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2001 Polaris explorer 4x4

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So few months ago I acquired a 01 Explorer 4x4 (think its a 350 but not sure) 

Anyway the owner said it started reving very high, shut the key off and still kept running 

until finally he shut off fuel and it finally died. During the run away he said the exhaust got 

red hot and has melted plastics to prove it. Said some thing flew out the tail pipe, I kinda figured

it was the top of the piston. Anyway finally got around to looking at it (have a lot of other projects in the works)

and checked the compression, Shows about 40 psi. Can hear air coming out the carb while rotating the motor over. 

Gonna pull it apart eventually, don't hear any noises or binding in the stroke, You think the piston came apart? 

any horror stories of these and is it worth my effort and money? Don't really have any money in it yet. Thoughts? Az



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Ok, so not doing anything today so figured I would look inside.

Finally get the head off and actually looks good. Was expecting an exploded

piston. Got the cylinder off and that's when I saw the damage. Hopefully it can 

be bored instead of replaced. Do you thing it was starved of 2 stroke oil? The previous owner 

had removed the carb and tried to fix it and had problems after that. I did see the oil line was connected

to the carb and the oil tank is full so I am guessing. The damage looks like it had no oil but what do I know. 

Any thoughts? Az





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Wow ! That looks bad. Nice work on the tear down. It looks like a no oil situation, have you looked to see if the oil line is obstructed or not pumping into the mixture port ? Not familiar with that bike so I’m not sure if it’s pumped. My guess is the same as yours with a no oil in the mixture.  @06kfx440 has this bike and has done some work on it. 
maybe he can shed some light on this.    

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By the sound of what you just said, no oil is bad. I always run a 32:1 mix when I get a 2 stroke initially.
But even if the oil tank was full doesn’t mean it works. The way to check that it works is to run the machine and pull off the oil injector to watch it drip oil. I’d check the crank bearings and wrist pin bearings since that heads off

I’d replace the cylinder. It’s cheaper to buy new than to hone.
If money is a factor then replace the piston.
Run your fingernail across the cylinder wall and feel if it’s gouged.

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I wouldn’t just slap a new piston in there and call it a day. How is the oil and coolant

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no coolant, air cooled unless im missing something. 

Cant seem to find a cylinder for sale, Only one I found 

was 400 plus.  The cyl wall is definitely gouged. 

The bearing looked ok but would replace if repairing. 

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Ok. Definitely air cooled. From what I see it’s a 250 or even a 300. How did the oil look. If the piston and walls look that way then there is metal in the case and you will have to split the cases to clean it out. It’s really not a big job. I had mine out and apart in a hour

Call around to bike shops and see the cost to hone and bore. Then choose the route you want to take. Used isn’t a bad idea either. But new and oem is your best bet.

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