Gear oil migrating to engine oil side. (anyone ever see this?)

After a oil/gear oil/filter change, I get in one 40mi ride, check the levels and all are good. A few miles into the next ride, checking the engine oil and it's overflowing. Has anyone had any experience with this situation? Hoping there is only one seal where this could occur and it's not a "split the case" situation. Advice appreciated.

 

Ron

Ron,

 

Seal on the balancer shaft will let oil back into the engine side.  It's under the left crankcase cover.

 

But with that said, couple comments:

 

1. Make sure your tranny vent lines are not plugged.

2. Make sure it's really coming from the tranny; where is the level at there?   Oil will expand quite a bit from cold to hot.   If you filled cold, then checked hot, you can be as much as a 1/4" up on the stick.

 

Jim.

pretty sure it is actually migrating as I had to add to the gear oil yestersay. I thought of the tranny vent tube possibility as well but not sure how to locate the correct one and how to check it. (Saw myself laying under the bike blowing into it...) Thanks for identifying the balancer seal Jim. Hope it's not that but if so, is it a difficult task for a non-mechanic type to handle?

pretty sure it is actually migrating as I had to add to the gear oil yestersay. I thought of the tranny vent tube possibility as well but not sure how to locate the correct one and how to check it. (Saw myself laying under the bike blowing into it...) Thanks for identifying the balancer seal Jim. Hope it's not that but if so, is it a difficult task for a non-mechanic type to handle?

 

 To locate the vent line, look from the right side, just behind the starter motor.  You'll see a tube coming off the top of the motor, which goes to a "T".  One tube will then route up towards the seat, and one down towards the shock.  This is the tranny vent.  If this line is plugged, the tranny will pressurize and possibly enough to force oil past the seal.

 

 As for the seal, it's not that difficult, but I would not say it's all that easy either.  You need to take off both right and left crankcase covers to start.   I believe you can get away without removing the clutch and starter clutch, but I don't remember off-hand.  The important thing is to get all the punch marks aligned right and you can't see them unless you get the gear off.  But if your careful, you should be able to line everything up without doing that.

 

 The nut on the end of the balancer shaft requires a special socket.  You can get it off with a screwdriver and hammer, but then you'd need to replace the nut or have the socket anyway so you can get it torqued on right.  Motion Pro sells a socket for around $9.

 

 The seal by the way is on the left hand side when you pull the shaft out.

 

 If you don't have a shop manual, I would strongly suggest getting one before you start.

 

Jim.

Edited by JimDettman

Thanks Tim. I checked the vent tube and the lower portion after the "T" was pinched between the swingarm and shock spring. Nothing was impeding the tube routed up though. I am afraid the seal may be gone but can test it with a short ride tomorrow.

 

Best,

Ron

No luck getting away with only a pinched vent tube. I took Jim's advice but searched some more on specifics. I tried the right side crankcshaft seal first. Of course I pushed the seal in beyond flush. Hope it was OK to pop it back out with a flatbalde and re-use it in the proper position. It did not look damaged and upon a 1 mile test ride no migration BUT... now I have gear oil venting into the airbox as this guy did:

 

http://www.thumpertalk.com/topic/382740-low-tranny-oil-too-full-crankcase-oil/%3Fhl%3D%252Bbalancer+%252Bshaft+%252Bseal%23entry4413389&r=

 

He says he started with the balancer shaft seal, got the airbox oil douching THEN did the right side crank seal and had success. I have the balancer seal but waiting on my new flywheel puller. In the meantime, can anyone add their experience here? Trying to picture how with a supposed proper install of the crank seal would result in what I THINK is gear oil into the airbox if the balancer seal is indeed blown. All I know to do is do the install and hope that;s it.

Edited by r_benner

No luck getting away with only a pinched vent tube. I took Jim's advice but searched some more on specifics. I tried the right side crankcshaft seal first. Of course I pushed the seal in beyond flush. Hope it was OK to pop it back out with a flatbalde and re-use it in the proper position. It did not look damaged and upon a 1 mile test ride no migration BUT... now I have gear oil venting into the airbox as this guy did:

 

http://www.thumpertalk.com/topic/382740-low-tranny-oil-too-full-crankcase-oil/%3Fhl%3D%252Bbalancer+%252Bshaft+%252Bseal%23entry4413389&r=

 

He says he started with the balancer shaft seal, got the airbox oil douching THEN did the right side crank seal and had success. I have the balancer seal but waiting on my new flywheel puller. In the meantime, can anyone add their experience here? Trying to picture how with a supposed proper install of the crank seal would result in what I THINK is gear oil into the airbox if the balancer seal is indeed blown. All I know to do is do the install and hope that;s it.

 

  There are only two seals that allow oil to migrate to/from engine/tranny; the balancer shaft seal and the right end crank seal.

 

  In general, because of the position and the way the lips are on the seals, engine oil ending up in the tranny is the right side crank, and tranny oil in the engine side is the balancer shaft seal.  Of course a badly damaged seal would let oil flow either way.

 

  I'd replace the balancer shaft seal like you plan to do, and while doing so, double check the right crank seal (you need to remove both crankcase covers to get the balancer shaft out - nuts on the right, seal is on the left side).  You should be fine as long as you were carefull prying it out and it's most likely the balancer shaft seal that's the problem.

 

Jim.

will do. wonder if I should just do the right side balancer seal while I'm in there. Is it known to rarely be the problem in your opinion? Also, still don't know understand how at first, I had the tranny/engine migration, changed the crank seal and now it shoots into the airbox. Not sure how the balancer seal would stop that but I've read it does.

 

Thanks again for your time

 

Ron

come to think of it, I don't remember a balancer seal on the right side and can't find one on the parts finder

will do. wonder if I should just do the right side balancer seal while I'm in there. Is it known to rarely be the problem in your opinion? Also, still don't know understand how at first, I had the tranny/engine migration, changed the crank seal and now it shoots into the airbox. Not sure how the balancer seal would stop that but I've read it does.

 

Thanks again for your time

 

Ron

 

 There is no right side seal for the balancer shaft.  The seal for it is on the left side.  In this diagram:

 

https://www.thumpertalk.com/shop/oem.php?partcategory=635096&manufacturer=1&category=5&year=2009&model=24544

 

 It's #26.

 

 You need to take off both right and left covers because the nut for the balancer shaft is on the right side, but it slides out on the left and the seal is on the left side.

 

<<Also, still don't know understand how at first, I had the tranny/engine migration, changed the crank seal and now it shoots into the airbox. Not sure how the balancer seal would stop that but I've read it does.>>

 

 If the balancer seal is leaking, it allows pressure from the tranny to transfer over to the engine side.   This forces a lot of air (and oil) out at the top of the valve cover into the drain tube (which is plugged) and out through the air box.

 

Jim.

Edited by JimDettman

oops, I misread your reply. you did say check the crank seal while I was in there and not balancer...

 

thanks for explaining the symptom.

 

ron

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