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Discussion Starter · #1 ·
Hi,

New to this forum. If I make a mistake in posting this please point it out and I will try not to do it again. I just picked up a 1989 SkiDoo Formula MX sled. Got it cheap but previous owner said there was a problem with the motor.

Took off the cylinder head. Things look okay but there is some rust on the cylinder bores ... does not look too bad.

Any thoughts on cleaning up the bores and putting it back together (using new gaskets) and see if it runs. I don't have a service manual yet but will get one shortly. What are the torque for the head bolts.

I think I read some where that the oil injection pump should be blead. The oil tank still has oil in it but if I drain it to clean it do I need to bleed the pump. Any pointers on how to bleed.

If I do need new parts can anyone recommend a source for SkiDoo parts.

I'm sure I will have more questions and this forum seems to have a lot of knowledgeabe people.

Thanks;

SteveG
 

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my last sled was a 89 mx, if the cyl. are just a little rusty from sitting and not pitted get it honed out and re ring it should be fine
if the oil inthe tank lookes ok dont mess with it, those motors will
run on just about anything, NEVER had a problem with mine, ran cheap gas and oil and it ran fine. i did have better luck using champion sparkplug than ngk. if it has sat clean carbs and check fuel lines. make sure it smokes from oil when it starts if not then i would look into the injection system. had my motor out a few times for chassis work and never had to bleed injector system.
good luck and let us know how ya make out.
 

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I am Spartacus
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Also try:

Shatetree

Did you ask what kind of "motor problems" it had? MXZ800 said it right as far as what to do. There is a screw to bleed the injector system, but if you don't remove the lines, it should be OK.
 

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Discussion Starter · #5 ·
Thanks to all who replied. I should have given more details at my first post.

The previous owner told me it needed new rings. When I tried to turn it over it would not turn. When I got it home I removed the cylinder head and noticed the rust. It did not look like enough to seize the motor. I put some penetrating oil on the pistons and tapped very lightly with a piece of wood. They moved easily. I cleaned up the bores with a piece of abrasive pad, put on a little fresh oil and now it turns freely. Didn't notice any problems with the cylinder walls ... can't judge the pistons but the tops look good.

I thought I would put the head back on and give it a try. If it runs I will ride it a bit and do a compression check. If not, then I will check the compression and go from there.

I don't see any major downfall from trying to start it before going deeper into the motor ... does anyone here who knows more see one.

One other thing I noticed was after I got the motor turning over (no head installed) if I cranked it fast I would see a bit of what looked like antifreeze blowing out of the intake ports. Not a lot but enough to see it. In looking at the motor I did not see coolant connections below the head so I figured some must have gotten in when I pulled it off. I drained the coolant prior to removing the it but some remained since the motor slants forward and the coolant connections are at the higher side of the head. Does anyone see a problem with a bit of antifreeze in the mixture when I fire it up.

Even if I can't get it to run without spending a lot of money I don't have a lot to loose. I paid much less for the sled than the sales tax on a new mid level one. I could most likely part it out and make a profit.

Thanks ... I will add to this thread as I find out more. If my son had his way I would know everything by now and have it running so he could ride it.

SteveG
 

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A little coolant won't hurt it. As long as the cylinder isn't pitted you should be allright. Might want to go over it with some steel wool to make sure it's in good shape. The anti freeze may be from a blown cylinder base gasket. I've done a few of these, including my sled. You won't know that until you try to fire it up. Do a compression test to verify it's good.
 

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Discussion Starter · #7 ·
Hi,

Looks like the motor is toast. Found a bad rod. Getting the crank rebuilt looks to be too expensive but I found a similar motor on eBay. It is from a 1985 to 1987 Formula MX sled. My sled is a 1989 but the motor looks identical at least from what I can see in the picture.

Does anyone know if this motor will fit a 1989 sled.

Thanks,

Steve
 

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will fit right in, the ONLY thing you might have to change is the coolant hose routing, i have seen a couple different set-ups just depends on sled, wiring should plug right in, how much is he askin' for the motor?
 
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