Iceman-44
CB750 Enthusiast
OK guys, got a 1980 Honda 750F Supersport with almost 29,000 miles on it. Recently drove bike down for the annual safety inspection we have here in Texas and noticed LOUD metallic tapping noise developed on return trip. Roundtrip mileage was probably less than 7 miles or so. Tapping was there regardless of engine rpm and got louder & LOUDER as I nursed it back home. Noise seemed more like a mechanical knock than the usual rattling camchain noise I’m familiar with from loose tensioners. Just having a hard time figuring out what could cause so sudden a loud tapping or knocking noise like that… Bike doesn’t get ridden much, and certainly not abused (hey, it’s a classic!), and the carbs were synched up just last year. Just weird that it was fine when last ridden and now it’s quickly developed that strange noise. Only performance issue I noticed was before leaving house was that the idle seemed unusually HIGH (2000-2500rpm). Other than that engine seemed to perform normally throughout the whole trip.
So, I’ve already started to examine bike for the usual suspects:
- Pulled left cover to see if starter clutch bolts were backing out (nope, all 3 tight)
- Pulled oil filter to see if engine was making metal (nope, oil & filter looked clean)
- Pulled oil drain plug to inspect for same (nope, no metal & oil perfectly clean)
- Pulled cam cover to inspect valve train & camchains (nope, quick scan shows nothing unusual)
- Checked to confirm correct crank-to-cam valve timing and everything lines up as it should
Getting ready to go thru all sixteen valves and check for correct clearances, but while I’m doing that just thought I’d throw this out there to the forum and see if anyone else has any recommendations on where to look next.
Seem to recall others have mentioned weird noises caused by bad starter gears or bushing wear?
Think mileage of 29K is too early to think about possibly replacing camchains due to excessive stretch? (Both tensioners were replaced with NOS parts at around 27K, but neither chain was replaced.)
Anything else to help narrow down my search? All constructive advice appreciated! THANKS!
So, I’ve already started to examine bike for the usual suspects:
- Pulled left cover to see if starter clutch bolts were backing out (nope, all 3 tight)
- Pulled oil filter to see if engine was making metal (nope, oil & filter looked clean)
- Pulled oil drain plug to inspect for same (nope, no metal & oil perfectly clean)
- Pulled cam cover to inspect valve train & camchains (nope, quick scan shows nothing unusual)
- Checked to confirm correct crank-to-cam valve timing and everything lines up as it should
Getting ready to go thru all sixteen valves and check for correct clearances, but while I’m doing that just thought I’d throw this out there to the forum and see if anyone else has any recommendations on where to look next.
Seem to recall others have mentioned weird noises caused by bad starter gears or bushing wear?
Think mileage of 29K is too early to think about possibly replacing camchains due to excessive stretch? (Both tensioners were replaced with NOS parts at around 27K, but neither chain was replaced.)
Anything else to help narrow down my search? All constructive advice appreciated! THANKS!