96 600XT Top End Questions - Snowmobile Forum: Your #1 Snowmobile Forum

dpawl31 · 12-30-2012, 02:28 PM

So we swapped in the motor from the parts sled since the crank seal blew out.
Swap went without a hitch.
Until we got to the test trail, and he realized his oil tank line split, and he lost $25 worth of Amsoil all over the trailer and belly pan O_O

Went home, fixed the line, purged the air, back to trail.
About 2 hours in, he's 3/4 throttle. Starts to run like POO.

Turns out he lost 1 ring... pieces of it stuck in the spark plug, and the plug was bent up (which is why it wouldn't fire lol)

Threw a new plug it and it fired up and ran ok on the single ring. Obviously he didn't push it, but we were 3 miles out in the woods, in near blizzard visibility. Didn't want to attempt a rescue of the sled out there.
Managed to get back running just the same.

We have never done pistons/rings or pulled jugs before. He wants to sell the 2up skidoo we have to afford the repair costs, I am pretty sure we can do it ourselves. The other side of it is, the motor we swapped OUT just had a bad crank seal, but it still has 125psi in both cylinders and ran GREAT prior to blowing the seal.

I'd rather not deal with pulling pistons OUT of the jugs etc. We don't have a spring compressor and I'd like to keep them as is. So, CAN we pull the cylinder UP, an with the piston head still in the cylinder, remove the circlip and pull the wrist pin, leaving the piston in the good cylinder, then drop it right on the good bottom end?

My guess is the ring got ground up and blown right out the exhaust (aside from the bits stuck in the plug, lol) So the bottom end should be safe, yes?

Also assuming it's best to get a fresh gasket set? Those are metal gaskets right, so they are more a one-time use?

Thanks everyone, hope we can pull this off. It'd be nice to know how to do it and never worry about it. Would also be nice to save a ton of money. I've heard of guys swapping in new rings every year, so it's gotta be PRETTY easy. Considering we swapped the motor out in about an hour and a half, that's pretty cool in itself!

IRONDOG · 12-30-2012, 07:02 PM

Nobody uses a ring compressor on snowmobile engines like your Vmax- we just use our fingers. It can be done in less than 5 seconds- just squeeze the rings into the grooves with the end gaps over the locating pins and slip the cylinder over the piston. Use a little two cycle oil on the rings to help them into the cylinder. So much easier than trying to put a wrist pin clip in while holding the jug and piston in place. You need new gaskets BTW.

dpawl31 · 12-31-2012, 02:09 PM

Thanks for the reply Irondog. He went and purchased new rings, so we're pulling the pistons anyway. I told him he'd blow the motor if he reused gaskets, he got that confirmed at the dealer so he got both gaskets too. He did rent a honing tool from autozone, hopefully he knows what he's doing there as he's not waiting for me!

Any other tips besides the bolt/nut/socket trick to remove the wrist pin?

**RJ Gleason** · 12-31-2012, 04:35 PM

Put a block of wood between the piston and the the other cylinder and use a brass drift [if you have one, or a right sized socket and extension] and carefully drive the wrist pin out.
Be sure to wrap a rag around the rod, covering the base so as not to lose any parts in there.

yamadad4 · 01-01-2013, 07:59 AM

remember those cylinders are nycasil coated and you can get yourself in trouble with honing tools in the wrong hands. only takes about 15 seconds with a well oiled ball hone at slow speed in an up and down fashion.

be sure and check the end gap on the new rings and lots of 2 stroke oil on everything when re-assembling, including the bottom end.

you will be surprised at how easy this task actually is.

dpawl31 · 01-01-2013, 10:06 AM

Thanks guys!

Quote:

you will be surprised at how easy this task actually is.

You're damn right! lol

Piece of cake. I wasn't there when he drove the wrist pins out, but, it's done. lol.
Only took 3 pulls to get going, fired right up and ran great.
Kept the choke on for about 30 seconds, let it warm itself for about 2 minutes. Light drive around the backyard to get to operating temp. Let it cool for about an hour and a half.
Brought it to the trail, warmed it up, and the rode hard with varying throttle to seat the rings. I am a firm believer in the heat cycle and ride hard theory. After owning quite a few things with motors... always trying to find the best way to break a motor in, I think this is the best way. Yes, there's plenty of people that think otherwise, but I believe that to be oldschool.

The whole idea of leaving the motor running and running through a tank of gas at idle boggles my mind. No stress on the rings to seat them, and on top of that - no air or snow over the coolant to keep from overheating.
I broke my car engine in with the heat cycling/ride hard method, and I just pushed over 100k with nearly stock compression still. Pretty pumped about that.

Now that I know how damn easy this is on the 600 twin, I'll be doing my sled next!
$80 plus fluids is a fantastic deal for a new motor! ($20/set rings and $20 each gasket)

QUESTION. What do you guys expect for compression on this motor, and how long before I should test that? (will the rings be fully seated now after an hour ride, or should I wait for two more rides or so?)

FYI - the motor was 135 / 115 psi before we went out the other night. When it started running like junk, we checked at home with a hot motor - 125 / 90. Can't wait to see the new numbers!

**RJ Gleason** · 01-01-2013, 04:55 PM

140 for both would not be out of reach, but more likely 135.

dpawl31 · 01-02-2013, 12:51 PM

Good to know, because my sled is around 120 each and I've been thinking of doing the rings now since it was so easy.
We did our 2nd test ride on the new motor, thing ran mint. The temp light came on once, but - his rear flap had flipped up onto the track and was starving it of cooling snow.
So he's 2 for 2 on test rides lol. His first ride, lost the crank seal. Swapped in new motor, 2nd test ride, blown piston. Test ride 3 and 4 went flawless! lol

Probably pick up the parts for my ring job tomorrow!

yamadad4 · 01-02-2013, 08:17 PM

at 120, i would spend my money on fuel and oil. save the work for the off season.