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Hello, Just inherited this sled from my younger brother. He had a severe case of "tinker-itis" and messed with quite a few things under the hood. I recently got it running after he burnt up the right piston. While cleaning out the carbs I noticed that the main jet on the right cylinder (the one that blew) had a brass fitting between the jet and the carb body. Basically it spaces the main jet away from the needle about 1/8". The left carb did not have this spacer.  My Arctic Cat parts book shows the part, but calls it a jet washer. 3 Cat dealers inthe area could not tell me if both carbs should have this part or not. It would seem that this would make the thing run richer, so I'm really baffled as to why this is the cylinder that he burnt a hole in the piston. It's quite possible that he may have had the carbs swapped when it holed the piston, he can't remember and it was dis assembled when I got it.  The carb had quite a bit of greenish gunk in it and the main jet was clogged up pretty good.  

Thanks for any help!
 

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The needle doesn't go into the main jet.  If you think about it the main jet only effects 3/4 to full throttle and by that time the needle is way above the main jet.  Sooo,  the fact that the jet would be at a different distance without the spacer shouldn't be an issue.  I would think both carbs should have the spacer, but I'm not positive.
 

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yes both carbs should have the spacer
 

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Yes it should have the washer. That holds the needle jet in place. BUT, the real issue here is why did the eng. hole a piston. When I worked in Arctics warranty dept. I got all kinds of questions like this. If you can't answer the question; "why did this eng. burn down" then your repair will be based on luck. When an eng. burns down the first thing everyone dose is take the eng. apart to see what happend. That is a mistake. What should be done is to remove the eng. and have it pressure tested. Plug off the int. and exh. and pressureize the eng. to (8) psi. Because the inside of the eng. is pressureized with (8) pounds of air you can submerge it in water like you would an inner tube. Man you wouldn't belive the air bubbles. Theres more to it then this, but just a thought.

   -Auggie-

PS: "Sometimes the hard way ends up being the easy way"
 

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Hey Auggie, when did you work for Cat?  I was a Catmaster technition from 88-92, and I was in TRF in 88...maybe we've met.  I went for a dip in the hot tub at Best Western with my clothes on at some ungodly hour while I was there...you guys know how to party!

He tells us that the main jet was green and badly clogged...that is the cause more than likely.  Another possibility lies in what you said about the washer...it holds the needle jet and the main jet in place at the bottom of the main tube.  If the carb was that gummed up, he could have been pulling the needle/needle jet/main jet right up the tube and removing all the jets from the fuel in the bowl when he opens the throttle.  That side would lean out real quick in that case...  Just a thought...

Scott Nadeau
Concord, NH
 

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Discussion Starter #7
Thanks for all the tips.

Good point about the fact that the spacer would only effect idle and very low throttle oepenings.

My brother bought the sled from my mom, she probably never saw more than 1/2 throttle or speeds over 40 mph. Primarily groomed trail riding. It's possible that the gunk in the carb was causing a lean condition under higher loads. The sled had 1600 miles on it when my brother got it and he had it blown up shortly thereafter.

Is there any other way to check for crank seal problems other than pressurizing the case as one member mentioned?

I got a replacement jet spacer and will install it. My plan at this point is to put a few miles on it under medium loads and keep an eye on the plugs. Can't quite afford to drop a set of pyros in it at the moment!

One member mentioned that the jet assy might be getting pulled up out of the fuel? Is this possible? It appears that the jet assy is stationary. It's got 38mm Mikunis on it. Are there carbs where the jet moves?

Thanks again for all the help and quick response.
 

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Hi Scott,
The jet should push right up thru the tube if the washer is not on it.  The jet's outer diameter should be smaller than the tube's inner diameter.  No...by design the needle jet should not move...the washer's job is to hold it in place.

Make sure you clean everything up well before re-assembling.  No green is allowed :)  If you don't get all the parts perfectly clean, take them to a dealer and have them acid dipped for a few hours (not the floats or float caps).

Checking for seal leaks...once you get the sled to idle you can spray some carb cleaner around the seals.  If there is an air leak the carb cleaner will be sucked in to the crankcase and change the idle rpms.  Take your time with this...it is not an exact science...make sure you hit each area of each seal a few times.  Also spray around the intake boots to look for a leak there.

Good luck...let us know what you find.
Scott Nadeau
Concord, NH
 

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Scott, I worked at Arctic from 1971 to 1981 which was a little before your time. At that time it was known as Arctic Enterprise. I started working for them at the Arctic distributer know as Arctco in Fargo ND. After a couple of years they closed the Fargo dist. and they moved me to TRF. I left because they went broke in 1981.

   -Auggie-
 
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