Cr250 oil on crank ?.

[skiboyracing]

I bought a 1999 Cr250 that had been dunked in a mud hole. Long story short he tried to start it before he drained it. Of coarse it was hydrolocked so he then drained the water out and got it to run. He road it back home and when he came back it had no compression. Well I picked it up for a few hundred bucks and tore it down last night. The top ring was toast. Very thin. Luckily the piston is in one piece and the rod is nice and tight on the up and down motion.. My question is, I notice when I roll the crank over there is oil in the bottom of the crank case that is just high enough to coat the crank as it turns. It looks like tranny oil. I don't remember this in any of my other bikes but it's been a while since I did a rebuild. Should there be oil in the bottom of the crank case that lubes the crank or should it be dry. I was thinking the lower end was all sealed bearings but I can't remember?

 

[oldfrt613]

How long do you think the bearings would last if there was no oil down there ;)

 

[skiboyracing]

haha..yeah I know. For some reason I was thinking the transmission and clutch basket were completely sealed off from the crank. It's been about 5-6 years since I've pulled one apart and couldn't remember, but then again I probably drained the oil in the past before I pulled it all apart. :laugh: Made sense there was oil there, just wasn't 100% sure. Thanks..

 

[dirt bike dave]

The crank and its bearings are lubed by oil you mix with your gas. Sometimes a little oil is unburned and it makes a small puddle in the crank case. I've never seen a bike with as much as you describe, but I guess it's possible.

If it really is tranny oil and not premix, it should not be in the crankcase.

 

[skiboyracing]

Ok that's what I was originally thinking. Perhaps this oil is really a combination of oil that was in there and water that was ingested when he fell over and sucked water into it. If that is the case then what would be a good solution to this issue. I guess I could tip the bike over and drain what I can out of it. I was thinking of sucking it up with my shop vac and a 3/8 hose attatched to it. Could I put some mineral spirits in there and rotate the crank then drain it? I don't know if that would hurt bearings. Or would it be best to simply drain it and leave it alone? I think I will also install a new right side crank seal for good measure as well.

 

[Bodge]

Can you see any debries like dirt or anything down there? It might be worth it to split the cases and be sure.

 

[skiboyracing]

No it's clean. Kinda a dark grey/brown oil mixture. There is no grittyness to it at all.. I think i'll pull the side cover off and replace the crank seal.

 

[jsned]

My buddy did the same thing to his KDX. Full of water in the crank area. He did not ride it like that though. But anyway we took the motor out (with the cylinder off) and kept flushing it out with a mix of gas and oil, mostly oil. Gas just helped thin it out to make it come out easier. Kept doing that until it came out clean.

That was 4 years ago and it runs great.

 

[flattie]

save yourself the cost of buying two new pistons and gasket sets, and tear it down completely. new crank,bearings and seals. if not you may get 20 min of riding time before you have a mess.....trust me it wont be pretty!!!!

 

[oldfrt613]

My cranks always have residual oil on it when I do a top end job. Have a leak-down test done before complete tear-down.