QuestionI HAVE A 97 POLARIS 400 SPORTSMAN 4X4 I HAVE CLEANED THE CARB. 3 TIMES VERY THROUGHLY AND IT WILL NOT STAY IDLE. AS LONG AS YOU KEEP IT REV UP IT WILL STAY CRANKED. WHEN U LET GO OF THE THROTTLE IT DIES. IT IS A TWO CYCLE ALSO. THE ATV WAS GIVEN TO ME BY A FRIEND AND HE SAYS HE HAD THE SAME PROBLEM WHEN HE BOUGHT IT BRAND NEW. I AM I THOUGHT A FAIR MACHANIC BUT THIS ONE HAS BEAT ME,
AnswerHi Phil:
First let me start off by saying I am a lawn and garden guru. I have always been a believer that if it mows or blows (Grass and Snow that is) people are happy, if its something someone rides it may never work to a customers satisfaction.
I have never worked on ATV's.
That being said this is a basic theory question and I will give you a couple places to start looking.
Carburetion: Since the unit did this since new its possible that it has a defective carburetor. I am sure that the carb has both an idle circuit and a high speed circuit similar to an air cooled mini bike engine. If you have taken the carb apart and cleaned it with a good carb cleaner and probed ALL the passages with a fine wire then i would try a different carburetor. This is one area to look.
Another area i would be looking is to pressurize the engine and look for air leaks. An air leak in a two cycle engine will drive you crazy. Without the proper tools, ie block off plates, service manual, etc, it may be hard to do this test. These are the areas I would be looking.
I can not tell you exactly how to perform the pressure test as i indicated earlier as i have never worked on an ATV, but if you have a leaky gasket or seal a pressure test will indicate this immediately.
I just want to clarify that a 2 cycle pressure test is NOT a compression test or a cylinder leak down test. It is a test that is performed by blocking off the intake, exhaust, and pumping low pressure air into the inside of the engine. The air pressure is then monitored for a period of time to determine leakage.
