Kr-1s clutch assembly - gear lash

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kiwisteve74
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Kr-1s clutch assembly - gear lash

Post by kiwisteve74 » Sun Apr 12, 2020 7:19 am

Hi Guys

I’ve rebuilt a kr1s engine and with the engine now in the frame I have fitted the clutch basket and found that as I rotate the clutch basket on the shaft I feel a slight binding or scraping but not always in he same spot. like the gear on the back of the clutch is occasionally scraping or binding on something? All spacers and parts are assembled as they should and I assumed it was due to the outer cover not being on and the water pump and kickstart shafts not central. Now with the outer covers on I can actually feel it as I slowly turn the kick start by hand. Anyone struck this? Are the primary gears and the basket back gear prone to lash? This is a rebuilt kr1 crankshaft, I’m assuming the primary gears and cranks are the same for kr1 and 1s?

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Re: Kr-1s clutch assembly - gear lash

Post by kiwisteve74 » Mon Apr 13, 2020 8:58 am

Ok, so I’ve since worked out that when I use the kick starter or try drive the crankshaft with the clutch basket that there is a point that the teeth of the crankshaft and teeth of the clutch are quite noisey like they don’t like meshing. However when I use the crankshaft to turn the clutch like it would when running normally it’s a lot better. Is it possible this is normal as it’s using the wrong side of the teeth when kicking over and the drive becomes the driven. Or should it be perfect? Sorry I’m an Rgv man and I’ve never noticed this on an Rgv, is it common to Kr1s?

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Re: Kr-1s clutch assembly - gear lash

Post by KR-1R » Thu Apr 16, 2020 1:59 pm

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youve not run this motor since purchasing before the rebuild?

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Re: Kr-1s clutch assembly - gear lash

Post by kiwisteve74 » Thu Apr 16, 2020 11:37 pm

Ok, so I have come to the conclusion the primary gear is the problem and although I can’t find any abnormal run out with the crankshaft or the teeth on the primary gear I don’t think it’s normal. I have attached a video link for those that want to see why I’m concerned.

What I have done so far:

Full engine rebuild for restoration with the bare motor only mounted in the frame, new gaskets, pistons, bearings, seals. The only exception being the complete crankshaft removed from a low mileage kr1 motor and swapped directly into the kr1s cases. All spacers and shims are present. I have removed the water pump cover and drive gear, idler gear for the kick start, removed the kickstart shaft and gear, checked the Ballance shaft timing, removed the balance shaft. No fly wheel.

I have placed a black mark on the crankshaft that shows at what part of the rotation the noise / vibration is present when I turn by hand. I have 2 clutch baskets and both do it. It is however slightly less Audible when I use the flywheel to drive the crankshaft but I can still feel it and hear it as it turns. Without the clutch basket the crankshaft feels smooth as it turns without any noise or vibration. To me it is a teeth mesh issue and the two clutches would point toward the primary gear as the problem, any other thoughts before I rip it all apart.

Turning by hand using clutch:

https://www.dropbox.com/s/is1q280yy1zuk ... M.mov?dl=0

Turning by hand using flywheel:

https://www.dropbox.com/s/q8tcsn0tmacf0 ... M.mov?dl=0

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KR-1R
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Re: Kr-1s clutch assembly - gear lash

Post by KR-1R » Fri Apr 17, 2020 12:49 am

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with basket removed but 6th gear engaged
drive the chain Output (shaft) sprocket to cycle the Input shaft

I think extract the gear cassette and inspect and reinsert before getting carried away splitting cases again

the trouble is it appears from videos at same place on crank each time so now thinking crank side
if it was secondary (gearbox) side the noise would be at a different place each time because of reduction ratio

work backwards

flywheel stator problem?
balance shaft? :cry:

easy to take top end back off and pump pistons to rotate crank at speed 1-2 revs per second.
You will feel a knock if its a problem with
crank trueness
flywheel/stator
balance shaft

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Re: Kr-1s clutch assembly - gear lash

Post by kiwisteve74 » Fri Apr 17, 2020 6:58 am

Hey Danny

The clutch basket on its own is sitting on the input shaft via the brass bush and spins freely without tuning the shaft. So I don’t think the gearbox position will matter. I know straight cut gears are noisey compared to helical but I don’t think they should be noisey in one particular part of the revolution. the Primary gear has no bolt so it’s obviously an interference pressed fit. I have another from the worn crank but No way of removing it without splitting cases.

Flywheel and stator not yet fitted, I’ve bolted a metal plate up against the primary gear and measured the gap with a feeler gauge as I spin the crankshaft and it seems to run true. It’s got to be a worn tooth. Who knows, maybe with transmission oil under normal operating conditions it might be fine. I just don’t want to take that chance, but I also don’t want to pull my freshly built motor to bits for someone to say it’s pretty normal with a Kr1s motor, they all do that and it won’t be a problem.

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Re: Kr-1s clutch assembly - gear lash

Post by KR-1R » Fri Apr 17, 2020 8:05 am

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I trust your instinct and mechanical abilities

with the cylinders back off while its still dry assembled

a bit easier with pistons off however...

cycle the crank via conrods determine same point each rotation
eg which cylinder might be culprit
never know something might have fallen in there. eg a BDC problem

sounds stupid too but was squish clearance checked eg a TDC problem
you shouldnt have a noise at 5 rpm - the only thing you should feel is primary compression (unless your spark plugs removed)

i think the manual says crankcase and balance cover are are matched set

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Re: Kr-1s clutch assembly - gear lash

Post by KR-1R » Fri Apr 17, 2020 9:00 am

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saved by the Facebook I guess

goodbye

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kiwisteve74
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Re: Kr-1s clutch assembly - gear lash

Post by kiwisteve74 » Fri Apr 17, 2020 1:12 pm

Not sure I found many answers on FB either mate, I by far prefer the forum environment.
Good of David to put it out there, I’m always fearful of who can and can’t see what’s posted on the old FB but it’s helpful all the same. Will report back once I have another look tomorrow. I just don’t recall replacing parts of the crankshaft but something tells me I ordered crank seals and outer bearings? So maybe I took the pinion off and it hasn’t gone on square or is not sitting where it should? I tried looking at some old pics. It was 2005 I built the motor. Time flys

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Re: Kr-1s clutch assembly - gear lash

Post by James P » Sat Apr 18, 2020 1:00 pm

Steve,

Does a very close inspection of the crankshaft primary gear teeth reveal anything? In the video, the noise seems to be a sort of 'clunk', suggesting that one tooth may be damaged. You mentioned that you could feel the spot at which the crankshaft and clutch basket primary gears bind, so I would expect to see a hint of deformation on one of the crankshaft gear teeth...or maybe even some foreign material stuck there.

Regards,
James

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Re: Kr-1s clutch assembly - gear lash

Post by kiwisteve74 » Sun Apr 19, 2020 9:20 am

Yes james, I’m sure it’s a fault with a tooth on the pinion gear on the crankshaft but I’m yet to check the runout before pulling the cases apart to remove the gear and swap with the one from the old crankshaft. I have inspected the teeth and can’t find anything wrong with the surface or root of each tooth. I can’t of course rule out that a tooth is not bent or twisted. Being cast I guess it’s possible and maybe the gear or crankshaft was dropped? There was talk that the gear may not be on square as the light in my videoclip seems to be flicking as it turns, however I have found the old crankshaft does this also and it seems to be the way the gear has been faced off, the surface is shiny when looking at it in one direction. Unfortunately It was 5 years ago that I built this motor so I just can’t remember. Time will tell when I get a dial gauge.

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