Technical Q and A for classic motorcycle maintenance and repair.
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.
Yamaha engine life
Q: Ten years ago I bought a 1984 Yamaha FJ1100 from the original owner — an old friend — with 25,000 miles on it. At that time the bike had been sitting for many years and it took a lot of TLC to get it back on the road. Over the years since, I’ve had to repair or replace a number of things that you would expect to fail after 32 years, but the bike has never failed to get me home from a ride. The engine is in great shape as far as I can tell and uses very little oil. When I first purchased the bike, my friend and I replaced the old clutch with one that would accept full synthetic oil, and I have run that in the bike ever since. At 40,000 miles I discovered three valves were tight and had the local Yamaha dealership adjust those. So this is my question: How long were these engines designed to run before needing major surgery? I read somewhere that the cam chain needed replacement at 50,000 miles and required the engine to be completely disassembled to replace it. Are the tight valves an indication that the heads will need to be rebuilt in the near future? Do piston rings last beyond this 50,000-mile range? It’s my understanding that the engine uses roller bearings on the crankshaft and transmission. I also read that these first year FJs were prone to having the second gear fail if the bike was abused (i.e., drag raced), but to date the transmission shifts fine. The bike currently has 42,000 adult-driven miles on it. Is it reasonable to expect another 42,000 miles on this engine, or am I just around the corner in needing a complete engine rebuild? — Tim/via email
A: Most of these questions don’t have a definite answer without some further diagnosis. For example, there is no way to know if the cam chain is worn out without checking it physically by pulling the valve cover and examining the chain. You can test for piston ring wear by doing a leak-down test or the more common check of watching for blue exhaust smoke on acceleration. Valve guide wear can be tested in a similar manner by looking for blue smoke on the overrun. Valve adjustment typically tightens up over the life of an engine with mechanical adjusters due to slow friction wear between the valve and valve seat. Several of the big Yamahas of that era had the reputation of jumping out of second gear if regularly abused, but it sounds like your bike wasn’t treated badly, so again you’re probably OK there. Overall, I’d say if you have been rigorous in your oil and filter changes and continue to inspect the used oil for unusual particles, you should just enjoy the bike and ride it for as long as it lasts, which is probably many more miles yet. MC