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1997 Skidoo MXZ 440F
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Discussion Starter · #1 ·
I have this '97 skidoo mxz 440 fan cooled sled, it had a broken pull starter we rebuilt it and that was done. It runs like crap at first. After a little bit we mess with the wires we get it to fire on both cylinders. Boom the thing was fantastic! So fast and peppy it just wanted to go. Ran good for my dad for a night we came back the next day it was running crappy again. We replaced the wires that didn't help with our issue and we replaced the coil pack next. that made the spark a lot better but it is still weird spark ( I can't describe it very well I haven't seen it I'm always pulling over the engine) my dad describes it as a little bit erratic but it has good spark. Before we replaced anything me and my friend were going to go riding, and It ran okay and me and my friend just said screw it and rode it while it wasn't running the best ( was firing the second one every now and then as I'd get some times really good power and other times not) then it just died on me a few days later as I was riding it with only one cylinder. and it would not fire that one cylinder at all anymore. And yes we have changed the plugs (we've bought so many plugs for it.) we've drained the tank cleaned the tank filter even though it wasn't dirty just because it sat for a while and refilled it with new gas and ethanol booster. . But that one cylinder fouls spark plugs left n right and both sides have good spark with multiple different spark plugs. Someone please help! Got some decent bit of money into it and i just want to ride it next season!! sorry if the story seems a bit choppy it's been a while since we've been messing with this thing. any questions or ideas or anything are appreciated
 

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1997 Skidoo MXZ 440F
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16 Posts
Discussion Starter · #3 ·
If you switch the plug wires, does the problem follow the wire or stay on the same cylinder?
Im not sure if we have done that yet, I can check with my father> but i remember him mentioning doing it and I felt hesitant because i THought it was bad but I know its not now so well try it. But weve got new wires and a new coil so im not sure.
 

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Most two stroke engines fire both plugs at the same time, so on a two stroke, each plug fires twice per engine revolution. One spark fires the air/fuel mix, the other spark is "lost". So there is no firing order. So swapping plug wires from one to the other can help you narrow down where the problem lies. If it follows the wire, it's electrical. If it stays on the cylinder, it's probably fuel or mechanical related. It's just a tool to help you diagnose the problem and concentrate on things that are not working vs. spending time on things that may be.

Good luck!
 

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1997 Skidoo MXZ 440F
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Discussion Starter · #5 ·
Most two stroke engines fire both plugs at the same time, so on a two stroke, each plug fires twice per engine revolution. One spark fires the air/fuel mix, the other spark is "lost". So there is no firing order. So swapping plug wires from one to the other can help you narrow down where the problem lies. If it follows the wire, it's electrical. If it stays on the cylinder, it's probably fuel or mechanical related. It's just a tool to help you diagnose the problem and concentrate on things that are not working vs. spending time on things that may be.

Good luck!
we know the cylinder is getting fuel can that rule out a carb issue? I want to go there today and see if that carb might have the choke stuck or something that people are saying. Thanks!
 

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Not necessarily. Like you are checking for, you may have an enrichment plunger stuck open, the jet could have fallen out, a needle clip could have dropped off, there could be float issues, or inlet needle/seat issues. That's why you want to know if the problem follows the wire.. if it does, trouble shoot electrical. If it doesn't, trouble shoot fuel.

There could even be issues with the rotary valve (not sure if that engine has one) or even piston problems on the offending side. I'm definitely not a skidoo guy, but troubleshooting all makes should be systematic and lead you to at least narrow down the issue. That way you can concentrate on that area and not waste a ton of time and money.
 

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1997 Skidoo MXZ 440F
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16 Posts
Discussion Starter · #7 ·
Not necessarily. Like you are checking for, you may have an enrichment plunger stuck open, the jet could have fallen out, a needle clip could have dropped off, there could be float issues, or inlet needle/seat issues. That's why you want to know if the problem follows the wire.. if it does, trouble shoot electrical. If it doesn't, trouble shoot fuel.

There could even be issues with the rotary valve (not sure if that engine has one) or even piston problems on the offending side. I'm definitely not a skidoo guy, but troubleshooting all makes should be systematic and lead you to at least narrow down the issue. That way you can concentrate on that area and not waste a ton of time and money.
okay we are planning on trouble shooting as much as possible. I will let you guys know how it goes
 
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