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Discussion Starter · #1 ·
I rebuilt my 700 Skidoo Formula III and at first was a rocket out of the shop, a tank through and it started an odd sound coming from the RAVE exhaust valves I think. Compression is rock solid at 135# accross all three cylinders, acts like one cylinder is missing? Anyone got any advice?
 

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Originally posted by Jigs
[br]I rebuilt my 700 Skidoo Formula III and at first was a rocket out of the shop, a tank through and it started an odd sound coming from the RAVE exhaust valves I think. Compression is rock solid at 135# accross all three cylinders, acts like one cylinder is missing? Anyone got any advice?
Have you had it out riding yet ?? if so is it a constant missing or low power or does it change as you speed up or slow down?..GABS
 

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have you looked at the valves? Possibly broken? I'm not too sure about RAVE, havent worked too much on the newer Doo's
 

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Discussion Starter · #5 ·
I totally rebuilt the engine, cleaned all the exhaust valves, Carbs, etc... I know that my clutch alignment is off quite a bit and might possibly be all the reason I have power loss, I put a new belt on and ran for a day or one tank of gas I should say, maybe that was enough to eat the belt to where it would not perform very well? I am just really curious what the weird noise is comming from the engine, sounds kind of hollow,like metal on plastic, hence I think it is coming from the exhaust valves. The engine does not quite want to idle right, Just wondering where to start.
 

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Did it make that noise at idle before? if it didnt then it sure wont now. If it did first take the belt off and see if the sled will idle and/or make that noise at idle. But be sure not to rev the engine past engagement RPM or you could damage your clutch without a belt in there. If the noise is gone w/o the belt, you know it has something to do with the driveline from the secondary on back. If the noise is still there, i'd start tearin into the engine lookin at the RAVE valves and see what you can find, check for sloppyness, and or broken peices, or chunks missing from the valves.
 

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Discussion Starter · #7 ·
The noise is only detectable at high RPM or when you pinch the throttle you can hear it. It is definitely coming from the engine.
 

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Just a thought, check the reed-valves too. Ya never know... it would cause a power-loss AND a strange sound. As for RAVE valves, just make sure the sliders are back in there, that's about the only thing that would cause a noticable power-loss from them. RAVE valves generally only make minor performance enhancements.
 

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Originally posted by RotaxRage
[br]Just a thought, check the reed-valves too. Ya never know... it would cause a power-loss AND a strange sound. As for RAVE valves, just make sure the sliders are back in there, that's about the only thing that would cause a noticable power-loss from them. RAVE valves generally only make minor performance enhancements.
hey, (and don't take this wrong, as I don't know everything, don't claim to, never will....) don't Ski Doos have Rotax engines in them and hence the "rotary-valve" on the intake? Or are there different ones? it's just that you suggest to check the reed-valves, I was just wondering....
 

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just another thought Jigs, when you rebuilt the engine, did you shave the heads? Did you use the same (style/type) gaskets? Increase the compression? Different gaskets under the jugs? These things may make enough difference to make the engine sound just a little different....I dunno.
 

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It's OK, you're right on twin-cylinder Rotax's, but all production triples have reed-valves.
 

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Discussion Starter · #12 ·
It is a triple rotax 700 with reed cage valves. Now that you mention the reed cages, I had to RTV the cages down as I broke off a couple of bolts and wanted to ensure a positive seal. I don't think it should be a problem but like you said, ya never know. I completely gutted the carbs and probably need to reset the needles, etc... Does anyone have the proceedure for getting all three cylinders running at the right mixture/temp?
 

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Best bet is to just get a service manual on that one, it'll say exactly where to put everything, then you can fine-tune from there. Otherwise, you may risk damage to the engine.
 

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Maybe a weak/broken Rave spring?
Just a thought.
 

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Originally posted by Jigs
[br]The noise is only detectable at high RPM or when you pinch the throttle you can hear it. It is definitely coming from the engine.
It sounds like you might have a few problems..clucth alignment for one..but the noise sounds like it might be detonation if it only comes under power...you may have a leak in a seal or to lean of mixture..but if you still tink its the valve ,here is the specs for the spring in the valve...free length 48.5mm or 1.91in. and the diamiter is .9mm or .031in. if you have them apart you might just replace them to be sure...GABS
 

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I have the service manual for the 600 and it is loaded with tons of good information. You can order it directly from SkiDoo. I think there is a link on their website for the form.

I would perform a leak test on the engine. Compression tests can come back great but you can still have a leak somewhere. The procedure is in my service manual, but I don't have it with me. This is the test that all good mechanics will do instead of a compression test.
 

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Discussion Starter · #17 ·
Haven't heard of the leak test but will ask around and see what I need to do. Started the sled last night, kicked right off, however I noticed if I messed around with the #3 cylinder throttle cable that the engine RPM's came up a little, Maybe I have some needle and seat issues?
 
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