leaking crank seal

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15073jrmd

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May 13, 2009
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hi everyone
i have an ongoing problem regarding a leak from the crank case into the primary case. I have replaced the seal at the crankcase and put everything back together but alas the leak continues. perhaps it is a slightly worn crank, but i don't want to split the cases as the engine is running absolutely superbly and if it aint broke don't fix it. any ideas of what can be done to remedy this situation? perhaps an oversized oil seal? any ideas or feedback welcome.
ps i was going to fit a one way valve to reduce the leak but have been advised not to mess with the oil lines.
 
Fit the one-way breather valve.

It is NOT fitted to an oil line, it is fitted to a BREATHER line.

It should cure your issue.
 
sorry yeah it should be fitted to the breather line, however, i have been told not to mess with this as any tampering can result in catastrophic engine problems. would like to hear your opinion before i go ahead.
 
A one-way breather valve CANNOT harm your engine, even if it's installed backwards.

The catastrophic failure possibilities exist when dealing with ANTI-WET-SUMP (anti drain-back) check valves installed in the main oil line from the tank, that keep the engine from wet sumping due to oil leaking past the pump when the bike sits.

Two totally different issues.
 
The cause of the oil leak into the primary from the crankcase is, in all probability, is caused by crankcase pressure. Eliminate the pressure and you will eliminate the oil passing from crankcase to primary. As Paul posted, a one way breather or PCV valve will do the trick. There are many posts on this site addressing the issue.
 
thanks fellas,
any photos of how you've fitted such an item
i have a post market yamaha item as i've read here that it's the one to use
thanks again
chris
 
have fitted the after market xs 650 one way valve to the breather pretty close to the engine. started her and warmed her up with no leak evident so far. will take her out for a good run when the weather fines up and will get back to you with the results. wish me luck.
regards
chris
 
A one-way breather valve CANNOT harm your engine, even if it's installed backwards.
Click to expand...
Try it sometime for a laugh and see what happens!!! It may not destroy the engine but if you have no other breathers just imagine what's going to happen.
I made that mistake many years ago when I replumbed my one way in a hurry to get on the road and the white exhaust smoke after 3 miles was something else, as well as oil p***ing out of the case to barrel joint. Twas a Combat with the rear breather capped off and no rear pickup modification at the time but think you'll find the same with any 'sealed' system.
 
I had a breather stick closed (not the Yamaha type!) and couldn't work out where the oil was coming from....not torrents by any means, but an oily boot at the end of each race for sure! Bulled the breather apart and let it run straight to atmosphere and that cured it.

To be honest, the only oil leak I ever had was from a cracked rocker cover which opened up when the motor got hot....and no pcv valve would have stopped that
 
Here's a pic of the XS PCV valve. If I were to do it again, I would mount it closer to crankcase. The CNW PCV valve is probably a better choice.

leaking crank seal
 
thanks for the photo jim
i have my pzon lecy ignition and mini coils in that spot
i've hooked up the pcv to the breather line 2 inches from the case and not mounted to anything.
its just held to the breather line with jubilee clips and seems to be working out fine.
will keep you informed as to how its all working out.
thanks for the feedback
regards
chris
 
Probably not totally OT but I saw an entry on the NOC site recently (new forum) and the recommendation was that one way breather valves cause the engine to create such vacuum that the tappets are pulled down by force and rapidly wear the cam!! Also the vacuum sucks air past the crank seal and can suck gear oil into the primary. I could kind of see where he was coming from but enough vacuum to load the cam and tappets more than the 200lb open spring pressures?? And gear oil migration? I think the high gear felt washer might prevent a vacuum being effective. There is some good stuff on NOC tech files but that kind of mis-information puts owners off enjoying the benefits of these mods.
 
it really is hard who to believe
a lot of people swear by thus xs 650 after market piece, otheres recommend the cnw thingee ( i aint got that sort of bread). then there are others who say don't do anything. i'll see the results after a proper run i guess. if it was easy the commando would'nt give me so much satisfaction.
cheers
chris
 
Whoever wrote that on the NOC site must of been missing the day they taught physics in school. Like there are not enough old wives' tales about Nortons.
 
Check the alterator stator studs, oil can leak along the threads, they'll just need loctited in.

Cash
 
I had this problem for a while (on a very high mileage motor) several crank seals and PCV valve later I found out the crankcases had horizontal splits starting from the bearing housing. All welded up and fine now though!

Thats an extreme example and not normal with road motors BTW ! :lol:
 
15073jrmd said:
hi everyone
i have an ongoing problem regarding a leak from the crank case into the primary case. I have replaced the seal at the crankcase and put everything back together but alas the leak continues. perhaps it is a slightly worn crank, but i don't want to split the cases as the engine is running absolutely superbly and if it aint broke don't fix it. any ideas of what can be done to remedy this situation? perhaps an oversized oil seal? any ideas or feedback welcome.
ps i was going to fit a one way valve to reduce the leak but have been advised not to mess with the oil lines.
Click to expand...

Same people hi-jacked me when I had this problem :) Although the XS650 breather is a good thing, it didn't solve my leaking crankshaft seal at the primary case. What did is using a rubber surrounded seal instead of the metal type. The problem was not the seal at the shaft, rather the seal with the crankcase. If you do use the metal type use some sort of sealer such as locktite. Incidently when I took the last metal type out it was already a loose fit to the case and had maybe 500 miles service.
 
I'd say you had two problems contributing to the oil leak. One, the oversize hole for the seal, the other being crankcase pressure.
 
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