I have had my CBR100Fl from new (1991). It is in imaculate conditions and is my pride and joy! It has done 57000 miles.

It runs like a dream but there is one ****ling problem for which I would be so grateful for advice.

When the engine is cold and as you let the clutch out in first gear there is a rattle. It sounds like a few small stones in a tin can. Once the engine is warm it does not happen. You can't feel anything and it does not affect the ride or clutch action at all. It has had a new clutch but this did not cure it. It does not seem to be getting any worse. Its probably placebo but I get the feeling its a bit better after a carb balance?

I have tried to get a diagnosis from many many mechanics without luck. I just get "probably the gearbox, don't worry about it". But I do worry! It's the only fault in an otherwise perfect and totally original machine!!

I am very reluctant to let some one strip the engine down without first knowing exactly what needs replacing beforehand because it's so smooth and sweet at the moment especially if its just, say, something to do with the clutch mechanism?

I would be grateful for any ideas from forum members. Maybe some one had also had this issue and found the cause.

Thanks
John A

 

Welcome to the CBR Forum John,

Does the noise occur while warming up the bike out of gear?

My first instinct says timing chain.

Cheers, SB

 

^ +1 Classic CCT. Surprisingly got 57k out of it.

Welcome to the forum.

 

Hi and thanks for the reply.

No, the noise does not occur when warming up out of gear at all. Out of gear the engine runs sweet as a nut at any revs. It's only when you engage 1st or 2nd and let out the clutch at low revs. Once I am over about 1800 revs there is no rattle either. In other words if I rev up the engine to 2000rpm before letting out the clutch I do not get the rattle.

I fairly sure it's not the timing chain/tensioner as I had a new ones last year and it made no difference? Also the sound seems to be coming from the clutch or gearbox area.

Best regards

John A

 

My '90 has done that since new. You are right, it isn't the CCT. Mine tends to do it more when cold, as well. The bike has 67,000 miles on it now, and the noise seems to be of no consequence. Beats me what it is, though.

 

If its not the CCT, it is a bit confusing.

I wonder if its fuel or timing related. Pinning like a bat at a rock concert.

What would happen if you run some injector cleaner through it and run high octane?

If it were me, I'd do that just to see if things change at all.

 

A little slop in the clutch basket would be my guess. It will chatter as you engage under light load, however if you are more aggressive(higher revs/quicker engagement) you don't hear it because the power applied to the clutch is more positive with higher revs. Then if the lever is released more quickly the plates settle into position against each other and their respective keyways in the basket/drum.
If you are hearing it after the clutch is fully engaged, it is more likely in the transmission.

 

After that sort of mileage I'd be inclined to replace the clutch plates anyway ( very easy DIY job ) and see what it does. If after that its still doing it then like cb2cbr says it could be inside the transmission which will require pulling it apart and checking it out. I hope it's just a worn clutch.

 

Thanks everyone.

It's had a new clutch and basket so I assume it's not that? Mind you. I've a feeling that the clutch action is not as smooth and progressive as it once was?

As ofreen says I have been told it's of no consequence but I would really like it cured.

I guess the only way is, as has been said, to strip the engine down. It's not something I could do myself and I do not know how to go about finding a mechanic with sufficient skills and who I can trust to take care to put it back together again perfectly and in the condition the engine is in now? If I knew what it was that would at least restrict the amount of disassembly that was necessary. I am also scared that once in bits it might not be possible to get hold of the required part?

How big a job is it to replace the gearbox and are new gearboxes still available?

Cheers
John A

 

It only happens when the engine is cold and at low rpms. Sounds to me like a fuel issue, not a problem. Try leaving the choke/enrichener on a little longer. Not full on, just partially. It might be a little lean and your pinging. Try a little Lucas carb/injector cleaner. I dose my tank with 1 oz. every fillup. Lucas and Seafoam are the only cleaners that I have noticed any improvement with use.