It looks to be a wiseco piston marked 536M07300 with an arrow pointing to the exhaust port side of the engine. Is this the correct installation direction?

Does anyone know if there are suppose to be two holes on the pistons skirt on the intake side?

Bruce

 

yes the arrow should be torward the exhaust side and teh piston rings should have numbers up, like dgpolaris said try to rev it in nuetral. but if it was teh limiter it wouldnt just cut out i wouldnt think i would think it would jsut not move very fast.

 

u should find out wat teh guy did before he sold it ot u. contact him find out if it was bored and a wiseco installed maybe he did something dumb like put a standard piston in a .020 bore or something.

 

Based on the number on the piston it is 0.040 over (at least the piston is).

What is still puzzling to me is the presence of the holes in the piston skirt. I know they are suppose to be present on the 400 pistons, but that is a reed valve engine. The 250 is a piston port, and from what I can see the piston should be sealing off the intake before bdc, but the way it is currently that never happens so the pressure in the case can go back out the intake (blowback, exactly what I am seeing).

At this point I am almost certain that the piston is wrong. I looked up the part numbers for both the 1992 Trail Boss, and the 2000 Trail Blazer pistons are listed as having the same part numbers, so the Trail Blazer should have the same piston as my Trail Boss, but it currently doesn't. I just need to verify if my assumptions here are correct, and then I just buy a new piston.

Thanks,
Bruce

 

The piston should have no windows in the piston at all. Sounds like the put the wrong piston in this motor. This motor is a piston port motor. Witch means that it uses the piston to seal off the intake port acting like a read valve. So if you have windows in this piston it won't run right.
AZ BAD BOYZ

 

Thank you, that is what I was thinking. I am familiar with reed induction, but I am new to piston port motors so I didn't think of this until I looked at the piston on my Trail Boss.

Now I just need to order a new piston, and get riding.

Thank you to all who have provided advice on this for me.

Bruce

 

be sure to make sure the cylinder wall is okay before u put it back together

 

technology has changed remarkably from 1992 to 2000. the piston size is not even the same. the blazer has a larger piston and shorter stroke than the boss. the blazer does have two tranfer holes in the intake side of the piston, increases intake time to engine revolution.

id be worrin about other things than looking at the sides of the piston throgh the intake, uv got bigger issues to deal with there partner

 

As said before, take the time and talk to the guy that sold you the Blazer and find out what he may have done to it. Do yourself another favor and check the compression. Check for leaks using spray around the carb, head and cylinder while it is idling assuming the compression test passed. If you do ge another piston for whatever reason, I'd take the jug to a shop and have them check it out and let them tell you what size you need to order even if it doesn't have to be bored. They won't charge you for it, so never guess.

 

I finally got it fixed.

It was the piston. It apparently was intended for use in a reed cage modified engine. I ordered a new wiseco piston (all stock polaris 250's use the same piston, I guess technology didn't advance much from 1992 to 2000), and now it runs beautifully.

Bruce