Back in May/June while using my ATV at work it stopped running and I diagnosed a weak spark. It would still run after a good long cool-off, well sometimes it would.
I got a CDI and it apparently fixed that issue. But a few days after that it began not starting unless full throttle was applied, at which point it would start with a small pop and run fine. Chalked that up to an obstruction in the carb as it was intermittent and started just fine for the most part and went away after a month or so. Then in October it quit running altogether. Diagnosed that to be the rectifier/regulator. Replaced it and all was well. Last week it began it's latest hair puller. It began to run rough and quickly it would not break idle without using the choke. I pulled the carb, which was amazingly clean, blew and rinsed it out, re-installed the carb and still had the same situation. But before I put the breather box back in, I tried holding the main jet needle from raising completely and it would then rev up. Kept revving it up for a little bit and now it seems to run OK(without any intervention). But low and behold it is now doing the won't start unless given full throttle thing, again intermittently. WTF? Over..........

 

im sure you have already done some of what im going to suggest, but bare with me. do u have a good strong spark if you try and start the mechine? how cold is it wher you are at? if its pretty chilly, 40 or below, it makes things hard to start. does using the choke help your problem?

if the problem is intermittent, thats usually a sign its more of an electrical problem.

 

It sounds to me that you still have some chunk of trash in the carb somewhere...

Did you remove all the jets and the idle mixture screw when you blew it out? If not, I'd try that, with a can of B12 chemtool, followed by compressed air.

 

Also make sure the idle mixture screw spring, washer and o-rong are in the passage the right way. If the o-ring and washer are flipped around, you might see an issue as you speek of. In case you did not know the order of assembly, slip the spring on the mixture screw, then the washer, next the o-ring. You need the o-ring on the idle mixture screw or the unit will not start correctly.

----- Gimpster -----

 

Well I'm back from a week long work trip and I'll try to clean the carb again.
Thanks for the suggestions, I'll post again after the cleaning.

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