Snowmobile problems

[R_B]

I have a 1996 Ski Doo formula III that is not running right. It doesn't seem to have any power. It doesn't get of the line. Once you get going it starts to open up a little more. Starts right away and idles good. New needles and seats in the carbs. Different CDI box. Coils read good ohms. Reeds are good. Fuel pump looks good. Replaced fuel line in tank. Compression is 110, 110, 90. Is that the problem or is 90psi enough?

[Jeremy airjer W]

I'm sure somebody will chime in with some advice. You can also check in our snowmobile forum.

http://www.hotspotoutdoors.com/forum/ubbthreads.php/forums/52/1/Snowmobile_Users

[witgey&water]

When were the carbs cleaned last? What size are the pilot jets? The PTO and Mag carbs should be 50 and the center should be 55

[Slab_Supper]

Sounds like it might be time to put it up for sale online. Sell it for parts and save yourself the hassle.

[Bullyhead]

Change out the spark plugs or sell it to Slab online.

[R_B]

Carbs were cleaned this summer by a shop. Not sure of the size of the jet. I tried new plugs. It has been a bit of a pain in my arse. Give me a price....maybe I will sell it.

[Macgyver55]

90 psi is pretty low for a 2 stroke motor. How many miles on it?

Low compression is going to make it sluggish at best,

but may come around at higher RPMs. Sounds like a classic

low compression symptom to me.

Mine own got tough to start when it dropped below 120 psi.

With new rings its at about 150.

[R_B]

It only has 2500 miles. It starts great...just a couple pulls.

[jigginjerk]

Check your clutchs. Worn clutchs will make it doggy.

[fishingstar]

Like MacGyver said 90 psi is to low. Any thing under 110 you will start having problems. How is the belt? Have you checked the belt deflection?

Three cylinders are touchy.

Dan

[R_B]

I will look into the clutching. What exactly is "belt deflection"?

[CaptainMusky]

Belt deflection is the amount of play you have in the belt in an up and down motion between the two clutches. There shouldnt be much. Also, a worn belt makes a huge difference too. Check to see that when the machine is sitting still that the belt rides at or slightly above the top of the driven clutch (closest to the rider).

The compression doesnt sound too great, but, clutching makes a huge difference and is usually a cheap easy fix too.

Can you tell for sure that it is running on all cylinders? Once its been idling for a while, touch each cylinder with your hand to feel how warm they are.

When the carb work was done hopefully the shop synchonized the carbs properly or that will cause problems. 3 cylinders are really picky that way.

[Lip_Ripper Guy]

It's only a matter of time before that low compression becomes an issue, if it isn't already.

This sounds to me like it is clutching related, and could be any of these individually, or a combination of several:

1) Check out both clutch springs to make sure they aren't broken, or just replace them for about $15/each. With 2500 miles, they are probably soft.

2) While you are looking, check out the bushings in the clutch weights. They get a groove worn in them and have a tendency to get sticky.

3) Make sure the top of your belt is about 1/8" above the top of the driven clutch, as mentioned above. If it is lower than that, it is like your trying to take off in 4th gear in a car. If it's too high, you'll get some forward creep at idle.

4) Last but not least, take a good close look at the belt, or just replace that while you are at it.

[R_B]

It is hitting on all 3 cylinders. It wasn't at one point. Once I replaced the CDI box they all fired. I will check the clutch springs. I have another belt so I can try that.

[Lip_Ripper Guy]

Thought of something else...could be a stuck exhaust valve. Although I don't remember if that motor has RAVE.

[R_B]

I did kinda check the exhaust valves. It does have RAVE. I didn't clean them. Maybe I will look into that as well.

[R_B]

Well, I took off the secondary clutch and everything seemed OK. I changed the spring to be set at 21 lbs. I set the belt deflection as well. It didn't seem to help much. I have to give it full throttle to even get the sled to move. After about 20 yards it opens up pretty good. Any other ideas or should I go ahead and put in new pistons? Thanks for all the help guys!

[Old School]

You might have a broken motor mount. I had one that was broken and it would hardly take off but once you got it rolling it seemed fine. Took a bit to find the problem. I too would be checking the belt, carbs, jetting, clutch's, track......

Old School