The later model 400's have a line from the radiator to the carb kind of like the 650's have for this problem. The variable Venturi's can freeze up quick, I had an old Grand Marquee with one, and it sucked in the winter. It has been doing this since late summer when it was 90+ degrees outside, so I dont think its the cold. Im thinking I might still have carb vent problems, maybe some mudd has worked its way into a place I havent ventured. It will come apart after the holidays, and I do mean apart. Anybody know if there is a kit for this carb and where to look or a price? Thanks.

 

if you think it is the vent lines just remove them at the carb and test.this will help pinpoint them.it could possibly be a bad ignition coil .they will act up when they warm up and misfire

 

Hi,

May want to try this quick fix. Replace ALL your fuel lines. I had a truck that was doing close to what you are describing. I spent hundreds and hundreds of $$ at diff shops. Finally someone told me that my fuel lines had very small hairline cracks in them. When the motor warmed up it would expand the lines just a touch and it would start sucking air or leaking/losing pressure. I replaced them and it completely fixed the problem. You said its an 02 without much time so its been sitting and that is hard on any machine.

Hope it works!! and Merry Christmas.

 

ive had this problem too come to find out it was a condenser problem down by the magneto chance are it is in the electrics have the cdi and condenser and all the small and larger electronic parts tested if one or another is getting to warm then it will quit working till its cooled down then no problem it runs fine till its warm again hope this helps out