Oil Leak around front sproket

[Jeffy]

Hey,

First Post!

Recently swapped out the 530 chain and sprocket set for a 520 set. now when running i get a little bit of an oil leak. I tracked it down where the transmission output shaft meets the sprocket.

I *think* what's wrong can be attributed to me having about 1/16" wiggle in where the sprocket sits on the shaft. I went digging around thinking that maybe i forgot to purchase a spacer or bought a sprocket designed for a different set up, but after talking with MikesXS (and despite the indications on their website that the spacer is sold separately) there is actually no spacer needed for this setup.

Then I thought maybe I simply didn't tighten everything down correctly. So after another attempt at tightening it all down and still having this space, i took calipers to it. Measured the shaft, measured the recess in the nut, measured the thickness of the lock washer and the sprocket and right there in the numbers was the 1/16" of extra space that shouldn't be there.

Based on the amount of grime that was under the cover when i got this, I don't think this motor has ever been apart besides at the factory. My thought was that maybe the PO did some handy-man work in the transmission and left out some "unnecessary" parts during a rebuild. But, based on the quality of workmanship of the rest of the various hack-jobs on this bike, i suspect had the transmission been taken apart, it'd still be in pieces in his garage.

I've been digging around the forum looking for anyone that may a problem like mine. it appears from both here and my conversations with MikesXS that i truly am in a minority with this and i'm totally stumped. I've debated just buying a few of the lock-washers and stacking them up, but this is likely the wrong answer.

Anyway, if you've made it this far, thanks for reading and thanks for any and all advice you may be able to give.


Jeff

 

[jd750ace]

If a 530 sprocket is not torqued down, they weep, or at least mine did, and others report the same. I'd go with a proper spacer. Not sure if it loads the face of the seal and swells it, but that's why I suspect it leaks if loose.

 

[Jeffy]

Does that also apply to the 520? I'm running the 520 now, it was fine when the 530 was in.

 

[jd750ace]

Yes, specific to the 520. It's thinner than the 530 and does not clamp up on the shaft the same. Some "generic" 530s have an issue too.

 

[pereiracycles]

If you've got play, not only will it leak, but it's going to make noise and eventually wear prematurely. Get or make a spacer and the leak should go away.
-Tony

 

[peanut]

Hey,

First Post!

Recently swapped out the 530 chain and sprocket set for a 520 set. now when running i get a little bit of an oil leak. I tracked it down where the transmission output shaft meets the sprocket.

i took calipers to it. Measured the shaft, measured the recess in the nut, measured the thickness of the lock washer and the sprocket and right there in the numbers was the 1/16" of extra space that shouldn't be there.




Jeff

I found exactly the same measurement yesterday Jeff when I refitted my original 530 sprocket . There is a gap on that too! why I don't know but I thought it odd myself and looked around for another spacing washer but there was none.

Re your oil leak I suspect that the culpret there is simply changing your chain.

The increased strain put on your bearing and oil seal from adjusting your new chain up tight has probably been the final straw for your original bearing and oil seal.

I see it all the time on the Porsche forums where folk replace their cam and alternator belts and within a week or two their water pump and alternator bearings give up the ghost due to the sudden increased tension

 

[5twins]

The sprocket needs to be bolted on tight, very tight, like 90 ft/lbs tight, if you expect it to seal. If your mounting nut is tight but the sprocket still moves around, it's gonna leak. The oil seal works against that sleeve that slides over the splined shaft. That's all it seals. The rest of the sealing is done by having the nut very tight. The sleeve hits against the inner race of a bearing inside the motor - metal to metal contact. The back of the sprocket hits against the sleeve - metal to metal contact. The lock washer and nut press against the front of the sprocket - again, metal to metal contact. To seal the inner end of the sleeve against the bearing race so no oil can get by and flow out between the shaft and sleeve, this whole stack of parts has to be pressed in there very tightly.

 

[peanut]

I'm not sure about this.

if the splined section of the shaft is say 30mm long and the sprocket and washer only measure 27mm how does tightening up the lock nut help to compress the shaft 3mm ?

My sprocket doesn't appear to have any play now it is tightened but I can't see how the excess 3mm has compressed, unless tightening the sprocket locknut has driven the sprocket further onto the splines than is possible by hand pressure I suppose

 

[Jeffy]

The increased strain put on your bearing and oil seal from adjusting your new chain up tight has probably been the final straw for your original bearing and oil seal.

While you very well may be right, the sheer volume of oil that's coming out of there would suggest that if it were simply the bearings it would be visible to the eye. i mean, it's dripping fresh oil and fast! (ran it for 30 sec and had a sizable puddle underneath) It's a lot more oil than i would expect to squeak by a cooked oil seal, but just for safe measure, i think i'm going to buy a set and see if it helps (at the least, it couldn't hurt).

I found this while digging around the intertubes

Steel 520 x 17 Tooth Front Sprocket Lighter Weight and more chain clearance for your 650
(Note: Must use with 520 chain and rear sprocket)
*** this sprocket does not have a thicker center and needs shims to modify

https://www.mikesxs.net/product/22-1617.html

This is the sprocket i have. They directly call out the fact that this sprocket does not have the raised center, so perhaps this is simply what i'm dealing with? I've spent the last 1/2 hour digging around the internet looking for a shim/spacer for this, anyone have an idea of where to get something that would do the job? Maybe this is simply a crap sprocket and i need to find one with the raised center?

The sprocket needs to be bolted on tight, very tight, like 90 ft/lbs tight, if you expect it to seal. If your mounting nut is tight but the sprocket still moves around, it's gonna leak

I'm looking into this now, but based on the amount of space that's left, i can't see how the tightness of the nut is going to change it much, but perhaps i've got some worn/mangled threads close to the bottom of the shaft that tightening down with a torque wrench would clean up. Although, FTR, i previously tightened with a big-a$$ crescent with the motor in gear and the chain on to help hold everything still, so it's not just hand-tight.

 

[5twins]

There's only so many threads on the shaft so the nut is only going to go on so far. With a 520 sprocket, you need a spacer washer or a sprocket with the center machined thicker to equal the thickness of a 530 sprocket. Frankly, I don't know why people bother with the 520 conversion. If you were racing, the small weight savings may amount to something but for the street, it means nothing. Add to that the fact that since all the parts are physically smaller with less contact area between them, they will wear out faster than a 530 set-up.

 

[TwoManyXS1Bs]

Like 5Twins posted, the sprocket MUST press against the inner spacer so it can press against the inner bearing face and seal the possible passage of oil under that inner spacer and out the splines. The sprocket nut MUST press against the sprocket to do this, not just tighten on the end of the threads. So, you need an appropriately sized spacer to accomodate the thickness difference between the 530 and 520...

 

[gggGary]

Bit of a heads up;
When assembling the sprocket on the shaft, correct positioning of the fingered washer is critical. It is easy to get it "off register", the nut will try to mash the inner tabs and seem like it's tight but the sprocket will still be loose and the shaft will leak like a sieve.

 

[Brian902]

That is what I was going to mention Gary, the locking washer takes up some space and is required to get everything tight.

Perhaps some are missing the washer.

Peanut, you started with a basket case, did you have one in the basket?


Thanks 5Twins.

 

[peanut]

yes ...I flattened and refitted the original lock tab washer

 

[XSLeo]

Ok the size designation of a chain like 530, each digit means something. The first is the pitch of the chain, this is the length of the links from pin to pin. The second digit is the width of the chain between the side plates of the links. These digits are how many 1/8's of an inch the chain is. The third is to differenciate a motor cycle chain from an industrial chain.
In 530 chain the 5 is 5/8 inch, the 3 is 3/8 inch.
The stock sprockets are 3/8 inch thick to fit the chain. The shaft, nut, lock washer is designed to work with a 3/8 inch thick sprocket.
On a 520 chain the 5 is 5/8 inch, the 2 is 2/8 inch. Or 1/4 inch.
520 sprockets are often built 3/8 inch thick in the center, but 1/4 out for the teeth.
This type sprocket go on to replace a 530 with the thicker part on the out side. This lines up the front and rear inline.
On the sprockets that are 1/4 inch thick all the way from teeth to the center need a 1/8 inch spacer on the out side to make up for the difference in thickness. 3/8 - 2/8 = 1/8.
So if your run a 520 sprocket with out the thicker center you need a 1/8 inch spacer on the outside.
You may have measured 1/16 inch but you need the 1/8 spacer to ensure you don't bottom out on the shaft before the nut gets tight.
Leo