1996 sportsman 400 (2 stroke)

Runs well, but will not idle.
When running, it blows air bakwards through the COOLING system at high volume and rate. so much so that my overflow tank is puffed up round!. If I take the radiator cap off and crank it, it blows radiator fluid to the ceiling! All this started with a stick through the radiator and a limp home with the hot light on. (< 1/2 mile). Radiator fixed, but now this.
I called a local mechanic and he thought the head gasket is blown, thus the "no idle".

2. Is this a fix I can do in my garage?? (special tools needed, etc)

Thank you!!!

BB

 

*if* its just a head gasket then yes you can do it in your garage...six bolts to take the head off and theres your gasket. you will need a torque wrench to put the head back on. but the problem is that is was ran after the hot light came on. generally these are idiot lights that give a little ledway before any real damage starts to occur. you might want to have the head checked for any warping while you have it off.... the easiest way is get a good metal ruler and put it between each of the 6 holes that the head bolts come through..should not be any gap between the ruler and where the ruler is over metal. if you dont feel like you can get a good enough evaluation of the head you can take it to any machine shop and they should be able to mic it for you.


on another note while you have the motor that far tore down have you ever replaced the piston in the machine? those stock pistons have a known reputation of "its not if they are going to bust its when" its only a few more nuts and bolts before the cylinder comes off and you can check the bore to make sure it didnt get gouged and if its all hunkydorry then pop a new wiseco piston in there....the wiseco is the only one i know of that doesnt use the same manufacturing process as the stock pistons.

 

Thank you! I pulled the gasket out and ther is a clear area where the rubber is worn off of both sides of the gasked exposing the metalic piece of the gasket. This area is dead center of one of the veins for the cooling of the block. I see no imperfections in the cyl. wall or piston. I will be ordering a wisco piston on your suggestion.

By my description, could this worn spot with no rubber on either side of the gasket be my culprit???(I hope!)

My optimistic hope is that this is all it is, as the machine runs smooth as silk, even with the compression going into the cooling system. I am convincing myself that if the block were cracked and or piston or cyl. cracked, that it would run very rough.

Thank you for your help!
BB

 

it sounds alright to me. i would still check the head for warpage..the main question is what caused the gap to let the water by the gasket allowing it to wear the rubber material off? i would definatly check the head for warping. you can get it milled down flat again if there is a problem (it will also raise the compression ratio just a tad)

 

Being new at this, I put a metal straight edge across the head at all angles and it was flat. I did the same to the cyl. between the studs and it appeared flat. Is this sufficient, or will the warp be much too microscopic to tell??
BB

 

if there was warpage then there would be a gap between the mating surfaces. better to check it and be sure than to have to do the work twice