I have a Polaris trailblazer 250 that had low compression. took it to a shop to have new rings and piston put in. now I kind of have a hard time starting it. it needs a starter so I have to use the pull start. when I do get it started I have to keep my thumb on the throttle. and is kind of sluggish when I try to rev it up. and another thing it does when I ride it is after awhile it will lose all power. and to get it to go again I have to hit the throttle wide open and feather it. then after that it will drive fine for awhile then do it again. what could be the problem.

 

Make sure you only have 1/8" slack at the throttle lever or the etc switch contacts can touch and will die. Also can be a carb problem,may be running rich causing the bog,or what most people over look is crank seals leaking when they do a top end only. Any of these could be the cause.

 

thanks for the for the reply. is there a way to find out if the crank seal is leaking? and I was wondering if the carb was adjusted right. how is it suppose to be adjusted? I know where the screw is but how far out should it be adjusted?

 

Leak down test best way to check seals,gaskets for leaking,but I'd rebuild the carb first and see if that solves the problem. Air screw usually around 1 1/2-2 turns out, idle screw just adjust to where you have a slow steady idle.Carb Repair Rebuild Kit Polaris Trail Blazer Trailblazer 250 96 97 98 99 00 01 | eBay
Plus plenty of carb cleaning videos on youtube.http://www.youtube.com/watch?v=AOJlH...feature=relmfu http://www.youtube.com/watch?v=wfVQUBO7LjQ

 

ok I cleaned the carb and when I check the air screw it was only 1/4 turn out. I turned it1 1/4 out and had to turn it back in. it does rev a little better though. but I noticed that if I touched the bottom of the throttle it would idle higher.

 

Turning the air screw back in cuts the air down allowing more fuel to air ratio. When you have to do this and the air screw is less than 1 turn out,it's because it's running lean. Either the head or base gasket could be seeping or most likely the crank seals are leaking causing this.Worst one on this is the one behind the drive clutch,but I'd do both sides. Leak Down Test For 2-Stroke Engines.avi - YouTube
Plus not a bad idea to check compression even with the new top end to eliminate it as a problem. New top ends should be around 135 psi or so on average. If considerably less,may have a problem there.

 

alright. someone told me if I spray starting fluid by the crank seals I would be able to tell if they are leaking because it will idle different. is this true or not. and ill go check the compression now.

 

I checked the compression and i'm only getting 100 to 105 psi. kind of pisses me off because I had a shop redo the top end.

 

I just used old cheap wally world electrical contact cleaner as it does basically the same thing and I was a little nervous on using ether. You can spray it around the base gasket,head gasket,intake boot and case seams and you can tell if the engine rpms change along with smelling this stuff through the exhaust if it does suck into the engine. Problem on the crank seals you can't do the stator side crank for the obvious reason while it's running and on the drive clutch side you have to remove the clutch cover and the clutch to really get a good shot at this seal. When you do this you're already there.. Might as well replace the seal since you're looking at it and it just pops out and a new one tapped in place. Try around the external area first and see if could be the intake manifold or gaskets. Plus another thing is the carb itself could be the problem. When you rebuilt the top end,if the carb wasn't rebuilt,possible that it could have been the problem all along. That's a few of the reasons when I rebuilt an engine I rebuilt top and bottom both(along with new crank seals) and carb kits. I got burnt on a couple that I just did top ends that came back on me and wouldn't guarantee another partial rebuild! I just didn't like tracing down problems after I already worked on them.

 

Posted before I saw your second reply. Sounds like you need to talk to the people that did the work..