Crank Seals are shot, have a few questions

[ChowellYZ146]

Went to replace the clutch cable on my 09 YZ 250 this last weekend, and found oil in side of the left side housing. Pulled the fly wheel and determined the seal was shot. Drained the oil and started think about how much oil this bike has been puking out of the power valve this summer and started wondering if the clutch side seal was also shot. It doesn't smoke excessively or smell weird, but the amount of oil that comes out of it has always been a thing of mystery. I had rejetted it and cleaned the carb, adjusted the float all that fun stuff. I measured the oil that came out of the case tonight and it's about 3 ounces short, which tells me it's sucking in oil from the transmission. New seals are on the way and I've read that I can replace those without splitting the case. 

My concern is, and I'm hoping some of you have had experience with this, are my seals shot because of bad bearings? Or could they just have worn out and need to be replaced. 

I also ordered a top end gasket kit and figured I would pull the jug off this weekend and see if there is any play in the rod. I'm worried because I'm leaving for Moab next Friday to go ride and it's super cold in Utah right now. Don't really want to be in my cold ass garage replacing these things, but I want to take this bike with me. I have a back up bike, but would rather take the 250. 

If there isn't any play in the rod and the crank bearings feel good, should I not worry?

Thanks in advance for the input!

[Kinger317]

You're right, most of the time a bad bearing will eat seals. In my experience with these engines that's not the rule. I have worn out seals and the bearings were fine. check them out when you get into it, there either good or they're not but the condition of the seal does not necessarily tell you how the bearing is. Changing them is not a big deal, engine stays in the bike.

Edit: if their original it may be time

[Smoking 2's]

8 hours ago, ChowellYZ146 said:

Went to replace the clutch cable on my 09 YZ 250 this last weekend, and found oil in side of the left side housing. Pulled the fly wheel and determined the seal was shot. Drained the oil and started think about how much oil this bike has been puking out of the power valve this summer and started wondering if the clutch side seal was also shot. It doesn't smoke excessively or smell weird, but the amount of oil that comes out of it has always been a thing of mystery. I had rejetted it and cleaned the carb, adjusted the float all that fun stuff. I measured the oil that came out of the case tonight and it's about 3 ounces short, which tells me it's sucking in oil from the transmission. New seals are on the way and I've read that I can replace those without splitting the case. 

My concern is, and I'm hoping some of you have had experience with this, are my seals shot because of bad bearings? Or could they just have worn out and need to be replaced. 

I also ordered a top end gasket kit and figured I would pull the jug off this weekend and see if there is any play in the rod. I'm worried because I'm leaving for Moab next Friday to go ride and it's super cold in Utah right now. Don't really want to be in my cold ass garage replacing these things, but I want to take this bike with me. I have a back up bike, but would rather take the 250. 

If there isn't any play in the rod and the crank bearings feel good, should I not worry?

Thanks in advance for the input!

My guess is the seal behind flywheel cover on the clutch shaft is leaking not the Crank seals. #26 on diagram.

You can fire it up and spray a little starting fluid or similar around the Crank seal and if the rpms don't change your fine

Yes Crank seals can be replaced without splitting cases if it comes to that

[rpt50]

There should zero up-and-down play in the flywheel.  If you feel anything at all, time for new bearings.  Same for the rod (no up and down play) when you pull the top-end.

Oil in the left side would probably not be from the crank seal.  Remember that on a two stroke the crank is lubricated by premix, and the oil for the transmission is separate.   Not sure with the YZ 250 exactly what the set up is, but some bikes have a seal around the clutch mechanism concealed behind the left side case.  That is where the oil is likely coming from.  

Edit: Sorry, but I did not fully read the post just above mine.  Yes, part #26 is likely the problem.

Edited December 13, 2018 by rpt50

[ChowellYZ146]

5 hours ago, rpt50 said:

There should zero up-and-down play in the flywheel.  If you feel anything at all, time for new bearings.  Same for the rod (no up and down play) when you pull the top-end.

Oil in the left side would probably not be from the crank seal.  Remember that on a two stroke the crank is lubricated by premix, and the oil for the transmission is separate.   Not sure with the YZ 250 exactly what the set up is, but some bikes have a seal around the clutch mechanism concealed behind the left side case.  That is where the oil is likely coming from.  

Edit: Sorry, but I did not fully read the post just above mine.  Yes, part #26 is likely the problem.

The oil on the left side I'm 99% was premix and gas. As for movement with the fly wheel, there was none. I think the oil coming from the exhaust port is definitely transmission oil though, it has a consistency that isn't burnt premix. 

10 hours ago, Kinger317 said:

You're right, most of the time a bad bearing will eat seals. In my experience with these engines that's not the rule. I have worn out seals and the bearings were fine. check them out when you get into it, there either good or they're not but the condition of the seal does not necessarily tell you how the bearing is. Changing them is not a big deal, engine stays in the bike.

Edit: if their original it may be time

Thanks for a little reassurance! I'll be tearing off the top end on Saturday and going from there. Fingers crossed there isn't any play in the rod. 

[YZDOC]

Replace all seals and be sure for your trip. Easy to do job with engine in the bike. Only pisser is the one on the jug for the PV shaft.

Excessive spooge out the PV vent can be a tired top end. 

[ChowellYZ146]

21 hours ago, 2 STROKE YZ DOC said:

Replace all seals and be sure for your trip. Easy to do job with engine in the bike. Only pisser is the one on the jug for the PV shaft.

Excessive spooge out the PV vent can be a tired top end. 

It's actually coming out of the exhaust port on the cylinder. And it's not entirely burnt premix. The top end was just done 33 hours ago, I tried to take it off to check the crank last night and the dumbass guy I bought it from decided that all gaskets needed to have a sealant on each side of the gasket. So basically the jug is glued to the case and I'm struggling to get it off. The joys of buying used bikes!

Edited December 14, 2018 by ChowellYZ146
Wording

[YZDOC]

15 minutes ago, ChowellYZ146 said:

It's actually coming out of the exhaust port on the cylinder. And it's not entirely burnt premix. The top end was just done 33 hours ago, I tried to take it off to check the crank last night and the dumbass guy I bought it from decided that all gaskets needed to have a sealant on each side of the gasket. So basically the jug is glued to the case and I'm struggling to get it off. The joys of buying used bikes!

"the dumbass guy" A person whom thinks they are mechanically inclined and should stick to easier task such as yard work. 

"all gaskets needed to have a sealant on each side" A sign that the person whom should stick to yard work, didn't replace the gaskets with new ones, but bought a $3 tube of gasket sealer at the walmart auto section.

"The joys of buying used bikes!" I look over bikes with a fine tooth comb and come up with a price in my head of what things cost to make them right. This is most of the time fasteners. Found many wrong things internally over the years also. Always a crap shoot. 

Hope you get it sorted for your trip. 

[ChowellYZ146]

Finally got the jug off and found all sorts of surprises! The up side is the crank seems solid. The head.... not so much. Luckily this wasn’t caused anytime since I’ve had the bike. What are your thoughts on the head? I have a few friends who say screw it, and run it the way it is.

[YZDOC]

1 hour ago, ChowellYZ146 said:

Finally got the jug off and found all sorts of surprises! The up side is the crank seems solid. The head.... not so much. Luckily this wasn’t caused anytime since I’ve had the bike. What are your thoughts on the head? I have a few friends who say screw it, and run it the way it is.

That head is pretty stuffed but it can be ran. That is what happens when the big end bearing goes out at high RPM and the engine is ran. I'm sure the jug took a beating at the same time that happened to the PO. 

I would clean it up real good and make sure there are ZERO particles that are embedded that can flake off. It can be turned and the volume re-applied at a machine shop. Recommend doing that next time around if you are in a pinch to get it together now for a trip/ 

[Kinger317]

Good news on the crank[emoji106] Man that head is ugly! I'm sure it's fine to run, but when you get the chance re-turn that one or a new one from Yamaha is only $100 (x model) YZ is a little more for some reason.

[ChowellYZ146]

Thanks for everyone’s input! I think I’ve finally reached my annoyance point and decided to just shove it to the side of the garage until I have more time. I have a trusty little 125 that I’ll take on my trip with me.

I think

[Kinger317]

Ha ha, take the 250!

[ChowellYZ146]

On 12/14/2018 at 8:59 PM, Kinger317 said:

Ha ha, take the 250!

Lol, honestly I've desert raced and rode some gnarly stuff on my YZ125, it's so much fun. I'm not at all disappointed that I'm not taking the 250. And I realized when I got my top end gasket kit, that I accidentally ordered it for the 125. ?At least I'll have a project to work on this winter, the 250 needs more love than I expected.