[Fl250rider]

OK, bought a well used CRF250R a few months back, it ran good but had trouble starting, got heads done with all new parts and began starting like it should. After heads were done and installed it began blowing oil out of the trans-side case vent, (the bottom vent tube). Thought blow by was the cause so had a leak-down test done and confirmed bad rings. Ordered and installed new cylinder, piston and rings along with new clips for wrist pin. After all assembled, still leaks oil out of bottom vent. Went back over everything that could be a problem and could only come up with maybe rings are lined up with one another. Haven't been back into it to check that yet, but it is literally the last thing I can think of to be the cause of my problem. Been in and out of this motor many times to check all parts and gaskets over and over, cannot come up with a reason or solution for the oil leak. Please help and give me some ideas on what I'm missing or haven't looked into yet. I'm about to just run it til it explodes or start looking into KTM!!!

Thanks for any help you can offer fellas,
signed, a very frustrated Honda rider....

[mossman77]

Perhaps too much oil in your tranny? The oil level needs to be checked with the bike on the ground, not teetering on a bike stand. Don't simply measure and pour. Pour until oil dribbles out of the check hole with the bike held upright.

[JimDirt]

You need to check the oil level of the Engine side , if its low and the Transmission side is high , then it is most likely the Balancer Shaft Seal , if it goes bad it can cause oil to migrate from one side to the other , causing a overfill and oil to weep out the overflow tube

Part # 22 on the list (not sure of your year bike)

http://partsfinder.onlinemicrofiche.com ... A=368&B=10

[Fl250rider]

Thanks for the tips fella, I do check the oil the correct way as you have mentioned mossman. And I have heard about the oil migration problem before like you stated JimDirt. But I had seen and read where others have experienced almost the exact opposite issue I was having where trans oil migrates to engines side, suggesting bad crank seals if I understood them correctly. And my 250 is and '05, I heard a rumor that '06 seals had been modified to help cure the oil migration in caused by weaker seals in the '05s, any truth in this?

[Fl250rider]

Also I am going to order, today, new seals for crank and balance shafts, along with a few other miscellaneous things like a lot of small bolts that don't like to be torqued more than once. I found the clutch plate bolts only like to be torqued one time before the heads wring off, and the dang chain tensioner bolts are the same way, although the manual lists no torque specs for them, I just snug them up good and try not to over tighten them. Those along with the head cover bolts I get an uneasy feeling about each time I put them back on and torque them down. Thanks again for the help fellas, and any future ideas you may come across, I'd love nothing more than to be able to venture out more than just around the shop and actually get to go out and ride!

[Fl250rider]

Well, just an update, got my seals in, got em installed and ran the bike yesterday afternoon. I think I am all good to go. No leaks so far, and oil levels seem to be normal now on both sides. What a huge relief after all the work I've put into it. Wish I had come across that fix much earlier before I replaced everything but the crank, lol! Looking forward to traveling away from the homestead and ride with my brother this weekend, it's something we've been trying to do since I bought this thing 4 months ago. Cheers!

[JimDirt]

Good to hear , hopefully this solves the migration issue , it is a common issue though , which is most likely why only Honda and KTM use a seperate oil for the tranny and engine , though the engine oil stays cleaner longer , the drawback is when a seal fails , it creates a whole different set of issues

[Fl250rider]

I hope it is cured for a while, something that kinda bothers me though is the wear mark I had seen on the balance shaft, where the balance lobe is, I guess you'd call it. It seems as if it wears hard on that seal right where I guess most of the pressure is from the force of the shaft turning, and the balancer part exerting most of it's pressure on the shaft right at that point. Is that a common spot to have wear on the balance shaft? Nothing too bad I would think, just a kinda polished area I guess you could call it.

[JimDirt]

As long as you can not feel a groove with your fingers , you should be ok , its mostly the rubber , however soft , will still wear on the surface causing the shiny spot , just like water will wear holes or remove rock from constant movement , friction will cause wear no matter what the surface , but it should not be grooved , if it is , you will need to replace the shaft

[Fl250rider]

No groove or rings cut into it as far as I can tell. I couldn't feel anything when I drug my fingernail across it, just a polished looking spot like I described, so I guess I'm good to go. Just struck me as odd that's all. I'm learning a lot about these bikes as I go. Thanks for all the help so far fellas!

I also wanted to add that last Saturday I got to take the bike out to an area my brother was working in, digging a huge 20 acre pond that sits on about 150 acres. He's the super for the outfit doing the digging and clearing so we had access to the whole area. And boy did we ride! We rode for dang near 5 hours, and not so much as a hiccup from the Honda! I was stoked. Did have a small prob with rear brakes, but will have that taken care of soon. It sure was nice being able to just cruise and not be constantly worried about her leaving me stranded!

[Back2-2]

I was reading through your posts and want to offer this little bit.
- Once you eliminated the rings as a blow by potential it was pretty obvious the right side crank seal was the likely culprit. Also, anytime you have a lip seal wear line you should [ lightly] polish it with 800 -1000 grit wet paper to take that very slight ridge off. If it is large enough to catch with finger nail as you run across it then either slight adjustment to the riding area of the seal is an option or replace the shaft.
Just my 2 cents.

It sounds like you fixed her up and are good to go for now. Have fun.