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Discussion Starter · #1 ·
Okay I have an update, I really need help now. :bash:

Working on a 96' Fromula III 600

I checked spark on the non firing cylinder by putting a new plug in the wire and leaving the old one in while it was running, great spark. I then replaced the spark plug in the machine with the new one that was just sparking. Started the sled and still no fire on this cylinder, unless I took the sled out a ran it hard, then the cylinder kicked in, but only till back at an idle. I then pulled the wire off this plug while at idle, no difference in idle, tried the other two that where firing and witnessed a certain diff. in idle. I conlcuded the spark is there and no problems with electircal.

Second I switched carbs with on of the working cylinders (belt side cylinder is the one not firing, middle and chaincase side are working) the one I swapped it with was the middle cylinder, guess what...no change the middle cylinder still fired fine and no fire on the belt side cylinder. I am at a loss for things that could be wrong, can anyone help?? :bash:

I should also note that the when I raised the belt cover there was oily sludge on the bottom suface, inner (motor side) off the cover. Could this have anything to do with the cylider not firing? Maybe a bad crank seal or something??? There was also a light residue of gas on the floor beneath the none firing cylinder muffler outlet.

Any help or suggestions at this point would be GREATLY appreciated!!!!

Sorry for the long post just wanted to be sure I included all facts for you guys.
 

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Yes it could be a seal but you said leakage in front it may be that getting around the side. Have you taken a compresion test the pto piston may be hurt. also one of the little pea light, bore lights. helps a lot when looking down the plug hole. Good Luck Keep us posted.
 

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Discussion Starter · #3 ·
I swapped plugs from a running cylinder to the bad cylinder and no change, when I put the non running cylinder plug on one of the running cylinders that cylinder continued to fire. This tells be (I think) that the plug wire is fine.

I did another compression test last night, all three cylinders showed about 122 psi.

I also (the other day) swapped carbs, there was no change, the cylinder that was not running still did not run and the cylinder that was running continued to run fine with the carb from the non running cylinder. This tells me ( I think) that my problem does not lie with the carbs or gas delivery.

I am now leaning heavily towards the oily sludge on the bottom surface of the belt cover, I think that this oil/gas that is supposed to be in the cylinder causing fire, my problem is I cannot figure out where it is coming from?

Anyone have any ideas?
 

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joeformula3 said:
I swapped plugs from a running cylinder to the bad cylinder and no change, when I put the non running cylinder plug on one of the running cylinders that cylinder continued to fire. This tells be (I think) that the plug wire is fine.

I did another compression test last night, all three cylinders showed about 122 psi.

I also (the other day) swapped carbs, there was no change, the cylinder that was not running still did not run and the cylinder that was running continued to run fine with the carb from the non running cylinder. This tells me ( I think) that my problem does not lie with the carbs or gas delivery.

I am now leaning heavily towards the oily sludge on the bottom surface of the belt cover, I think that this oil/gas that is supposed to be in the cylinder causing fire, my problem is I cannot figure out where it is coming from?

Anyone have any ideas?
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Take a flashlight and take a look at the top of the piston. If it is white it has been running way lean and very hot. You may have damaged that piston
I just melted my mag piston from a crankcase air leak Leaned out the cylinder and melted the exhaust side of the piston down to the ring
Don't run it any more until you find the problem
The piston could start scoring the cylinder or dropping aluminum into the crank which will cost more to fix

Roadrunner1
 

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You know I am going through the exact same thing right now with a 93 Polaris Storm 750. It has spark, carbs are fine and compression is there. I have spent more hours working on this wierd problem than I can count. It is just kind of intermittant. It will drop the pto cylinder when idling, but pick it up every so often and then drop it again. I am thinking weak coils, but am extremely interested in what you find out as well. I was going to post but was worried about not getting any help.
 

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Discussion Starter · #6 ·
greezemonkey said:
You know I am going through the exact same thing right now with a 93 Polaris Storm 750. It has spark, carbs are fine and compression is there. I have spent more hours working on this wierd problem than I can count. It is just kind of intermittant. It will drop the pto cylinder when idling, but pick it up every so often and then drop it again. I am thinking weak coils, but am extremely interested in what you find out as well. I was going to post but was worried about not getting any help.
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I thinki'm getting it narrowed down, I squirted a few shots of starting fluid in the non running cylinder while the motor was running tonight, and WALA the cylinder started firing imediatly for a few seconds until the starting fluid burned off.

I am looking at a fuel deliver problem (as a few of you have already suggested). I am going to start by cleaning out the carbs, is there any magic to cleaning out the carbs? Do I need any new gaskets or a rebuilt kit before I pull them apart?

If this doesn't work I will replace the fuel pump next.

greezemonkey -
I'll keep you posted on what I find out, do the same for me if you find anything out. Have you rebuilt or cleaned your carbs yet? Change fuel pump yet? I have also been told it may be a case leak (seal), I am hoping this isn't the problem.

Thank you!!
 

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i would look at hte fuel lines to that carb. maybe its not getting fuel. you need air, fuel spark & compression to run. you tested spark, compression(kinda low). what did the plug look like when you removed it (the one from missing cylinder)?i would say its not the fuel pump because hte other cylinders are running fine, i would lean towards the carb or fuel lines for that one.
 

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have you checked your reed valves? pull them and you might find a broken petal or damaged cage. Mine was not firing on once of the cylinders at idle until you rev it up then it would be fine, then back to idle and only one cylinder again.
 

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Discussion Starter · #9 ·
Thanks for the suggestions guys.

The spark plug on the non firing cylinder is black and oily.

When I pull off the carbs I will pull the reeds out and check them as well, will it be easy to notice if something is wrong, broke or otherwise?

I'll keep updateing my results as I go so if someone else has this same problem they'll know what fixed mine.

Thanks
 

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I had this same exact problem up in Pittsburg, NH last week on my 99 mxz 600. I could not figure out what was wrong wiht it for the life of me. It was definitly only running on one cylinder, I changed the plugs, it had compression, jsut would fall on its face when I hit the gas. I was so frustrated and everyone was waiting on me, and making fun of me cuz of my sh&%box sled, so i jsut rode it. I decided to start holding it wide open whenever I could, and all of a sudden, I get a good kick of power! It was fine at WOT when it wanted to be. So I jsut kept holding it WOT whenever I could, slowly, I noticed I was getting my power back. By the next junction, I was idling fine and my sled was running like a champ. I dont know exactly what went wrong, but its running good now. Im very curious to know the answer to this problem though, because I dont want it to happen again.

Lastly, I did notice that my choke cable was stuck halfway open...when I finally fixed it, it did run better, that could have been my problem...but then the problem came back later with what seemed to be a normal choke cable.
 

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The other thing that I think helped it run normal again, was that I put dry gas in it. After I ran it with dry gas, it ran great. Just figured I'd let you guys know.
 

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My 96 FIII will only run on two cylinders until completely warmed up.I have to start it with the choke on and when it starts I immediately shut it off and let it idle by itself until temp gauge is third of the way up.You can hear the non-running cylinder pick up as it warms up and then idle perfect when warm and run great all day.If i touch the gas at all while before its warm ,I'll foul a plug immediately.Its not a fuel delivery problem or dirty carbs ,its just the way it is.I dont know if any of this will help with your sleds but its worth a shot.Good luck and let us know
 

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if you have it up and running again, squirt a little shot of starting fluid behind the clutch on the seal and look for RPM change, that oily sludge had to come from somewhere.
 

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Discussion Starter · #14 ·
Got it figured out, I tried the starting fluid trick behind the clutch and the engine reved up.

The sled is now in the shop having a new seal installed. Hope to have it back by the weekend!

Thanks for all the help guys!!
 

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Thats too bad it was a seal,but at least you found it before something bad happened.Hope you get it back soon so you can enjoy winter again
 

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how about the stator?? fires fine at higher rpm but not at idle, because of the engine speed? does that sled have a CDI box??
 
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