01 MC 800 BOOM! why? pictures inside.

[Sledneck26]

Rode On friday, and my bro popped the motor in his 01 MC 800 Mod. Towed it home and found this.

It was about 7 degrees Celcius i Beleive, and he was doubling his girlfriend, the sled has a extremely short snowflap, and I stole his scratchers. So he had none. Could getting hot do this? the sled has never really gotten hot, and now all of a sudden I think it did. We always ask him to put a longer snowflap on but he doesn't.

Ran it fairly easy that day. About 10 minutes into the ride i stopped in front of him, and as I started again he went to go and it bogged down and went boom.

The head is okay, and MAG piston and jug looks fine. but we havent been able to pull the cylinder off the piston yet..seems stuck

the PTO side was seized because some piston debris entered the bore and smashed over the piston siezing it at the bottom of the port on the down stroke.

The PTO piston's skirt broke right up to the wristpin, and some!

I've never seen damage like this before. and the loose pison debris took out the bottom of the case.

Sled has twin Jaws pipes and cans. I think shaved head, ported and polished he was told, Pods on carbs, Oil injection removed, if any of that makes a difference.

 

[backcountry1pr]

damn! thats burly.

 

[CATillak]

Rode On friday, and my bro popped the motor in his 01 MC 800 Mod. Towed it home and found this.

It was about 7 degrees Celcius i Beleive, and he was doubling his girlfriend, the sled has a extremely short snowflap, and I stole his scratchers. So he had none. Could getting hot do this? the sled has never really gotten hot, and now all of a sudden I think it did. We always ask him to put a longer snowflap on but he doesn't.

Ran it fairly easy that day. About 10 minutes into the ride i stopped in front of him, and as I started again he went to go and it bogged down and went boom.

The head is okay, and MAG piston and jug looks fine. but we havent been able to pull the cylinder off the piston yet..seems stuck

the PTO side was seized because some piston debris entered the bore and smashed over the piston siezing it at the bottom of the port on the down stroke.

The PTO piston's skirt broke right up to the wristpin, and some!

I've never seen damage like this before. and the loose pison debris took out the bottom of the case.

Sled has twin Jaws pipes and cans. I think shaved head, ported and polished he was told, Pods on carbs, Oil injection removed, if any of that makes a difference.

Eww pics iv seen 2 too many times myself on a big cat motor!! How many miles?

 

[WyoBoy1000]

01's had a recall on the pistons if they where not replaced that could be what happened, I had on that went with just over 2000 miles on it but I cought it soon enough it didn't harm anything. They piston was cracked all over and a little chunk had fallen of and smashed my spark plug a little causing it to run funky.

 

[tundramonkey]

I had a 01 zr800 that cat issued a recall for piston skirts cracking. Do you know if a recall was issued for the MC sleds as well? If I remember correctly the recall was in 02/03 season.

 

[Sledneck26]

Ouch, the sled was originally a drag sled for Ghostrider Motorsports in Fernie BC. Built for drag. You'd think the owner of the dealership would atleast do the recall. Its a full out Mod. So it has no Speedo or odometer, and he doesnt have a clue about the miles. The sleds been bullet proof since he bought it, until now.

Now hes in the market for a new motor. this onces pretty much garbage. part out whats left unless he gets the exact same motor.

 

[harf69]

there is a guy named mith04 i think that is selling a cat 900 bottom end with a psi 1200 on top 220hp on pump fuel check the swap meet

 

[mmsports]

Burn Down

Hard to tell from pics but from what I can see its lean was burning down snagged a port and broke piston.

 

[Sledneck26]

I thought at first he burned it down also, because it looks like the top of the piston started to melt, but then i though pieces of the skirt just hammered it down into the port. the piston wash looks good to me.

 

[CAT TRACKS]

Welcome to Arctic cat. Have had the same problem on an 02 on two different occasions. Hope Doo doesnt have the same problems as ive convinced myself to "jump Ship"

 

[CATSLEDMAN1]

red hot pistons

Looks to me like the " got hot " several times and detonated, that starts the piston fatigue cracking, hot again low speed riding in the traditional lean spot for these twins with flat slide mikuni carbs, poor old girl just fell down on its knees and quit.

REAL BAD REAL COMMON JETTING, the assumption that it didn't blow up on the bar on the hill, jetting must be ok ?.........wrong. More aluminum is destroyed by poor low to low mid range jetting than poor top end jetting. That model sled / engine / carb setup was lean out of the box in low mid range and with mods, usually unridable lean with twins. And that piston wash looks like big main jets to try and cover for lean mid range jetting, and rumbling bumbling stumbling bad sounding mid range jetting is only a sign of a bad transition not fat jetting...........and, buy an EFI.

 

[gus bohne]

I must concur,
Seen it many times, just one clip richer on the needle and it would have survived..

Problem was when you went up the one postiion it got poor mileage and loaded up some..

its not jusnk, cases are easily fixed..

 

[lynxer292b]

same thing happend to my Mountain cat 800 miles AFTER the recall! No matter what unless you put wisecos in them they are ****. Get rid of the stock pistons and put some wisecos in. My case had a hole in it too. I JB welded it back together so I could continue my trip (it actually held up for 300 miles I didnt think it would make it 3) then When I got home I tore it all down and brought it to a good welder to weld it back together. It will be ok. Or a good excuse to get a big mod motor

 

[Sledneck26]

I'd assume the crank is gabage now. allong with the topend. there has to be chips and dents in the crank after that, throwing it off balance, plus the case is full of grit and shards of aluminum, which couldnt have been good for the bearings. I dont know if i could trust a welded case either. The area around the weld weakens.

I know about the rotax midrange lean spot, and the M's one also, but not on the MC/KK motors.

Hes back this weekend and next week so we'll tear into her and clean it up.

The sled was built and raced at a lower altitude, so we assumed that the jetting should be safe at least.

 

[Killerk]

From what I have seen on these engines, the midrange is the lean spot.
Adjust needles acordingly so it is safe, then when you ride in deep pow it likes to load up... In the deep at high elevation, you are safe to drop the needles one notch, but if you leave them there for all conditions, you are lean and going to have issues.