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, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.
Q: The valves on my 1975 Honda CB550 will not stay adjusted. I read somewhere that an updated cam cover is available to correct this problem. Can you offer any suggestions? — Ken Czernicki/via email
A: You don’t say whether the valve clearances open up or close down. If your valve clearances keep closing down and your adjusters are tight, then it is probable you’re suffering from valve recession. That happens when the valve seats or the valves wear down, causing the valves to sit deeper in the seat, closing up the valve clearance. You can cure it with new valves and seats. If your valve clearances are growing larger over time, I’d take a close look at the adjusters. They may not be locking up when you tighten down the locknut after adjusting them. A long shot possibility for increasing clearances would be the camshaft itself wearing down into its bearing blocks in the head, but that would only result from extremely poor oiling: I think you’d be hearing some unusual noises if that were the case. The information I have about the later covers is that they improved the retaining of the rocker shafts, which cut down on wear. On the early covers the rocker arm pins can rotate, wearing their round bearings oval. MC