it hasnt locked up i can still pull start it

 

Mikuni oil pumps on the 250 and 300 were almost bullet proof.350 and 400 pumps weren't mainly because they were located at the front and caught water and pumps would corrode. Only problem I ever had on the 300 were the first year 94 model 300s that used a plastic oil pump drive gear that would fail. Polaris tried to go cheap and it bit em on that one.They promptly went back to the steel drive gear that the 250 had and never really had another problem. I do agree on the injector on the carb even though many Japanese street/dirt bikes did this for years.I liked the injector at the base of the cylinder like on the 250 that mixed directly with the gas/air mixture inside the crank case rather than spray an oily gas/air mix through the carb as the 300 did. Plus many people blamed and still do blame oil pumps when they have piston problems when many times it's not the pumps fault,but the fact two strokes do require more frequent piston changes than 4 stroke pistons do that are constantly bathed in oil.Just the nature of two stroke engines.Less moving parts,but more frequent service.On the exhaust noise make sure the exhaust manifold isn't loose and leaking or the exhaust pipe hasn't popped up off the manifold because of worn/weak springs. Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse

 

I'd still do a compression check if it wont start.

 

ok thank you

 

lucky me gets to rebuild the ear on the botom of the piston broke off and there is shavings all through it

 

Piston skirt breakage is usually because of too much piston to cylinder clearance from excessive wear and not catching this in time.Trash in the bottom end isn't good.. You can try to flush it out,but always check if there is ANY up and down play on the connecting rod and crank shaft and any rough feeling crank bearings. If there is any up and down play at all,a new rod kit needs to be installed along with new crank bearings and crank seals.If you don't, it can take out a freshly bored cylinder and new piston and rings if it starts spitting lower rod bearing pieces up into the cylinder. Seen this happen a lot of times on partial rebuilds people have done.