Start great cold but starts only on choke warm

[deerhunter]

i just picked up this 94 artic cat cougar in trade on some things the other day. it starts and runs good but when you ride it and turn it off and go to start it agian you got to choke it to get it to start and then it runs like crap for a few minute and clears up and runs great. happens everytime you start it warm. what i have done so far is cleaned carbs and put new needles and seats in. i noticed someone else before me put a fuel pump on it and its the round style while the one (exact sled) i sold a week ago was the older square style. the compression is good cold and hot. otherwise it runs great when your riding it. but wanna give it to my brother with no problems

 

[anonomoose]

This could be several things, from electrical to fuel delivery, but here is my guess.

Did you REALLY clean the carbs? I mean make sure every tiny hole got cleared, soaked in carb cleaner for a day to get the varnish out? That is on old sled and it probably has a few of those jets partially blocked and would act exactly like you describe. I would also suspect that it runs "rough for a bit" because it needs to warm up and once warm it will run anyway despite the plugged up jets.

Then I would look at the boots to be sure you don't have some air leaking in reducing the vacuum you should have. If you have cracks the machine is running too lean and which is why it needs choke even when warm. Check all lines for cracks and replace them if any even look less than perfect. Running lean is not good even if it doesn't show much sign of doing it.

Lastly I would consider weak spark... with all the things that can give you that condition. I put these in the order of probabilities.