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Discussion Starter · #1 ·
When I get up above 40 I get a loud vibrating ringing that occurs that carries a high pitch. I'm wondering if the sound is normal or if something is creating friction that shouldnt be. The sled is also starting to backfire whenever I stop and if not allowed to warm up will backfire and kill. any ideas
 

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When I get up above 40 I get a loud vibrating ringing that occurs that carries a high pitch. I'm wondering if the sound is normal or if something is creating friction that shouldnt be. The sled is also starting to backfire whenever I stop and if not allowed to warm up will backfire and kill. any ideas
if you can hear a high pitched squeal and feel vibration at any speed, i would suggest closely inspecting all the bearings associated with the drive train. driveshaft bearings, jackshaft bearings, etc. i would also recommend looking at the condition of the chain and gears, as well as the chaincase oil.

as for the backfire, sounds like excess fuel. whens the last time the carbs were looked at?
 

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With a compression tester ($25 at pep boys) pull both plugs out, and screw in the tester in one. Pull at Wide Open Throttle (WOT) until the gauge stops rising. That would be your compression. Repeat for other cylinder(s). Ideal the compression should be greater than 110PSI, though, if it runs good at 100PSI it would not be a problem. You should check your compression every once in awhile, to see how the rings are seated, when the rings wear, compression drops.
 

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With a compression tester ($25 at pep boys) pull both plugs out, and screw in the tester in one. Pull at Wide Open Throttle (WOT) until the gauge stops rising. That would be your compression. Repeat for other cylinder(s). Ideal the compression should be greater than 110PSI, though, if it runs good at 100PSI it would not be a problem. You should check your compression every once in awhile, to see how the rings are seated, when the rings wear, compression drops.
Very important to note as well that your compression readings between both jugs should not differ more than 10%. Almost as important as readings over 110 lbs. I think Yamaha440 meant to include that for his explanation of "compression".
 

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Discussion Starter · #8 ·
this is my first year owning a snowmobile so when I purchased the sled I brought it in to the dealership to have it looked over. $200.00 in parts and $400.00 in labor they said everything was running properly. they replaced the bearing coming off of the driveshaft and believe all the fluids. To save money and learn my machine, I've been doing everything from here on out myself. I cleaned the carbs so I know they're good. The last time I checked compression 1 was at 110 and 2 was at 115. The backfiring I originally thought was from loading up from too many pulls. It had been -15 where I am. Yesterday it was 25 and lt started in 2 pulls like normal with no issues backfiring when I let it warm up a bit. We did a quick 30 mile run and it ran great leaving. quick response, skis off the ground. on our way back I noticed that when we came to stops the sled would backfire. Not big loud bangs, just small continuous backfires until I engaged the throttle. the ringing that I'm getting seems to be at higher rpms and its not so much a vibration that I can feel as one I can hear. The slight vibration only occurs as part of the ringing. Its a higher pitched note that carries over the engine noise. I dont seem to lose power but it has a bit of a lag and is somewhat jumpy until I increase the rpms. I nursed it back because of the backfiring so I do not know how it reacts across the powerband.
 

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My Exciter sounded like it was backbreaking. Turned out to be running on one cylinder and the "backfire" was the other cylinder popping. It was a fouled plug.
 

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Discussion Starter · #10 ·
I will check the plugs out tonight and check compression. Hopefully that'll solve the backfire problem. Maybe the ringing I'm hearing is the normal hum of the engine working at higher speeds. I dont have years of riding to be able to compare this sleds sounds to another in order to decipher what is normal. it does have a similar sound to the dust collector at work once it gets settled in at a certain rpm. I'm told its the ball bearings on the motor going bad at work. Is there some place I should check on the sled for a similar issue?
 

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Discussion Starter · #12 ·
pulled the plugs and one of them the top piece was unscrewed. Checked compression multiple times and both were at 110. put the plugs back in and fired it up and still had issues with it running rough and wanting to kill. Noticed that the exhaust port connecting to the y-pipe had a huge crack at the seam and was smoking and oozing oil. removed the exhaust and the end of the y-pipe had a puddle of oil. will be welding the exhaust this weekend. should there be that much oil?
 

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Discussion Starter · #14 ·
I had issues early in the season with the exhaust leaking so I put new springs on all around and it tightened everything up. This is an actual break in the pipe that needs to be welded as you can see through it. My concern now was the amount of oil sitting in the y-pipe and the puddle underneath from it oozing through the exhaust crack. Is that normal and if not, what might be causing that much oil to be in there and not burned off?
 
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