really matter in this situation. Check your compression, and if possible do a leak-down test. That should give you more info about the condition of your engine. It’s possible that there is some carbon buildup on a valve stem or seat that is keeping it from closing fully. That would also affect power output.



1/13/2016

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, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Clutch issues

Q: I’m hoping you can help me with a couple of problems we are experiencing on our newly restored 1968 Yamaha YR2C. My son and I completely rebuilt this bike and we are experiencing a problem with the clutch. Everything within the clutch was in good shape; the plates measured up as new and the basket and bearings were good. We installed NOS (new-old-stock) springs in it, a new cable and a new release mechanism as we found out the original was cracked. The NOS replacement release mechanism came cracked as well. The cracks in it were minor compared to the original. The problem we are having is that the clutch is very heavy to operate and after a few miles it hurts your hand to use it. As mentioned, we put in new springs, but that didn’t help, and a new release mechanism. We have all the correct spacers, plates, O-rings, etc. We adjusted it per the manual, but because of the design of the clutch there is not a lot of room for the clutch plates to release, so when you pull the lever in you are really pulling hard against the end of the hub. I adjusted it to where it works, but leaves about 1/2-inch of free play at the lever and the clutch releases/engages in a space of about 1/8-inch. The design of the clutch seems backwards from what would be regarded today as normal. Obviously Yamaha didn’t continue with that design for a reason. Do you have any suggestions?

Secondly, after running the bike for a few miles and the bike is warmed up, the bike runs the carbs dry and you see a stream of bubbles coming up the fuel line from the carb to the tank. We checked for vapor lock in the tank, cleaned the carbs three times now, and installed all new jets and needle valves. The floats appear to be fine and are set at the recommended height. Do you have any idea what is wrong?

Someone suggested that this bike was known to have a problem with the carbs heating up and boiling of the fuel due to the high pipes, which form a hot box around the carb area. Not quite sure if that’s what it could be, but that doesn’t sound all that plausible to me. I could be wrong. Ian and Craig Easton/via email

A: I haven’t had the experience of working on one of those models, but from the photos you supplied I can see that even in the best situation, you don’t have much leverage to pull the clutch release. I’d start by making it as slack as possible at the handlebar, then going back to the gross adjustment screw at the clutch release. Most of the manuals call for too much clearance here, often half a turn or more. I’d try to get the rotary pulled as far clockwise as possible, then adjust the gross adjustment to take up all the slack in the clutch rod, then back off 1/8th a turn. All you really want there is to ensure there’s no constant load on the clutch rod when the clutch is transferring power from the engine to the transmission. A new spring to pull the clutch release fully clockwise might help, too, if the one you have is stretched. Other than that, I don’t know what you could do that doesn’t involve re-engineering the clutch release to give more leverage. I certainly can see why they switched to the later version of the clutch release. One last thought: In your photos, the red paint visible on the clutch components may indicate that it was a balanced assembly. If you line up all the paint marks it may be that all the components form a balanced whole.

Regarding your fuel problem, you could try wrapping either the pipes near the carbs, or the carbs themselves with some insulation to see if that improves things. If it does, you know you have a vapor lock problem. Wrapping the header pipes near the carbs with pipe wrap may be the solution.



12/30/2015

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, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Choke needed

Q: I inherited a 1988 BMW R100RT. The bike has been sitting for 15 years. I rebuilt the carburetors, and it now starts and runs, but even once the engine is warm it shuts down when you turn off the choke and won’t restart without it. Where do I go from here? Aurelio Orlandini/via email

A: Oddly enough, I just had this exact same problem presented to me at my shop on another BMW. The gas tank was rusty and flakes were finding their way into the idle jets about as fast as I could clean them. Inline fuel filters stopped the clogging. I’d pull the idle jets again and make sure they are open. I use a single wire from a discarded throttle cable (small enough to pass through without damaging the jet) stuck in the plastic straw from a carb cleaner aerosol to make sure the jets are open.



12/16/2015

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, 1503 SW 42nd St., Topeka, KS 66609, or send an email with “Keith’s Garage” as the subject.

Triumph Paint Codes

Q: I have a 1974 Triumph Trident. I am getting ready to paint the gas tank, and I was wondering if you know the paint number for the gold paint on the tank. I would like to match the paint as close to the original color as possible.Jim Tutino/via email

A: The guy to contact about Triumph paint codes would be Don Hutchinson. He has modern formulations to match the colors of the old paints that are no longer available. I got my paint for my 1964 Triumph T100 from him a few years ago. Check out his website. MC



12/2/2015

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, 1503 SW 42nd St., Topeka, KS 66609, or send an email with “Keith’s Garage” as the subject.

Setting the points

Q: I am having trouble setting the points on my 1976 Triumph T140 Bonneville. I am using the timing pointer behind the inspection plug drive side. With the pointer lined up and point side cylinder on compression stroke I set the points to just open. The book said the black-and-yellow wire is the point side cylinder. How incorrect am I? It will not start now. — Leland/Orlando, Florida

A: The pointer you are looking at is really meant to be used as a reference with a timing light. With the engine running it would indicate the fully advanced timing. If you are using it to set the timing with the engine not running, it’s important to also lock the auto-advance unit in the full advance position. To do that, you must first remove the bolt holding the advance unit in position. Next, find a washer with a center hole large enough to clear the center pivot pin of the advance camshaft. Place it on the cam, and replace the bolt that holds it all together. Rotate the cam to full advance and tighten the bolt just enough so the washer will hold the cam in the fully advanced position. Now you can move the plate to get the points to just opening, using a buzz box or lamp to indicate when they open. Final adjustment is best done with a timing light, and by setting the points for each cylinder individually. MC



11/18/2015

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, 1503 SW 42nd St., Topeka, KS 66609, or send an email with “Keith’s Garage” as the subject.

Rattling BMW

Q: I’m stumped. I have a 1999 BMW R1100R that sounds like it has a tin can full of swirling marbles as I go down the road and they are as loud as the engine. I rode the bike up into second, and then shifted into neutral and shut the engine off. The marbles swirled on. I have siliconed the front rotors to their mount plates which I was told was the problem. Still it sounded like marbles. Next I replaced the front wheel bearings, unhooked the speedometer cable and had the rear swingarm and wheel bearings checked. Marbles. Next I changed all oils, looking for metal of any kind with no traces. Short of pulling the transmission I don’t know what else to do. Any help would greatly be appreciated. — Steve Millard/Oregon

A: It seems you have eliminated the engine as the source of your noise, and probably the wheel bearings too, since you replaced them. Try your run up in gear again, then shut the engine off and coast, but this time apply the brakes one at a time, starting with the front. That will tell you if the pads are chattering against the disc. If that doesn’t do it, try coasting with the clutch pulled in while in different gears and listen for a change in the speed of the rattle. That would tell you if it is in the transmission. You could also put the bike on its centerstand and spin the wheels to see if the noise appears. Good luck! MC





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