Clunk from left side / rear when letting clutch out?

[Antarius]

I've recently noticed a "clunk" like sound when rolling from a stop or very slow start, just as the clutch gets completely let go. The chain is due, and is loose, but I'm curious if you guys have any other ideas (more serious) than a simple chain replacement? I've already tightened the chain once and it's loose again within 500 miles, so I'll be replacing it and the sprockets soon.... but the clunk is rather, uh, noticeable. I can basically feel it in the pegs as well as hear it.

What do ya'll think?

 

[Scorpuco]

Same clunk we all get when getting into first gear? I'm not remotely technical, but wonder if is it a 'clutch' issue or a 'first gear engaging late' issue...

 

[Old Can Ride]

I've recently noticed a "clunk" like sound when rolling from a stop or very slow start, just as the clutch gets completely let go. The chain is due, and is loose, but I'm curious if you guys have any other ideas (more serious) than a simple chain replacement? I've already tightened the chain once and it's loose again within 500 miles, so I'll be replacing it and the sprockets soon.... but the clunk is rather, uh, noticeable. I can basically feel it in the pegs as well as hear it.

What do ya'll think?

Usually the chain needs to be adjusted and lubricated. However, wore out chain does make the same noise. That noise does sound like your clutch has something wrong with it, but it is the chain.

 

[Antarius]

Same clunk we all get when getting into first gear? I'm not remotely technical, but wonder if is it a 'clutch' issue or a 'first gear engaging late' issue...

Hah, no no. Not when putting in gear, just when rolling.

Usually the chain needs to be adjusted and lubricated. However, wore out chain does make the same noise. That noise does sound like your clutch has something wrong with it, but it is the chain.

Yeah that's what I figured. The clutch is working fine, not slipping or anything, I figured it was just the chain slapping the swing arm and/or making noise. No worries, it'll get replaced.

 

[Harald]

Sounds like a too loose chain or possibly a chain with stiff links (that causes the chain to alternate tight and loose as it rotates around the sprockets). In either case, the chain hits the swingarm and clanks (or is clunk a better word? ). I would caution against over tightening chains for normal adjustments because this will accelerate wear. I've worn out chains by overtightening them and now err on the loose side of the normal range for adjustments.

Before the NC, my last chain drive bike was a very powerful Honda CBR1100XX that was still on it's original chain at 35,000 miles when I sold it. BTW, I was very diligent about lubing it regularly with nothing other than WD40.

 

[Antarius]

Sounds like a too loose chain or possibly a chain with stiff links (that causes the chain to alternate tight and loose as it rotates around the sprockets). In either case, the chain hits the swingarm and clanks (or is clunk a better word? ). I would caution against over tightening chains for normal adjustments because this will accelerate wear. I've worn out chains by overtightening them and now err on the loose side of the normal range for adjustments.

Before the NC, my last chain drive bike was a very powerful Honda CBR1100XX that was still on it's original chain at 35,000 miles when I sold it. BTW, I was very diligent about lubing it regularly with nothing other than WD40.

The NC runs a 520 pitch chain, which is much thinner than the 530 or even 535 that was on your CBR1100xx... which coupled with good maintenance equates to quite a long life.

The NC's low quality crap RK chain, plus its light pitch (520) don't have that luxury. I've always found that OEM chains (especially RK chains), once you adjust them.... its a losing battle. Especially RK chains in 520 pitch.

I'll be putting a quality DID 520 ERV3 or something similar on the NC and I expect to get well over 15k out of it, probably more like 20k. I hate RK chains, always have, always will -- they always do what this RK has done on the NC. They get a little sloppy, you adjust them, and boom its game over. From that point on you're constantly having to adjust it because it continues to stretch.

 

[L.B.S.]

Check the rubber cush dampers in the rear hub when you replace the chain and sprockets.

With the bike sitting still and not running, can you rotate the rear sprocket to any noticable degree forward/backward? It should have a little bit of a rubbery wiggle, but not very much. If you can wiggle it a fair bit, then it might be worn rubber baby buggy bumpers in the hub.

Have you taken off the rear wheel and/or rear brake caliper ever? If caliper not engaged in it's slot on the swingarm, it can produce clunks (and potential great havoc!)

Axle tightened to specs?

Is your "clunk" a deeper tone, or a higher tone? I would term a higher tone noise a "clink" versus a lower tone "clunk" (or "thud") If closer to a clink, check the metal plates at the ends of the swingarm where the chain adjuster bolts go through. Even with tightened chain and axle, they can not seat properly, and make noise and rotate around, the left side one can get hit by the rear sprocket bolts and make a clatter/clink/clunk noise.

A slow noise once per revolution? Multiple times per wheel rotation?

 

[pconn]

Antarius,

I had a very similar issue for a while when I first got my bike. Almost every time as I started out from a stop, I heard this "thunk" sound coming from down and to the left. It turns out, the "solution" is a bit embarrassing. After several inspections, complaining to my mechanic, and testing a few things, I realized that as I was starting out, I was briefly delaying lifting my left foot and as the bike started to roll forward, the spring-loaded footpeg was raising up as it came in contact with my leg. Once I lifted my foot up, it dropped back down into position, making the "thunk" sound. I felt really stupid telling my mechanic

 

[StratTuner]

I too suffered the clunk sound. Have you had the rear wheel off ever?

The rear brake caliper clamps on the rear disk.
It has a slot that fits over a bolt on the swing arm.

It's very easy to reassemble the rear brake WITHOUT matching up that slot with the swing arm bolt.

Try this:

sit on the bike, apply the rear brake gently, roll backwards.

If the rear caliper is anchored to the swing arm slot, the caliper will remain stationary.

If the rear calipr rotatates backward with the disk then it's NOT anchored in the slot. (caution. you can tear out your rear brake lines doing this).

The "clunk" sound I was hearing came from the rear caliper rolling back a little on the rear disc. When I'd start out, it would rotate forward and hit the swing arm bolt... making that noise.

Remedy? take the rear wheel off. (the rear caliper will fall off when you do...that's how this happens).
examine the caliper for the slot and the examine the swingarm for the bolt head that goes in the caliper slot.
MAKE SURE THE SWING ARM BOLT HEAD IS IN THE CALIPER SLOT.
This will keep the caliper stationary and stop that sound.

Keep in mind. The rear brake still works when the slot/bolt aren't seated. That's a good thing, but check for the caliper going backwards with the disc when you roll it backward gently.

 

[Antarius]

It's definitely a deep thud, not a clink.

And I'll check the caliper now!

Edit, caliper is installed properly. I'm gonna say its the chain

The noise goes away once you get up to speed. It's just at that transition when you first get going - just as you fully disengage the clutch.

 

[L.B.S.]

It's definitely a deep thud, not a clink.

And I'll check the caliper now!

Edit, caliper is installed properly. I'm gonna say its the chain

The noise goes away once you get up to speed. It's just at that transition when you first get going - just as you fully disengage the clutch.

You tried to wiggle the sprocket back and forth at all?

 

[StratTuner]

It's definitely a deep thud, not a clink.

And I'll check the caliper now!

Edit, caliper is installed properly. I'm gonna say its the chain



The noise goes away once you get up to speed. It's just at that transition when you first get going - just as you fully disengage the clutch.

well... i'm glad you checked it. It's an easy one to miss.

 

[Deleted member 1183]

If closer to a clink, check the metal plates at the ends of the swingarm where the chain adjuster bolts go through. Even with tightened chain and axle, they can not seat properly, and make noise and rotate around, the left side one can get hit by the rear sprocket bolts and make a clatter/clink/clunk noise.

Interesting suggestion. I have had a low repetitive knock from the left side particularly when starting off from cold, but it more or less disappears when everything is up to operating temp. Its frequency for me has possibly coincided with each revolution of the chain. I had put it down to tight links. The sprockets are ok and the chain length is ok and the tight spots are not overly tight. I will now look at the adjuster on the left side and the cush rubbers as suggested elsewhere above. My current mileage is 21,000Kms equating to about 13,000 miles. If neither of the above is responsible then I will revert to the tight link theory. Yes I agree the 520 chain is a bit on the light side.

 

[Antarius]

You tried to wiggle the sprocket back and forth at all?

Yeah, the cush drive is fine.

 

[CaptDL]

I've got it. Thought it was just my lousy shifting after being off a bike for several years. On almost every upshift there's the normal upshift snick then another as the clutch fully engages. Been writing it off as bad form but... there's something else going on.

 

[Antarius]

Mine was the chain....

 

[Deleted member 1183]

I have checked the Adjustment plate as suggested. I have also had the wheel off and the cush drive rubbers seem ok. The brake caliper is properly seated. The chain is within wear tolerances but there are one or two tight spots in it. Again they are not excessive and the chain is well lubed at all times. The sound is barely audible most of the time and almost disappears completely when the chain is about an hour into a journey. However I recently washed the bike and this entailed the use of a degreaser around the swingarm and other greasy areas (from the chain lube) . Inevitably that stuff got onto the chain. Sure enough riding the bike just after the wash, the knock was considerably louder. As the Tutoro did its job the knock went back to its previous levels. Imho the sound has to be the chain tight spots, made more audible by the quietness of the engine.

 

[kharli]

its a set of loose links can cause nasty clunking, not as easy to spot as tight links. (I thought my gearbox was tearing itself up at one point !) especially with slightly worn front sprocket.

 

[L.B.S.]

Huh! Thanks for the noise feedback, fellows. It's always good to squirrel away more little notes and potential causes for stuff that puzzles you! I can't say I've ever really experienced a link-derived clunky noise from any of my chains ever, so it's not something that would have ever ocurred to me

 

[Deleted member 1183]

Update.

Today a new chain was fitted. The irritating knock is gone. Whether it was a tight link or a loose one was never discovered, as it was not obvious. I did notice however that the engine sprocket remains floating on the splines of the shaft, even with the bolt tightened to the full torque against the washer. It is meant to be like this per my trusted Technician. Imho that looseness of the sprocket on the shaft would tend to amplify any tightness or looseness of a link when passing over it, and transmit the sound into the gearbox. As I said, the sound is now gone. However there were only 13,000 miles on the old chain and sprockets. Neither the chain or the sprockets were worn out but my Tech advised me to replace them anyway in case there was a weakness on the chain that could break it. The new chain is seriously more robust than the original. I would normally expect to get around 20000 miles from an Xring chain, especially from such a low powered bike. That remains to be seen.......