I inherited a couple of Trail boss wheelers about a year ago and just haven't had the time to put into them to get them going. One i got fixed easily but the other I found that the piston had blown apart. My question is after I do the rebuild with a new piston/rings, clean out the crankcase etc. Is there a test procedure for the oil injection system? I am sure I will have to break down and buy a manual but i have gotten all the torque specs from a friend. Since I cannot ask the previous owner about how it died I just want to be sure. He got it from his work when it died for parts for the other one which has almost none of the same parts. (1990 Trail Boss 2x4) Other then the tank and a couple of small things they are completely different in every place I have looked. I would like to rebuild it though as it looks like if I can get the cylinder in shape it will be a good wheeler for hunting. Also I was doing some looking at different pistons and wondered what I should be looking at. I seen several Namura top end kits for ~100 and the wiseco ones for ~150. Complete with cylinder gasket and other misc gaskets. Also on ebay seen a few polaris OEM pistons for equal price. Just wondering what brands are worth looking into. Im mostly worried about the oiler as I have no way of knowing what care was put into the thing prior to it coming apart.

 

Wiseco imo is the best after market piston around. I've used Namura with no problems also.A forged piston like Wiseco is stronger then the oem cast pistons,but a lot depends on if it's set up and broken in properly.You can destroy a good piston same as a cheaper one. The main thing on an old 2 stroke is the condition of the bottom end also. If the rod has any up and down play,it will quickly take out a new top end and there's money down the drain.I never would guarantee just a top end rebuild at our shop.

 

I figured I would check everything out once I pull the crankcase apart and put in all new seals and bearings while I had it apart. I've dealt with alot of two-strokes in the past and I know it doesn't take much to score up the cylinder beyond the point it will give compression. Thanks for the info on the pistons. I figure if it costs a couple hundred to get goin its worth the effort especially since the other only cost me a carb kit. I just haven't worked on an oil injected two-stroke which had me ever question weather the oiler was working. Only have worked on a few wheelers that weren't 4-stroke and well my previous job was working on smaller 2-strokes like saws and trimmers.

 

The 350/400 oil pump would be the more likely candidate to have problems mainly because of it's location,directly at the lower front of the atv. You can pull the 3 screws on the front plate and see if the pump wheel is turning properly and not corroded or frozen. You can disconnect the injector line on the intake manifold and see is the line is wet from oil. You can block the injector line off with just a 6mm bolt and washer in the intake manifold and premix 40-1 if the pump is trash or you don't trust it. Same thing on the 250,but you can clean the small line(or replace it) going from the pump to the base of the cylinder and while at an idle lift the pump arm all the way up. The oil should be visible pumping up the line.

 

So you dont have to have oil in the oil tank as long as its premixed? I just bought a 91 350 trail boss. Though the guy I bought it from said it was bored out to a 400.

 

Yes the oil tank can be eliminated if you premix.