Gents,
I am hearing what (I think) is a worrying noise from my sons yz85 2021. When it gets to the sort of speed where it is just about to die (ie the lowest possible idle speed) i can hear a knocking / clanking sound. I noticed it the other week and my son says it has been making it for a little while. I think the bottom end is going out perhaps? Or is the gearbox getting worn? We just did the top end and the conrod didn't have any up and down play that I could feel.
Could it be the gearbox? If the bike if turned off and in first gear I can replicate the clanking sound spinning the rear wheel back and forth, its almost like there is slack in the gearbox being taken up. If i take the spark plug out and crank the engine with the rear wheel its all smooth until I just turn the wheel backwards and then Ill get a small clanking sound very similar to the louder one I hear when its running and just about to drop below min idle speed.
Other than that is seems to be running fine. If the bottom end were going out would I notice something at higher revs or would that mask the problem?
Bike has 110hours on it. He is a mid pack rider and not too hard on the bike. Its really well maintained, I change the oil every 5 hours and top end 30hours.
One other thing, I did find some clutch plate particles in the oil and inspected the clutch. All the plates measured up to specs but I havent replaced the clutch yet. Could those bits in the oil damaged a bearing in the gearbox?
Thanks for the help in advance!
Ok, how would "clutch slap" sound? I was scanning the internet and found someone talking about clutch slap noise and actually it sounds like it could be that to me. I test rode it and it shifts fine, makes no noises etc. Its such a slapping noise that if it was a bearing I doubt Id get 1 minute out of it.
Anyway, anyone heard clutch slap before?
Check your clutch basket, the YZ's are notorious for the rivets coming loose and it will clank at low idle.
Thank you btroxler, thats what it is! Basket is jiggling around quite a bit. Can the rivets be replaced? The basket seems to be in good condition.
I have found clutch particles in the oil last two oil changes, I guess the loose basket is putting a lot of stress on the plates.
Is it time for a complete new clutch, ie basket, plates etc?
Actually, I think the particles might be rubber bits. Im thinking the rubber bushings in the clutch are disintegrating. I think Ill just order a new basket / main gear from yamaha. Hopefully the rubber bits havent damaged anything in the gearbox!
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Update for future reference by others perhaps. The rubbers in the clutch were gone, moving back and forth maybe 5mm. There were quite a few small bits of rubber in the oil. So, if you find small bits of rubber in your YZ85 or 65 gear box oil (same basket) then thats whats going on. I got a replacement basket/main gear from yamaha it was $500 Aussie Dollars.
Bike had 110hrs on it, rider is mid pack not too rough on the bike and we used high quality gearbox oil new every 5 hours.
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