four corner sieze

oredigger · Jan 15, 2013

My buddies stock 01' summit 800 squeaked the mag side piston again. I know this could be caused by a lot of different things, but am looking for something obvious. Still trying to figure this one out?

Only 150 miles on new top end and re-done cylinders. Died at the end of the day coming out on the road, sled was not cold. Cylinder has a crack between transfer port and exhaust port and piston sqeaked on all four corners.

Think the cylinder crack caused this or something else? He bought the sled a couple years ago and it grenaded the mag side right after he bought it. Then we rebuilt the top-end. Now this.

He runs ski doo oil and the sled did not overheat. Pilot jets were not plugged. Sled does have twin pipes on it.

summit800 · Jan 15, 2013

oredigger said:
My buddies stock 01' summit 800 squeaked the mag side piston again. I know this could be caused by a lot of different things, but am looking for something obvious. Still trying to figure this one out?

Only 150 miles on new top end and re-done cylinders. Died at the end of the day coming out on the road, sled was not cold. Cylinder has a crack between transfer port and exhaust port and piston sqeaked on all four corners.

Think the cylinder crack caused this or something else? He bought the sled a couple years ago and it grenaded the mag side right after he bought it. Then we rebuilt the top-end. Now this.

He runs ski doo oil and the sled did not overheat. Pilot jets were not plugged. Sled does have twin pipes on it.

what pipes and what was his jetting, alot of sled melt down on the way out because of lean mid range, have the crank seals ever been replaced?

oredigger · Jan 15, 2013

No, the crank seals have never been replaced. Has stock jetting, 500 mains and 17.5 pilots.

byeatts · Jan 15, 2013

oredigger said:
My buddies stock 01' summit 800 squeaked the mag side piston again. I know this could be caused by a lot of different things, but am looking for something obvious. Still trying to figure this one out?

Only 150 miles on new top end and re-done cylinders. Died at the end of the day coming out on the road, sled was not cold. Cylinder has a crack between transfer port and exhaust port and piston sqeaked on all four corners.

Think the cylinder crack caused this or something else? He bought the sled a couple years ago and it grenaded the mag side right after he bought it. Then we rebuilt the top-end. Now this.

He runs ski doo oil and the sled did not overheat. Pilot jets were not plugged. Sled does have twin pipes on it.

When Cylinders are Re Nicked they surface the top which produces a shorter cylinder and gives a tighter squish,DET. You typically need to use a thicker base gasket than stock. did you check the squish, Did you alter the head?

tukernater · Jan 15, 2013

byeatts said:
When Cylinders are Re Nicked they surface the top which produces a shorter cylinder and gives a tighter squish,DET. You typically need to use a thicker base gasket than stock. did you check the squish, Did you alter the head?

Did it have OEM piston's or aftermarket piston's

summit800 · Jan 15, 2013

oredigger said:
No, the crank seals have never been replaced. Has stock jetting, 500 mains and 17.5 pilots.

What elevation?

oredigger · Jan 15, 2013

The head is stock. Have not checked the squish.

SPI pistons, single ring.

Running 3000-6000' el

summit800 · Jan 15, 2013

oredigger said:
The head is stock. Have not checked the squish.

SPI pistons, single ring.

Running 3000-6000' el

I had cpi pipes on mine and rode the same elevation as you with stock pistons and a head I had 520 mains 20 pilots and I also think I ran a .020 shim, now I also did the piston mod on my stock pistons and then I could go to 460 mains

oredigger · Jan 15, 2013

byeatts said:
When Cylinders are Re Nicked they surface the top which produces a shorter cylinder and gives a tighter squish,DET. You typically need to use a thicker base gasket than stock. did you check the squish, Did you alter the head?

It did have 130 psi compression at 2000' after we rebuilt it the first time.

summit800 · Jan 15, 2013

oredigger said:
It did have 130 psi compression at 2000' after we rebuilt it the first time.

how mony hole base gasket is in it

oredigger · Jan 15, 2013

summit800 said:
how mony hole base gasket is in it

The base gasket doesn't have any holes in it, not sure where he got it. Mics out to about .024" which is stock.

Those pipes are crankshop twins. Once we get this figured out, I have a dynaport single that is going back on it.

03summit700 · Jan 15, 2013

Allot of people have bumped up their pilot jets to 20's. Just a thought.

summit800 · Jan 16, 2013

oredigger said:
The base gasket doesn't have any holes in it, not sure where he got it. Mics out to about .024" which is stock.

Those pipes are crankshop twins. I wonder if they needed a thicker base gasket? Once we get this figured out, I have a dynaport single that is going back on it.

Id do this on the bench, put it all back together and check squish,Id think you'd want to be no less than .061 , you might have to adjust with different base gasket. or run some race fuel in it, also If you have it on the bench,Id be doing the crank seals also

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