2001 Z440 sno pro wont rev up when warm - Snowmobile Forum: Your #1 Snowmobile Forum

JP250RV · 12-16-2012, 07:56 AM

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.

Rczr600rider · 12-16-2012, 08:54 AM

Check your choke cable adjustment to make sure the plungers are seating fully. There should be about 1/8" of play where the cable connects to the carb when the choke is off. Where are your air screws adjusted to? That could also be an issue. Is the elevation you're operating at different than that of the previous owner? You may need to change jets.

WardKid · 12-17-2012, 10:44 AM

Try cleaning the exhaust valves. They may be sticking or just dirty

JP250RV · 12-17-2012, 04:48 PM

the air screws are at like 1.5 out, stock jetting similar elevation, and the previous owner had the same kind of bog senario when he owned it. no exhaust valves on this engine. i will check the choke plungers that seems the most probable. when the air bog is off you can see that there is a ton of fuel fog exiting the carbs when you rev it how much should there be coming out. no drips just heavy fog. any idea about the nylon washers in the slides should they be on top of the c clip or below i saw a diagram that showed them below but it runs beter with them above

WardKid · 12-17-2012, 06:25 PM

My mistake thought I read ZR 440

**kccats** · 12-17-2012, 06:45 PM

Have you taken the shrouding off? Made sure the fan is turning?

JP250RV · 12-20-2012, 08:29 AM

i checked that the choke plungers are seating with a little slack and they are. the fan is deffinetly turning. like i said it runs fine untill its fully warmed up then it will start flooding its self. im wondering if my needles and jets are worn, increasing the size of the main. ill get a new 320 and try it or mabe a 310. so nobody knows about the plastic washer position?

**RJ Gleason** · 12-20-2012, 11:29 AM

Before changing any jets, make sure that you are not losing spark when it's warm.
The coil breaking down when warm can cause these symptoms.
Get an inline spark detector and you can then see if the spark gets weak when the engine is warmed up.

**kccats** · 12-20-2012, 04:47 PM

The plastic washer on a carb is under the needle! They are too do a half clip possition! The other plastic washer is on the throtle lever itself!

JP250RV · 12-29-2012, 04:00 PM

I was able to ride the sled today and the issue still exist. It will go for about five minutes and then it just starts running like its out of gas. I took the air box off and can see fuel fog coming out when it does it so that led me to believe the coil is bad, so i installed a know good coil from a yamaha exciter and it ran better but still started to mess up and fall on its face when you try to go. So i took the needles out and put the washer back under neath to see if it is fuel related, so its middle position with the washer under the clip. And it made the problem worse, if you pick the track up it will rev up. It doesnt make any sence. Do i need to lower the needle position? Are the nozzles worn? Im so stumped

camaro 77 · 01-02-2013, 06:44 PM

any updates on this I have a similar problem with a z440 fan

JP250RV · 01-03-2013, 06:28 AM

Im starting to notice that these sno pros have wierd issues. Good to know because i have repaired a bunch if basketcase snowmobiles and this one has me stumped. This weekend i took the stator out to test it while heating it with a hair dryer tested good. The trigger also tested good. One thing i noticed that was odd was on the flywheel on the outside there are somw whitish sweeping stains around the pickup bumps. Im wondering if the trigger is arcing after the five or so minutes. Ive seen deposits like this from bad plug wires. Theres no way to change the air gap. Before i change jetting or buy a cdi and harness does this sound like the trigger grounding to anyone? By the way what does your z do exactly