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95’ CB750 F2n starter motor squeal /squeak

Hurricane

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My first time owning a CB750, exchanged for a 955i tiger. On collection ran fine, went to start it today , starter motor turns ,engines starts then a hideous squealing/squeaking noise momentarily .....where do I start? I’m disabled so grovelling around on the garage floor is painful.Any help hugely appreciated, I want to keep this bike and sort it out ...Thankyou in advance
 
No.

While the two designs use the same type of crap 3 roller clutch they are NOT nearly the same.

The '95 model MUST yank engine and split crankcases to get to the starter clutch assembly, it is buried in center of engine behind the crank. The earlier '79 hangs the starter clutch on the left end of crank, and it is easy to get to.

That squeak, squawk, clank, gear smashing noise is 1 of the 3 rollers slipping loose to have the other 2 skid to make noise. What that crap design does when the springs behind rollers get weak or broken or the rollers themselves get slight flats on them from the skidding.

The starter end bushing will hardly ever make noise even dry of grease because it is brass bushing on steel shaft, the squeak comes from hardened parts on BOTH sides of the friction (the super hard rollers on the hardened clutch hub). Brass is soft and will not squeak in most conditions even bone dry. It simply wears more.

The 3 roller design is crap because all 3 rollers have to lock at the exact same time and 1 being slightly behind can let the other 2 skid to make the noise, 3 rollers is not nearly enough lock up bite and why that design has so many issues. Better designs use like 6 or even 12 rollers, the more the better. On modern automatic trans that same clutch type is used with as many as 24 locking elements as any slip there will instantly tear up transmission.

To the OP................if the '95 model has been using automotive type engine oil the oil may be too slick due to the zinc replacement additives (for EPA regs) and going to a motorcycle specific oil with zinc may help greatly or even fix the issue if the parts are still good and working. Seen it before. That 3 roller clutch does not like super slick oil, it makes it harder for the rollers to lock up on the hub. For sure it works on the '79 model as I have done it myself.
 
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'...if you press the starter button while the engine is running.'

Why would somebody do that? Begging for damage. The engine is then running faster than the rollers can lock up because the starter turns slower than engine at idle speed. You are risking tearing parts up. Shouldn't happen anyway as the rollers fling out at faster rpm due to centrifugal force so trying to grab then says the springs are broken or similar.

Stop doing that.
 
'No comment.'

Just saying.............if the starter ever did manage to improperly engage, the idle speed will yank it instantly to about 5X the normal speed to break parts. That instant acceleration is a parts breaker deluxe.
 
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