Motorcycle Repair: deceleration rattle, oil starvation, clutch basket

Question

HWY 129 last Fall   Jan,  I have a 1979 CBX that has 10,000 original miles on it and a few later model upgrades including the newer clutch basket and new alternator plates.  I have owned this bike for 18yrs and have personally rebuilt and synced the carbs twice.  It takes a while, but when done right, my bike runs and idles super quiet.  My question though, is within the last 1,000 miles or so, I have noticed a metallic rattling noise only when the bike is fully warmed up and only when decelerating at lower RPM's.  I do not believe it is the Alternator plates that are notorious for this type of noise and I check mine frequently and have even refaced them.  This noise almost reminds me of a poorly adjusted timing chain.  I've owned two 400F supersports that were very load cam chain rattlers.  I know this engine is much different, but do you know of any Cam chain tensioner issues on the CBX, specifically any failure of the tensioner to deliver the proper tension when the two bolts (front and rear) are loosened on a warmed engine and Idled, then tightened back again as the shop manual advises to do?  If not, do you have any advice as to another cause for the light, metallic rattle on a 10,000 mile motor when not under load and engine is doing all the braking during deceleration?

Thanks for any assistance,

Mike

Answer
It sounds like perhaps the usual case of a little oil starvation in the top end after running at elevated RPM's?  I would NOT recommend the tensioning procedure you mention, I always take the cover off the top and watch the tensioner after loosening to ensure that it tightens the chain. Wiggling the crank has a huge effect on where the tensioner ends up...

Good luck,  Jan