2001 Z440 sno pro wont rev up when warm
ive got an 01 z440 sno pro that has been and endless battle. when i got it it was rough and beaten up, needed just about everything, and it had a issue that it would bog and die when you would try to take off after about ten minutes of riding. well i found out the crank bearings were toast when i went to replace the pto seal. so i put a 02 crank in it...brand new, with the big single pto bearing it fit just fine. i have built many engines in my life it was done meticulously. so i get it all back together and fire it up and it was starting very hard, allways started on one cyl and it would sit and struggle on one until the other would kick on and then it would run good so i cleaned the carbs again and that seemed to fix it. so all excited about riding without issue i take off to go test it in a field. it ran great for about 15 minutes then then it started doing the bog thing. it will sit and idle perfect and rev up and when the clutch engages and you try to go its like it gets a ton of fuel all at once and chokes out, if you let go of the throttle soon enough it will recover and idle. so that was last winter now here i am again trying to solve the mystery.
doing some testing lately and ive done a few more modifications. the four wire rubber connecter by the recoil seemed like it was changing the symptoms when it is plugged so i eliminated the connector and gave each wire there own separate connectors. eliminating a possible short. also where the needles in the slides sit, i found that under the c clip was a nylon washer so i put the needle in first and the washer on top of it, essentially dropping the needle setting. also i removed the guts in the air box. now the sled runs much crisper. after it is fully up to temp if you just punch it from idle on the stand it will still choke out but if you feather it it will rev up fine. is there anything i can test or look at to totally resolve this issue or is this common?its not a clutch issue im sure of that, the belt rides just a bit above the lip of the secondary. and the timing is set at like +1. ive even tried with the gas cap loose and replaced the fuel pump. all i can think of is this motor is vapor locking for some reason. please help!! its my girlfriends sled and she is just about sick of me saying i think i fixed it.