Knocking noise under load.

[Lord Percy]

My bike's making a gentle knocking which I can feel in the frame when riding slowly.


Here's some evidence I've gathered which may help with diagnosis:

1. The knocking is well-timed, as if there's some relation to the chain or wheels.
2. It only happens under load. So no problems when on its stand, and nothing when the throttle is closed.
3. It only happens after a bit of riding when the machine has warmed up a bit.


Things I've checked:

- The sprockets and all the teeth are fine.
- Chain doesn't have any tight or slack bits.
- Rear wheel is aligned.


Thoughts?

Thanks.

[Hawkeye1250FA]

Have you tried running it on the centre stand in 1st gear? That should help you pin point whether its a chain issue or wheel issue (Or other).

That way you are off the bike and closer (not too close! ) to the source of the sound.

[MarJay]

Telling us the make and model of bike might help a fair bit...?
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Lord Percy]

[Hawkeye1250FA]

You said "stand" (i read that as side stand)

Bike on Centre stand in 1st gear with bake wheel being driven by the engine would class as under load in my book?

So if the knocking is not present in this situation I would be tempted to check the front wheel.

[MarJay]

https://s2.quickmeme.com/img/8a/8a4bd63b92aa20a7480e266ab2a663dbcaac4fd3ee37fd36e143696223b07264.jpg
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Lord Percy]

[Kris]

Chain tension?
____________________
NSR125RR - ZXR750H1 - ZX9R E1 - GSF600S - GSF600SK3 - VFR400-NC30 - SV1000N - ST1100-R - CBR900RR-R - GSF1200SK5 - GSF600SK1 - VFR1200FA - GSXR1000K2 - ZZR1400 D8F
www.prisonplanet.com

[Hawkeye1250FA]

I'm getting bored now.

So have you or have you not tried it on the Centre stand with the bike running in 1st gear?

[Lord Percy]

[Lord Percy]

[Baggyman]

[Baggyman]

Also, check the engine mounts are tight
____________________
Old fart
Baghira, modded GS1000 and the T150 I bought in 1978 when I was 21

[Lord Percy]

[bladerunner]

I've had a shop fit the back wheel spacers in on the wrong side causing simmilar issue....and I've had a link crack a sideplate causing the same thing...i rode 100 miles on the Damn thing be for spotting the problem after decreasing the whole chain off the bike!!!! The split was on an inside plate 🤔🤤🤤
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[Lord Percy]

Reattaching the exhaust did nothing to help the knocking noise problem

I've had another look at the chain and I think actually it is getting near to replacement time.

However, I think the knocking sound is something more sinister. I've noticed it doesn't increase with speed, it increases with revs, and only under load, which to me says it's something to do with the inside of the gearbox.

Beats me what could be causing it though. Never really looked in a gearbox before.

It sometimes slips at high speed around 5000 revs so I know the gearbox has a problem anyway, but the slipping has been a constant and unchanging thing for ages. Would there be a link between that and this new knocking noise?

[Robby]

Traditionally a knock that increases with engine speed and is more pronounced under load means fucked crank bearings. Has it been run out of oil recently?

[Lord Percy]

[Lord Percy]

[Robby]

I'm not sure, I've only come across properly fucked crank bearings once, and it was on a lawnmower. That was just knocking in time with the engine.

Does the noise go away when you pull the clutch in?

[Lord Percy]

[Robby]

If it was a knock at idle that goes away when you pull in the clutch, then I would look at carb balancing - if the carbs are out of balance then one cylinder is making a little more torque than the one next to it, and this shows up as clutch noise. Instead of getting smooth, even power its getting lumpy power, and this makes it shake and rumble.

If the carbs are way out of sync, or the valve clearances are different across the pots - which gives the same results - then you can get rough running. I would check the valve clearances and balance the carbs as part of routine servicing.

If the problem is any deeper, then I would just live with it until it breaks. It's a divvy, engines are cheap and no-one likes them.

[Stalk]

Had the same problem with the same bike a few years ago. The noise and vibration stopped when the split link in the chain snapped. Has it got a split link? And has it lost its o rings?

[Lord Percy]

[Stalk]