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Discussion Starter · #1 ·
Hi, 2005 klr650 w about 20k. Previous owner explained it leaks oil around the sprocket, and mess shows he was right. I did notice he had overfilled the oil quite a bit. I'm guessing he set the level with the bike on the side stand. I took out a bit, wiped down the mess and don't see any more oil leaking. Haven't driven at any highway speeds yet, so maybe that's a factor. So could having the level too high cause oil to leak around front sprocket without actually having a leak? Some sort of overflow effect? Or am I maybe looking at something intermittent and better off just swapping the seal when I do the front sprocket? Thanks for any wisdom! Dan
 

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That seal can be damaged if the chain is run too tight. Likely cause of the leak.

Tom
 

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+ 1 on a too-tight chain as a likely cause of compromising the countershaft seal. Rule of thumb: Chain slack correct when lower chain links will barely touch plastic on swing arm, unladen bike on side stand.

Over-filling unlikely cause of leak, IMHO, especially at countershaft seal. I think excess oil typically would be blown out crankcase vent into airbox; more-or-less harmlessly.

Corrections and clarifications welcomed.
 

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+ 1 on a too-tight chain as a likely cause of compromising the countershaft seal. Rule of thumb: Chain slack correct when lower chain links will barely touch plastic on swing arm, unladen bike on side stand.

Corrections and clarifications welcomed.
Ok, Clarification I'll offer.

Rule of thumb: Chain slack is correct (when Lifted, the Lower run of chain) links will barely touch (the rear tip of black) plastic (under the) swing arm, unladen bike on side stand (or on a center stand).
 

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Discussion Starter · #5 ·
Thanks guys. Appreciate the input. I'll go ahead and change that seal (doesn't look too difficult) and make sure the chain is not too tight when I replace. The freaky thing is it doesn't seem to be leaking now..... In any case I think the parts for the seal were around $20, so rather be safe than have to take it apart again. Dan


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Ok, Clarification I'll offer.

Rule of thumb: Chain slack is correct (when Lifted, the Lower run of chain) links will barely touch (the rear tip of black) plastic (under the) swing arm, unladen bike on side stand (or on a center stand).
Thanks, Paul!

Your edits improve the clarity and precision of my post, increasing its application to readers of varying levels of experience. I think my original version assumes more a priori reader knowledge and familiarity than might be encountered in some cases.

Much obliged!

----------------------

(Didn't want to get into the true, full, lead-pipe cinch valid method of adjusting chain slack--loosening to permit maximum swing-arm excursion; some other time! :)
 

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It may be well to simply take the bike for a test ride to confirm that it is still leaking at the sprocket seal. I sometimes see "leaks" which turn out to be chain lube in excess, FWIW.

Inspect the sprocket spacer sleeve/seal runs on the sleeve and sometimes dirt wears a groove into the sleeve. There is an "O" ring which seals the inside of the sleeve and is sometimes damaged. If there is a wear groove or dirt build up on the sleeve, that should be addressed by polishing the area with annular action.


Thanks guys. Appreciate the input. I'll go ahead and change that seal (doesn't look too difficult) and make sure the chain is not too tight when I replace. The freaky thing is it doesn't seem to be leaking now..... In any case I think the parts for the seal were around $20, so rather be safe than have to take it apart again. Dan


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Another possibility from my experience is the seal could be working out of its seat. That happened to me 2,000 miles from home. I pushed the seal back in and it is still sealing.

That seal is easy to replace if it is damaged. I am more concerned about the damage a tight chain can do to the countershaft bearing, the wheel bearings and the chain itself. These are all steel with no give while the seal is rubber and spring with a little give.
 

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Discussion Starter · #9 ·
Hi guys-chain seems about right. May have been tight at one time when new though. When I put things back together I'll make sure not too tight. This things was covered with oil, so definitely leaking at one time. Just weird it doesn't seem to be leaking since cleaned it up. Maybe the seal was poor at one time and then reseated? Unlikely I know. I'll let you know what I find when I get it apart....


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Gomotor: I don't think the issue of potential damage to the output shaft bearing can be repeated often enough.

I know that you have much experience so wonder if you would be prepared to speculate as to whether internal crankcase pressurization might have been the culprit? That's the only consistent mechanism I have witnessed with regards pushing out seals. Honda Civics were famous for that when I was working in Yukon and we developed a quick fix to prevent pressurization.

I'm trying to find more time to get back to testing internal pressure at this time. I have a vacuum pressure gauge plumbed into a metal oil filler plug and have found up to 1-1/2 PSI of pressure build up at WOT on back country roads. Haven't taken it onto the highway as yet since have been testing some other numbers also.

My bike has the orifice in the air box reamed to 3/16" or 1/4" so build up will not be as marked as with the original orifice. I have found a restrictor of the same relative size as the original hole and will place that into the vent hose when family health issues subside.

Any chance anyone could plumb a vacuum pressure gauge into their system to provide more numbers? My engine is quite tight so not seeing much blow by. When Paul was talking about oil throw off, during the earlier stages of his investigations, I can recall that we discussed crankcase air density and venting but haven't heard of anyone doing any measurements so thought to ask.



Another possibility from my experience is the seal could be working out of its seat. That happened to me 2,000 miles from home. I pushed the seal back in and it is still sealing.

That seal is easy to replace if it is damaged. I am more concerned about the damage a tight chain can do to the countershaft bearing, the wheel bearings and the chain itself. These are all steel with no give while the seal is rubber and spring with a little give.
 

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........................wonder if you would be prepared to speculate as to whether internal crankcase pressurization might have been the culprit? ..............
I think my seal working out of its seat was just a random event. I just pushed it back in with my thumb. The bike had around 80,000 miles then with 40,000 of that on a 685 piston and another 20,000 since with no problems before or after. The crankcase vent is stock.
 

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Maybe simply the rubber jacket hardened and shrank?



I think my seal working out of its seat was just a random event. I just pushed it back in with my thumb. The bike had around 80,000 miles then with 40,000 of that on a 685 piston and another 20,000 since with no problems before or after. The crankcase vent is stock.
 

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A mistaken notion once held: A check valve (PCV valve or some implanted reed valve) in the crankcase ventilation line would result in crankcase vacuum; however . . . the premise has never been confirmed by competent and repeatable testing of which I'm aware (it may exist). A test program reported on .net, with a pressure/vacuum gauge teed into such a line, measured positive pressure continually in the crankcase of a running engine, check valve or not. Exception: A momentary vacuum was measured, only during periods of extreme deceleration.

Haven't read much about the, "PCV Valve Mod," on Internet websites lately.
 

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A mistaken notion once held: --------------- Exception: A momentary vacuum was measured, only during periods of extreme deceleration.

Haven't read much about the, "PCV Valve Mod," on Internet websites lately.
Thank goodness for small favors.
 

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I happen to have one with the hose off the nipple on the air box right now. Is that the nipple your asking about? A 3/16" bit went in. 7/32" would not go. Both of my bit sets were missing 13/64" bits. So, I am going to call it 13/64" or 5.15mm. Do I need to go get a 13/64" tomorrow?
 

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Discussion Starter · #18 ·
Got this one fixed by changing the seal and o-ring on the drive shaft. The old ones looked ok, but can't always tell by looks I know. I did notice the bendy washer that holds the nut in place over the drive sprocket was completely trashed and not fitting over splines correctly. Maybe this was allowing things to wiggle and vibrate a bit causing seal to leak. Just speculation, but in any case I think all set. Thanks to all for your comments.


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