Snowmobile problem

[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?

[Ballyhoo]

That cylinder might be a little weak but I don't know if it is causing all of your problems. Have the carbs been completely cleaned? All jets, passages etc. If it idles good then gets boggy and then is good on top end it might be one jet plugged or partially plugged.

If you have a bend a light, I would look down the spark plug hole and see what the condition of the cylinder walls and top of piston are.

[R_B]

Yes, the carbs were completely cleaned. I can get an inspection light...good idea. I wouldn't say top end is good. It just picks up a bit when you get er going in a straight line.

[leech~~]

Have you checked your clutch out lately or is your belt worn. It maybe dragging down the motor?

[R_B]

The belt is good. I have not checked the clutch. I will look into that. Thanks

[ntrider]

the clutch could be dirty from years of belt dust etc. doesnt take a lot to throw off the weights, even the threads from a broken belt can get in there. a worn belt could throw off the low end however most people wont notice this because the change happens gradually. I only notice this when i put on a new belt and notice how much snappier it is on the bottom. I would start with the clutch, carbs and airbox including the rubber boots. could be sucking air if they are cracked from weathering. sometimes on mine which is a twin i will test the cylinders by removing the spark plug cap from the plug on a cylinder while it is idling and it should continue to run (very roughly). if it kills, then i will check compression or narrow it down to that one carburator not feeding the gas etc...i think 90 is getting on the low end but i think that is still enough to rule that out?

[barebackjack]

This is such a simple one but it caught me buried in a field, spark plug gap.

[R_B]

I have tried different plugs. I have yet to check the clutch and replace the belt. Thanks for all of your input!

[fishersofmen]

Compression definetely is a bit low. I have a 32 year old Enticer that has 125 in both cyl.

[ntrider]

fishersofmen,

you could be right. but i have an mxz 700 running maybe 100 in each and the thing doesnt miss a beat. i think the biggest thing to look at as far as compression would be a major difference in each cylinder such as 100 in one and 25 in the other. could a ring be stuck in the one cylinder making it lower? would it loosen after running a bit? who knows.

[fishersofmen]

Yes a major difference in compression would be an easy sign of major issues. But even the 20psi difference in the one cylinder would signify that the motor certainly isn't as healthy as it should be internally. Probly isn't causing this certain issue but should definetely be freshened up.

[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!

[leech~~]

I think you maybe in need of a new piston. Sleds use more power getting out of the hole but once up to speed don't need as much pull. I think thats why you are getting it to run a little better once it gets going. It sounds like its time my friend!

[Ice Wolf]

It is hard for any one to give you good advice with out elimination of each part of the sled. Motor, clutch, drive train, bearings, chain case and so on. You must make sure the motor is running correct before moving on to other things or you will be spending a lot of money on parts that are not the problem. I would jack up the back of the sled and remove the drive belt. Start it up and watch what RPM the primary clutch kicks in. Is it kicking in at the rite RPM? Is your motor running smooth? What is the max RPM that your sled can run at? Rev up the motor and see if you can do this with out the belt on. It should very quickly. If every thing looks good put the belt on and now see what RPM the secondary clutch kicks in. Does it do it to what the specs say it should? If so look at drive bearings, chain case, track system. By doing this you should be able to narrow it down to where the problem is.

I am not a mechanic but I do work on all of my sleds. Just giving my 2 cents. Good luck!

[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