Oil leak from front drive sprocket 750 GT

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jonduc74
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Oil leak from front drive sprocket 750 GT

Post by jonduc74 » Mon Jan 28, 2008 2:44 am

I have a problem with oil leaking form my front drive sprocket, I have replaced the two outer seals and had a new sleeve machined up that goes in behind the sprocket against the main seal. All is fine with no oil leaks, as I know the sprocket nut has to be tight to form the seal.
My problem is that the sprocket keeps on loosening even after tightening it again and again and I am sure it is not the lock tab slipping.
Any help on this would be great thanks John

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jonduc74
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Post by jonduc74 » Mon Jan 28, 2008 2:56 am

Hi sorry I may not have made myself clear, when the sprocket lose this is when the oil leaks from this area!

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BevHevSteve
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Post by BevHevSteve » Mon Jan 28, 2008 8:31 am

hi john, sounds like you need to completely clean everything to remove oil residue, put some BLUE LOCTITE on the threads and tighten everything up. You need to use a proper tool to do this. If you just use a driver to try to tighten the nut.......... the proper tool is a socket with 4 pin that stick out. I am currently out of stock on these but my machinist has promised more for me very soon.
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Post by wdietz186 » Mon Jan 28, 2008 7:55 pm

Jon, I've had the same problem with my 750 too. The oil is coming out from the splines on the sleeve gear. The grooves are cut way back on the gear and the bearing doesen't sit on a solid surface. So the oil goes under the inner race. I fixed mine by sealing the faces of the sprocket and spacer with silicone sealer. That and a tight nut should solve your leakage. Bill

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jonduc74
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Post by jonduc74 » Sat Feb 02, 2008 2:19 am

Hi I don’t how the oil can be coming out from the spines on the sleeve gear, the way I see it is the system is set up via a sleeve which is pressured up between the inner and outer oil seal (the sleeve should not be scored or you should replace) then the way to stop the oil leaking from this point is to make sure the sprocket is keep tight. What I have now done after reading Steves reply and the blue lock tight suggestion, I have removed the lock tab as I found the movement on the inner side of the tab could be what is causing the slight sprocket movement, and also locked up a second nut of the same type to act as a lock nut.

Will let you know how I get on, if this fixes the problem

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Post by baddean » Sat Feb 02, 2008 8:46 am

Hi All,
I've been watching this thread with interest as I have just been in this area on my bike. My sprocket nut runs a little loose with no ill effect and no oil leakage.
I would like some one to explain to me how the sprocket being kept tight keeps oil from getting out. You have an oil seal in the case directly behind the sprocket to seal oil in around the main shaft. If this seal is leaking it will seep oil out in the spline area of the countershaft sprocket.
Keeping the sprocket and nut tight appears to have nothing to do with sealing oil. The countershaft sprocket does not press against anything to effect a seal.
Even if the sprocket were loose on the shaft it is still self centering when the final drive is operating. As the engine pulls the chain around the countershaft sprocket and the rear drive sprocket the front will stay in alignment with the rear. All the nut does is keep the countershaft sprocket from sliding off of the main shaft such as if the chain became too loose.
My Kawasaki EX500 race bike from years gone by had the countershaft sprocket held on with a clip and "floated" on the main shaft splines (as do many modern Japanese bikes).
If someone has replaced the main shaft seal and the leakage returns then this might be a symptom of some thing else that is worn such as a bush or bearing that the main shaft runs in allowing slight movement of the shaft and subsequent leakage at the main shaft seal.
If there is something that I have grossly overlooked here I would appreciate being enlightened.
Dean
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Post by Peter Mille » Sat Feb 02, 2008 11:05 am

My Mille did the same, a few weeks after I got the bike new in 1985.
When I went to the dealer, he tightened the sprocket nut VERY hard, and that stopped the oil leaking.....!!
Last edited by Peter Mille on Thu Jun 12, 2008 10:33 am, edited 1 time in total.

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Post by BevHevSteve » Sat Feb 02, 2008 12:10 pm

i now have the proper tools back in stock to tighten these up
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Post by wdietz186 » Sun Feb 03, 2008 7:45 pm

Jon and Dean, If you disassemble the sprocket and sleeve you will see that the shaft seal runs on the spacer sleeve and not the out put shaft. the oil runs out from under the spacer sleeve due to the roughish surface of the gear it butts up against. Cranking down on the retaining nut will seal if it is a fairly smooth surface but some sealant will insure it won't weep. The correct tool will make tightening much easier,as a hammer and punch usually just tears things up.

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KM7 Sprocket Locknut Torque

Post by stu1765 » Wed Jun 11, 2008 2:16 pm

Hi

I am just getting round to changing the front (countershaft) sprocket on my SSD, also having the dreaded oil weep. I have a new KM7 locknut and the Bevelheaven "tool".

Can anyone recommend a torque setting?

Also is their anywhere that contains general torque settings for fasteners on my SSD?

Stu175
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Craig in France
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How tight is tight

Post by Craig in France » Thu Jun 12, 2008 9:59 am

Hi Stu,

The value given in the workshop manual is 10-12 mKg. But, for this one, better to do as Tony Brancato told me: Forget about torque wrench settings. Do it up as tight as you can ... and then some more. (Note to others: Please DON'T follow this advice if you haven't got the proper tools !)

(Frankly, you ain't going to break or strip anything).

As to the rest: I don't think I've ever seen a list of torque values, like wot Laverda used to usefully provide; just a scattering of references in the workshop manual, e.g. for re-fitting the generator rotor, "... tighten the nut to a torque setting of 10mKg".

S'pose I could go thru the manual one day and draw up a list ... yawn.

But, in practice, you can just use standard values based on the bolt or shaft sizes, anyway - assume 8.8 quality steel, but also have an eye to what the bolt is threading in to, e.g aluminium casings, and perhaps back off a tad. You can always use a thread locker, anyway ...

Ciao

Craig

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