ATV Florida Forum

94 Polaris 2 stroke . Was running fine went to start it the next day, fired right up and ran for 30 seconds sounded fine no problem then shut off and has not fired back up.  >:( I have checked the following, the plug does have a good arch, though the plug is wet after trying to start the machine but  still has a spark. I put my hand over the carb and there is suction. I put my hand over the muffler and there is blow. I put my finger over the plug hole and there is compression. New gas tried a new plug .  I even poured a little bit of gas right in the cylinder and not even a sputter. I have also dissasembled the carb and put it back together..nothing.  What in the heck happened? ??? Am I missing something >:(

compression probably too low even though you have it. would put a gage on it. then make sure your oil injection is working.. sometimes best to just bypass it and pre-mix

You finger ins't a good compression tester. You need around 100lb of compression to burn fuel. So low compression will feel OK, but it won't read good on a compression tester. Also check to see if the reeds are cracked. Look to see it exhaust smoke is coming up through the air filter. That means the reeds are bad.

dont know much(actually nothing) about 2 strokes but i do know the timing of the spark has to be right. check the spark timing. maybe a busted key or something.

The thing is is that the bike was running the entire day before this happened, no problem. The next day when we went to start it, all heck fell apart. You all have provided great ideas, would these ideas still be viable even though the bike ran fine the previous day? Compression is the only thing I think it can be, But it ran fine the previous day and it did run for about 30 seconds before it stopped. I will check compression tonight. 

How do I check the reeds?

You have to take them and inspect them for chips or cracks. The are in between the jug and the carb. Also you can try to pull it down the road with another vehicle. If the compression is border line it should start this way. Not to be a smart a$$ but that is how things break one day they work and the next day the don't.

also a good way to check the reeds is hold the block up to a light to see if the reeds are seated good..as far as running one day and not the next is that your tring to start a cold engine. you could have a scored jug and piston,broken rings,warped head..etc..thats why i bypass the oil injector and pre mix because they are unreliable and damage the engine.do you have the electric fan on it?

My wifes old polaris 400 had the same symptoms. Running fine one day and dead the next.Check the stator.If it goes bad it will not produce enough spark to run the engine. I got her a used one on ebay and it fixed the problem. You need to know if it is a six mag or not.

TRX450 it does have an electric fan. Funny you ask, the bike kept overheating, turned out the fan was not working. I traced the wires back, one wire red/white the other is brown. The terminal that the brown wire was plugged into was dead. I moved that wire to one of the terminals that one of the head lights was plugged into and the fan worked. To test the fan in this manner I had to bypass the thermal sensors in the radiator. I turned the key on and the fan turned on so I figured I fixed the fan. Then I went to start the bike and it ran 30 seconds and you know the rest of the story.

Before you all say AH Ha. As part of my troubleshooting I put everything back to how it was, still nothing.  I am leaning toward what CableGuy1 said about the stator, the spark that the plug is producing now is RED, should not it be blue or white?  Maybe running the fan was to much for the stator..hmmm

CableGuy1 how do I tell if it is a six mag or not?

Compression test showed   65...(I used a tester I use for my car)  Now what?  Rings or reeds?

65 psi is very low.. question on how you did the compression test? you mentioned that you poured gas into the saprk plug hole, I'd like to see what  the numbers are if you take a little oil like WD-40 or PB Blaster and then retest make certain that you have the throttle pin wide open during the test for accurate reading. I agree with the stator theory also.

65lbs won't burn fuel. I woild look at the reeds on the way to changing the piston and rings.

do what the one guy said and try pulling it down the road and put it in gear and see if it starts.

The bike is an automatic. Will an automatic work like a standard when pull starting. The starter works fine.

No can't pull start an auto. It's time to tear it down.

Yea, I figured.  :( Any idea how much it would cost a good shop to do a job like that? I dont want to get ripped?

Chuck I did as you suggested..a little WD-40 the compression came up to about 100..I checked the spark again, this time at night and the spark is white. Chuck, what is your thinking here? I know from cars when you do this, it confirms a ring issue.

replace the jug, piston, reeds and top end gasket set....you can buy them in a set..polaris uses the same engine in some of there snowmobiles . get on the web..there are alot of suppilers out there that just handle atv engines. i buy alot of PWC engines from sbt and have had good luck with them..PREMIX!!!!!!!

Have you tryed a new plug. I have heard on rare occasions that even though it is firing its not enough to start.

I have studied the diagrams and listened to everyones advice. I think I have two problems . Compression and a water pump seal. 60 psi of compression is too low and when it was running, coolant was coming out of the conterbalancer oil vent air tube. I would have to had taken half of the engine off to replace  the water pump gasket and check the condition of the counter balancer bearing anyway. SOOOO. this whole process looks as easy as taking off the jug and getting it bored and getting a new piston and rings and while I am spending some alone time with the bike I will take the water pump and counter balncer out to evaluate them.  The diagrams I have seen and studied, this does not look that bad of a project.  Right?
Thanks

The counter balancer is in great shape so I do not have to replace that. The compression I think may be just a bad head gasket. The bike was overheating the day before this all started. The overheating could explain run one day while the engine is hot. The next day the engine cooled down and then the head warped or even the gasket went bad. After I loosened the head bolts the head came off real easy. I am going to try a new head gasket for kicks but I realy probably change the piston anyways.

happened to me a few weeks ago, maybe your rings are stuck in, or bad. Thats what was wrong with mine