Occasional clunk noise when letting out clutch in 1st gear?

ggr · L Plate Warrior Joined: 01 Jul 2018 Karma :

Hey all,

What seems to be the clutch/gearbox on my XT600 recently started making the occasional clunk sound when I'm in first gear with the clutch lever pulled in and start letting it out. It isn't accompanied by any judderiness but the noise is a bit disconcerting.

Any ideas on what could be the cause of this? The bike had some stuff done to it a day before I started noticing it happening:

- changed the exhaust
- changed the clutch and brake levers
- had the rear wheel and tyre changed (double checked the chain slack and it looks to be within the specs in the manual)
- drilled out a stripped allen bolt holding the tacho cable in the tacho drive while it was still attached to the engine

Likeliest culprit seems to be either the rear wheel change or the bad vibrations from drilling out the allen bolt borking something up.

Here's a short video to illustrate:

https://sendvid.com/e64v507i

Thanks!

jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

Is the front gear chain sprocket secure?

MCN · Super Spammer Joined: 22 Jul 2015 Karma :

Does the rear sprocket have a cush drive and or a sprocket carrier bearing.
I'm not going to bother googling your bike for you as I'm on a 2gb limit here and need the data for important shit. 🤣
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

ggr · L Plate Warrior Joined: 01 Jul 2018 Karma :

MarJay · But it's British! Joined: 15 Sep 2003 Karma :

Check chain adjustment and lubricate the gearshift linkage. It sounds like it's clicking fully into first under load, which means you're not quite getting it into gear. Not your fault if the linkage is full of dirt, or the chain is too tight or too loose.
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Sister Sledge · World Chat Champion Joined: 17 Aug 2018 Karma :

You definitely sure the chain is tensioned correctly? Might be the angle but that image of the front sprocket makes it look like the chain is sagging (loose) far too much?
Obviously getting the correct tension can be a nightmare on dual sport or enduro machines and they seem to sag regardless but I dunno - looks loose.
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Grubscrew · Scooby Slapper Joined: 23 Dec 2018 Karma :

I can see the problem me thinks fella.
The chain is riding up over a slight step on the edge of the sprocket then correcting itself as the chain tries to tension, that’ll be the clonk you hear .You’ll find there is a small step on the flat face of sprocket ....remedy... new chain and sprocket kit.
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FJR1300/CBR1000F

ggr · L Plate Warrior Joined: 01 Jul 2018 Karma :

Thanks for all the help!

It looks like it was the cush drive rubbers after all. I took it back to the mechanic that fitted the wheel and they confirmed that the cush drive rubbers are worn. Apparently the rear sprocket should only have 1-2 millimetres of play instead of the 7mm or so of play in the video. Would've assumed mechanics usually check for that sort of thing when fitting a new wheel. Also, I came across this example of a worn cush drive on a DL1000 and my bike has the same level of play:

https://www.youtube.com/watch?v=D03gRtDqZYs

I ordered some new cush drive rubbers so hopefully the problem will be resolved when they're fitted.

Is there a certain trick to adjusting the tightness of the chain on an XT? It has these notched adjustment plates on either side which aren't precise at all: one notch to the left and there's 25mm of slack at the tightest point, one notch to the right and there's 45mm, so it seems impossible to set it between 30-40mm as Yamaha recommends. 25mm was way too tight (bike struggled to shift into second), 45mm felt okay, and the first gear clunk happened regardless. Didn't have the clunk with the old wheel so the chain itself seems healthy.

ggr · L Plate Warrior Joined: 01 Jul 2018 Karma :

Welp, I had the new cush drive rubbers put in and there's far less play in the rear sprocket, but the problem remains.

Any more ideas?

redeem ouzzer · World Chat Champion Joined: 06 Oct 2015 Karma :

On my track bike the problem was the springs in the back of the clutch basket had compressed with age so it had about 1/2" of slop between the clutch outer and the driven gear. Some bikes have rubber blocks instead of springs (bit like the cush drive on the rear wheel), these can degrade over time as well giving the same symptoms.

Just bear in mind that the issue on my track bike got so bad it started missing gears and eventually threw me off......
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