2001 Trail Boss wont run when cold fuel pump test? - Polaris ATV Forum
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post #1 of 1 (permalink) Old 01-21-2014, 07:08 PM Thread Starter
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2001 Trail Boss wont run when cold fuel pump test?

Bought the machine not running. Needed battery guy said likely needed carb cleaned too. Ive cleaned what seems to be a million carbs and this one has me stumped. I have been in the carb literally 10 times in the last two days. When the machine is stone cold as in sitting overnight, it just wont fire. Shoot it with carb cleaner and it eventually will fire off.

One you get it fired the thing purrs like a kitten once warm. Will restart with a tap of the button. In fact runs perfect.

Youd think choke issue but it is physically working fine.

When it did it today i went back in the carb and there was plenty of fuel in the bowl.

On a side note in case anyone else is looking for the proper main jet size, the parts listing will say a 145 but the machine had a 120 in it. I put a 145 in it and things were no better and in fact then it was over jetted. It appears that the 120 is correct for some machines.

Plenty of spark. Tons of compression.

I also noticed that these things will not run right with the air box lid off. Ive read this and something about the 120 in some machines as well.

Ok...so fuel in the bowl, plenty of spark and compression. The three things that are required to run...and yet it wont.

So the air lid thing has me thinking. The machine seems as if it cant get a good enough draw onto the carb or something. Grasping at straws but thats my thought.

So maybe there is a vacuum leak? Intake boot is fine. The line coming off the carb going to the fuel pump appeared good at a glance but i haven't looked at it super close yet.

On to my question:

Is the fuel pump on these simply an on/off with engine vacuum turning it on? If i put a hard vacuum on it, it should hold it?

Any ideas on why this thing just cranks and cranks and cranks when stone cold?

Last edited by cerino2000; 01-21-2014 at 07:10 PM.
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