I have a 400 2stroke bored with Wiseco piston,hot seat head, 39mm carb, custom exhaust, msd total loss ignition. I'm finishing a project that my father in law built before he passed away. He was a owner and mechanic for years of a Polaris dealer in the Texas panhandle. The engine will not start seems like it has a lot of compression but I'm only able to read 70psi on the gauge you can hear ALOT of vacuum from the piston traveling up and down on the single stroke it will make cause it's so hard. With the plug out it pulls over real easy. It wasn't hard to pull when I first started messing with it and it attempted to start then got really hard to pull after. Any help would be great.

 

70 psi isn't good anyway you look at it. You can check crank seals especially the one behind the drive clutch that leaks the most with a leak down test if you wish,but still sounds like you need to pull the head off and check the piston out. Plus once you get things sorted out,bleed to the 10mm screw on top of the head to remove any trapped air pockets in the coolant. A lot of top ends have been ruined from quickly over heating,blowing head gaskets,warping heads by not doing this.

 

I've pulled the head and everything still looks new no scaring or anything. Would a ring cause this issue? Cause I know after it was rebuilt it sat for a few years

 

Yes a stuck or broken ring could have cause this if sitting over time.You could try a little oil in the cylinder and pull it over a few times,but may not help.

 

If there is a seized ring or stuck can it be reused if the engine hasn't even ran just been pulled over for testing and attempts

 

Yes it's possible but the only way to tell is to tear the top end down and check things out. If you can't save a ring,but the piston and bore are still in good shape,just order new rings,a head and base gasket.Lightly hone the cylinder if needed.

 

Ok I'll start with that when I get off work to bad you don't live near Houston lol get you to give it a quick look over. i know all the gaskets are new and piston and rings are new and bearings. And I can see the honing pattern on the cylinder wall so that should be good I hope it's a stuck ring cause not many good Polaris people down here

 

About a 4 hr drive to Houston and NO I ain't coming down.. DON'T reuse old gaskets,especially the head gasket. The squish band is already flattened from being torqued down and would leak and cause problems.Another thing I've seen people do in the past. Be sure to dribble a little two stroke oil in the lower end when you start to reassemble things.

 

I'll put alittle 2 stroke oil down in the bottom. What kind of lube or oil should I put on the wall or piston and rings when reinstalling and is there a measurement for the rings or a right wrong way to install them

 

Just a good synthetic 2 stroke oil is fine. Rings have a mark and size on the the top. Either an R or N. These marks always go up. Ring end gap between .007-.015