problem with my 86 formula mx - Snowmobile Forum: Your #1 Snowmobile Forum

jeffl9682 · 12-19-2005, 07:00 PM

I Just pulled the sled out for the new winter season. Did all the necessery things, cleaned carbs, new belt, spark plugs, new gas. Anyways i got it running. Started on the 5 pull. Not bad for a 19 year old sled. anyways. right when you start it up it idles at about 2 grand then after a couple seconds it goes up to about 4000-5000 rpm and just stays there. I have to keep my hand on the brake to prevent the track from just spinning. I checked for an airleak there the carbs conect to the rubber boot and those are fine. throttle cable is moving freely, not binding or anything. gas is on. when i take my hand off the brake the track will spin and the rpms will then continue to go up.
does anyone know where i can start to look for this problem? i have had this thing for about 10 years and it has never done this before.
im stumped.

jeff

**smallengineguy** · 12-19-2005, 07:17 PM

Is the throttle cable adjusted correctly, letting the slides drop all the way down onto the carb idle screws?

upersleder · 12-19-2005, 11:31 PM

another reason could be a crank seal gone bad.

jeffl9682 · 12-20-2005, 03:39 PM

crank seal.
my buddy told me about that. he told me a way to check it is to start the sled up and let it idle. Take some carb cleaner and spray it where the seal is and the dile should either go up or down, and if there is a difference in idle then that would tell you the crank seal is bad.
I did this and the rpms stayed the same i got no change. So i think the seal is fine. I think the throttle is fine. The cable is moving freely. It is moving the throttle on the motor up and down in its full range of motion. there is a stop where it rests against. Its hitting that. SO i believe the throttle is working properly. Also i pulled the carbs off and cleaned them both up.
Still getting the same thing.

jeff

**RJ Gleason** · 12-20-2005, 04:00 PM

Use your finger and check that the carb slides are returning completely.

It actually sounds as if you have an over running carb.
Have you checked the float level?
If one is too high, it will push too much fuel into the cyl. and cause the problem that you describe.

jeffl9682 · 12-21-2005, 05:16 PM

how do you go about checking the float level. The two black floats that are in the carbs slide on a rod connected to the bottom piece of the carb. also, the slides are the bronze colored things that run through the middle of the carb right?anyone know where i can get a diagram for this style carb online? I wish i had the repair manual for the sled.

thanks
jeff

700 Doo · 12-21-2005, 10:16 PM

Also check the rubber boots that your carbs mount into for cracks check the bottom sides real good. My old formula Z did the same thing and one of the carb boots were cracked.

jeffl9682 · 12-26-2005, 10:28 AM

just went out and checked the carb boots. no cracks in them. both look good. Still getting the same thing wheni start it up.

jeff

mx and sled 41 · 12-26-2005, 12:58 PM

check the idle screws... if your idle is too high it will also make the track move. i believe on most carbs they should be turned till snug, then backed out 1 and a half turns out