? On 2013 YZ250 2 stroke

Rowe276dad

Rowe276dad

PR Member
26 hrs on a OEM complete rebuild. Motor started making a winey/ zing noise. Had the motor split to find that the Main bearings were rusty, the crank was fine but has way to much side to side play and the Piston pin and needle bearing were gualled, like they weren't getting enough lube. To boot, the window of the piston appears to have a stress crack. We run Yamalube 32 / 1 and Bel Ray 75w. What in the hell is going on?
 
Rowe276dad said:
26 hrs on a OEM complete rebuild. Motor started making a winey/ zing noise. Had the motor split to find that the Main bearings were rusty, the crank was fine but has way to much side to side play and the Piston pin and needle bearing were gualled, like they weren't getting enough lube. To boot, the window of the piston appears to have a stress crack. We run Yamalube 32 / 1 and Bel Ray 75w. What in the hell is going on?
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I'll be curious to hear about this one… As I have the exact same bike but I have had no issues so far?
 
For a bearing to rust it must see moisture. Check the case vent hoses. Exhaust gaskets and make sure you plug the pipe before washing. For sure not a mechanic but I do know nothing rusts without moisture
 
Only thing I can think of was possibly pressure washing it with the motor still hot or again washing it then putting it away for a few weeks in freezing temperature. I guess a rule from now on, is to warm the bike back up to operating temperature after washing it.
 
The reason for a complete rebuild, was the piston window/skirt broke off and fell to the bottom. In return completely destroying everything.
 
Scott,
If you need help rebuilding it, I would recommend Parma Dave. When he does a crank he has them perfectly balanced. When I had my sons bike rebuilt, he did that and it's unbelievable how much less vibration is in that bike. Man truly takes pride in his work and we never had a problem with his engines.
 
Original44 said:
Scott,
If you need help rebuilding it, I would recommend Parma Dave. When he does a crank he has them perfectly balanced. When I had my sons bike rebuilt, he did that and it's unbelievable how much less vibration is in that bike. Man truly takes pride in his work and we never had a problem with his engines.
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Thank you for the suggestion.
 
i don't think lubrication is the issue. 32-1 that thing should be drowning in oil. I always run full synthetic oil 50-1 with zero issues. Moisture had to of gotten in through a breather bad gasket, or seal. Possibly really bad fuel.
 
Condensation from sitting in sub-freezing conditions OR unaddressed bearing wear from ingesting dirt.

Keep a good air filter and good filter oil to get max life out of the top end (original rebuild). The piston will break when too much clearance exists between piston and cylinder. Dirt will cause the piston and cylinder to wear. Excess dirt will also cause premature main bearing / con rod bearing failure.
 
Listen to the guy helping you!!! he knows what he is doing and use the parts he says, its worked for me with no issues at almost 60 hours. (knock on wood)
 
I have an 06 and I have never had an issue like that (Knock on wood). It sounds like moisture is the issue there. I'm no mechanic either but I run the same pre mix at 32-1. I do run Yamalube Trans oil plus in the case but lots of people use Rotella and don't have those issues. Sounds a little off but I have had odd things happen on my bike after using aftermarket crank kits. Crazy to hear an OEM rebuild have issues like that
 
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Maybe when the bearing was manufactured it had a tad of moisture in it. I feel like it's a freak thing. After this rebuild and all new gaskets you won't have a problem. Talkin 2 stroke not 4... They're bullet proof machines
 
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