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Discussion Starter · #1 ·
Does anyone experience this as well ? It seems that when the wheel starts to slip partially under load i get knocking sound from the engine. It happens when the revs are under 3.5k on gravel/sand. On asphalt i can floor it at 2k rpm and no noise, on gravel it sound as if it will self destruct. I would think it's the transmission but countershaft, sprockets and chain are new. It only happens with lower traction, sand or gravel road. No wheelspin - no noise. Wheel bearings seem fine as well.
Any ideas ?
 

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Re read this a few times and still trying to imagine the bike under 3.5k, loaded (powering on), and (what gear?), and starting to lose traction: and then you get your 'knocking'?
So, a pre ignition knock? Pinking? Or physical knock/clonk/mechanical noise?
Feel it in the bike when it knocks?
Apologies, but that's going to be difficult to diagnose with words.
New chain etc. may rule out chain whipping. Rear bushes?Spring/ damper unit bushes ok?
Is the bike upright and in a straight line when this happens?
Transmission wise, if you're getting wheel spin, then it's clearly pretty strong through the clutch and gearbox, enough to fire off the tyre anyway. Is the tyre spinning on the rim?
Look for the easy things first like engine mounts and all driveline fasteners. If it's happening at the point of losing traction, everything is pretty taught.

My thoughts...hope it helps.

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Discussion Starter · #6 ·
Thanks for replies guys.
Re read this a few times and still trying to imagine the bike under 3.5k, loaded (powering on), and (what gear?), and starting to lose traction: and then you get your 'knocking'?
So, a pre ignition knock? Pinking? Or physical knock/clonk/mechanical noise?
Feel it in the bike when it knocks?
I heard it in lower gears (1-2-3), but I think it's happening in all gears, usually not much wheelspin in 4th or 5th.
It's definitely not preignition, heard that one before. Something like mechanical hammering, not in sync with the engine speed nor wheel speed , just random knocking.
It stops when rpms get higher or I go smooth on the throttle, or if the traction is lost (maybe it's just rpm's being higher under wheelspin) .
Apologies, but that's going to be difficult to diagnose with words.
New chain etc. may rule out chain whipping. Rear bushes?Spring/ damper unit bushes ok?
Bushes were fine last time I checked, suspension is quiet under all other conditions,. I feel I always had this knocking, and since then I have overhauled pretty much the whole bike. I have a new output shaft and new clutch basket springs.
Is the bike upright and in a straight line when this happens?
Not necessarily. Usually yes with my riding :D
Transmission wise, if you're getting wheel spin, then it's clearly pretty strong through the clutch and gearbox, enough to fire off the tyre anyway. Is the tyre spinning on the rim?
Look for the easy things first like engine mounts and all driveline fasteners. If it's happening at the point of losing traction, everything is pretty taught.
Don't think the tire is spinning on the rim. The bolts are tight.

It sounds like there is some backlash somewhere, some freeplay.
From all the symptoms I would suggest looking into suspension to myself, but that would be heard in other circumstances as well ( I guess ).
I was hoping it was a known problem, and somebody had a ready answer .
 

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Discussion Starter · #7 ·
Chain guides OK? Look for witness marks from chain?
Chain guides replaced not so long ago, chain not to tight, checked with the shock bolt removed.

My opinion is you may just be lugging the engine in too high of a gear. Drop down a gear and ride through that same section...does the sound go away?
It doesn't go away, unless rpms go past 4k-5k. Rpm figures are not exact, but knocking stops with higher rpm's.
 

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My opinion is you may just be lugging the engine in too high of a gear. Drop down a gear and ride through that same section...does the sound go away?
Had that wonder too.. 3k revs and loading it, and it will complain. Really quite bad for the engine too.

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2003 Honda XL650V Transalp
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As my '03 Transalp XL650V has aged I've realised that I need to keep it above 3000rpm or it will develop a "chatter" through the drive train, though this inspired at around 2500rpm when ity was newer. What you're describing sounds a bit like that.
A mate has shown me marks in the clutch basket of a Ducati he bought that had been lugged around in too high a gear by a previous owner.
All that said mine has done about 190,000km with the only engine work being cam chains and clutch plates and springs changed.
 
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