get a stock head and mill it to 15 to 1 compression.

oh yea [img]i/expressions/face-icon-small-wink.gif[/img] datl get da job done

your runn alky so the motor shouldrun cooler anyhow

 

same prob wit our 400..all thecoolant purst outa the bottle and it overheats real fast

did everything over hte whole engine and it did it again...no signs of anything except a lil hole in the cylinder wall but rick said it suppose to be there? is this true

 

by rick i assume you mean rick ritter.. and if he said it than im sure its true

 

Mine is a compression loss problem at the head, If I torqued wrong or what ever, you can see the compression leakage marks on head, not so much on the cylinder. The head was sanded smooth and it was clean, when taken apart the three spots of black areas showing the compression leakage. The O-Rings are only damaged where the compression leaks are, the rest of the rings are new looking.

The Alcohol makes the engine run so cool it almost unreal. The exhaust temp probe is 6 inch from cylinder and it reads 600 degrees after about 10 minutes of running up the dunes, riding easy.
On the gas Polaris it reads 600-800 before you leave camp and reaches 1000 degrees in about 3 minutes and stays in the 800- 1100 mark most of time.
Bubba Bike only hit 1200 after 10 drag races up OLDSMOBILE HILL at Glamis and then drops to 100 or less 5 seconds after you let off the throttle. Its hard to adjust temp for adverse riding conditions in the dunes when using the drag bike as a play bike.

A lucky note: My 2003 400 Trailblazer, with stock piston just made its second trip of hard riding to Glamis without any problems. This Quad also pulls a 300+ pound trailmower to mow my 5 acres at home. I bought this quad new and ride the heck out of it, It was riding every day a Glamis also. I know people have troubles with the stock pistons breaking, I don't, this is my 4th 400 Polaris. 3 of which always used stock pistons, one had 5600 miles with only one piston replacement and it wasn't broken. I think the warm up is the key to long cast piston life. I am retired and ride almost daily, I have a bum right leg and used quad for tranportation all over my neighborhood.
Yes I pull traillmower with all add on's listed below, the stall clutch was a problem at first, then when you get used to it, no problem..................


good luck everyone

handycap

 

sounds like the decompression valve, you can close it off but it doesn't effect compression that much outside starting anyway.