I own a 03' 300 artic cat 4x4 standard and until now the thing has run great.
There is a black cap on the engine and lately the thing has been blowing off, depending on the pressure that cap can fly a long ways. I don't know why it started doing this, its always run great.
Last week I cleaned out the carb, the air filter, changed oil + filter, and cleaned out the muffler and after that I was able to drive the wheeler in high without the cap blowing off and I took it around the roads for about 10 miles. The day after that I took it out again in low and the cap would not stay on. As soon as I got going about 20mph the thing would blow off and spray oil a good 7 feet.

Any ideas? Obviously having some sorta compression problem building up in the engine. I can say that this started when I was running the four wheeler in winter, but I have run it every winter since i've owned it. Also I rolled it last month, but I'd been having that problem before.

 

GMCnut,

I believe the part you are talking about is called a "head plug" and it is a black plug that does inthe hole between the cylinder head and the engine. It should have a little lip on it that fits into a slot. If it keeps popping out the lip may have broke off.

It sounds to me like you are getting too much pressure inside the engine block. I believe this can happen if you have too much oil, the crankcase vent tube is plugged or you are getting compression blowing by the cylinder or valve seats.

I would start by checking that you have the proper amount and type of oil in the machine. Second I would check that the crank case vent tube is not obstructed. It is the black "S" shaped tube connected between the airbox and the crankcase.

You might want to remove the tube and start the engine. At an idle nothing should be coming out that tube. If it wants to spray oil out that tube like it does the head plug then you are getting toom uch pressure in the crank case for some reason.

A compression check might then be in order and you may want to check you valve clearance.

Hope this helps SJ

 

I looked over the crank case tube and tried to clean it out. I didn't notice anything in there but I will try taking it off and idling the engine. I put in the correct amount of oil, synthectic 0W-40.

Well that'll give me a start... Thanks