Engine making a very big clunk under load - cbr600f

[c_dug]

Hi guys,

Today my CBR started making a massive clunk and momentarily loosing power when the engine was under heavy load.

It's never done it before, and it was only effected by load, not revs.

Any suggestions of the cause? CCT or clutch would be my first guesses?
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I am a bellend, I am a man of constant sorrow, I am a gummy bear, I am a rock.

[DrDonnyBrago]

[Wafer_Thin_Ham]

Did it just drop out of gear. Was it just after a shift?

CBR's can sometimes drop out of 6th if you don't shift positively enough.
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[DrDonnyBrago]

[Benson_JV]

[Pete.]

[Mrjoolz]

could be rear sprocket if chain jumping, off teeth.

:o(

[Germ]

Silly question time.....checked the chain tension,could be as simple as it being too slack and trying to slip off front or rear sprockets?

[Fizzer Thou]

Sounds like it is going to be an engine out and strip off the bottom crankcase to inspect the gearbox if the chain and sprockets are okay.
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Just talk bikes.What else is there?

Always have a 'Plan B'

[c_dug]

None of that sounds right to me.

The bike definitely didn't skip out of gear, I backed off the power when I heard the noise but when I throttled back on the power was straight there, no faffing with the gear lever needed.

The Chain and sprockets (front and back) are less than 5000 miles old and are well adjusted, it was the first thing I checked when I got to work as I recently changed the rear tyre, my first though was "oh fuck, I didn't tighten something up!"

I don't think it's the gearbox, the bike has done 43,000 miles but the gearbox is silky smooth in all gears and almost never skips out of gear.

I rode the bike back from work the other night and then in and back again today, to me the clutch feels fine. Even if it was the clutch, what would cause those symptoms? Surely the only bad thing that would happen with a warn clutch under load would be it slipping. I wasn't changing gear at the time of the noise or anything.

Just to clarify, it happened for the first time when I was overtaking a lorry down some lanes, at about 7krpm in 3rd gear. I went through a village and as I came out the other side I left the bike in first gear all the way up to the redline, it didn't do it again. So I slowed back down, put the bike in second from about 20mph and full throttled, it made the noise again, this time at a lower rpm and speed. Both of the times it made the noise the bike was well in gear. Both times the engine was under load. Both times it was in a different gear at different RPM.

To me this eliminates it being the gearbox for certain. I know it wasn't the chain and sprockets. I can't think of how the clutch could cause the described symptoms.

My CCT has been rattling for quite a while now, probably way over 10,000 miles, but it was never made so much noise that I have considered it a problem. That said, I was going to change it this Saturday anyway. If the Cam chain had skipped would the bike still be running fine? I would have thought it would cause it to run really rough or make the valves hit the pistons?

Any ideas?
____________________
I am a bellend, I am a man of constant sorrow, I am a gummy bear, I am a rock.

[Pete.]

[DrDonnyBrago]

[finpos]

I'd go with the dogs idea as well, except for the fact it's happening in different gears. If it were worn dogs I'd expect it to happen in the same gear all the time (and quickly getting worse as the case hardening gets knocked off the gears with every clunk). The feeling is exactly like a chain slipping (if you've ever ridden a knackered pushbike) and it's often mistaken as such. (Motor)bike chains have to be completely and obviously bolloxed for this to happen, though.

Which may throw you a bit of a bone in that you're not getting it into gear quite as well as you think you are, and that's often down to a partially seized gear linkage.

f.

[c_dug]

Perhaps is was in the same gear then, I'll try again on the way to work today.

I assume it's a bit of a bastard job to fix? I've never delved as deep as the gearbox before, only gone as far as top end off, or sump plate off.
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I am a bellend, I am a man of constant sorrow, I am a gummy bear, I am a rock.

[finpos]

[c_dug]

Can I not just buy this?

Don't suppose anybody near Essex wants to lend me a workshop
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I am a bellend, I am a man of constant sorrow, I am a gummy bear, I am a rock.

[finpos]

Yep, of course (although I worry about parts described with question marks ). Do a bit of research, though - don't buy it if it's a common failure because you will probably be buying more broken parts, and find out how much of the engine needs to come apart for you to fit the new bits - once again, stripping and rebuilding a high mileage 4-pot from the top is simply not worth it.

You probably only need the input shaft, btw.

f.

[Germ]

Would it be worth considering a reconditioned engine and/or gearbox?I know many engineering places will do a part-ex for your old bits and knock some cash off the recon one.

Not sure if there's any bike places that do the same though,I'm just thinking out loud here.

[Pete.]

https://www.cmsnl.com/honda-cbr600f-1993-spainkph_model2285/partslist/E__1500.html

Parts 17 and 6 are 2nd gear. 175 Euros from that place but Dave Silver might be cheaper. Either that or get them out and have at them with a dremel and a drum stone. I can't grind those the way I did Binge's but I could do a pretty good job by hand.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[c_dug]

Confirmed it was just second gear on the way to work today, avoiding using second as much as possible from now on! I assume it's safe enough just to ride around it for the time being until I can get the bits to fix it?
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I am a bellend, I am a man of constant sorrow, I am a gummy bear, I am a rock.

[Pete.]

Yes, no harm will be done if you avoid making it jump.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good