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Discussion Starter · #1 ·
Hello everyone, I'm new to this forum as well as snowmobiling so please bear with me. This Christmas my uncle gave me one of his old snowmobiles a 1992 arctic cat ext with a iquid cooled 550cc engine. When he bought it the piston was burned down and he replaced it. after he rode it for awhile the piston burned down a second time. It appeared as if it had been shot right in the center. liquid aluminum was sent throught the cylinder, luckily the cylinder walls and everything were alright. so, my brother and I disassembled it and put in a new piston. we also raised the clips on the needles of the carbeurators <-(spelling??) hoping to richen it up so it would not burn down again. It has two seperate exhaust pipes that are not stock. one of which Uncle gary "modified" with part of a bimba cylinder because it was rusted through. we performed a leakdown test and everything seemed to be in order. When we first got snow here in lower WI
two days ago we took it out and ran it around our backyard a few times. and it was beautiful. lots of power and it seemed very clean. However, today we had a snowday and we took it out to the trails. It was very slow and lacked the power it had had the day before. it felt almost like it was running on one cylinder. I pulled out the plugs and one was fouled so I cleaned it off and put it back on. We started it up and it still was not running right. I rode maybe 500 yards and turned back. when I was about 100 yards from the house it popped, then shutoff, and that's all she wrote. we opened it up and the same side was burned down the same way. the other side was fine. I really would like this to go, and I don't have a job so I don't have much money. Ideally I would like to be able to fix whatever is causing this and put a new piston in. Now to my question, anybody know why this engine continues to burn up pistons? I'm not sure if I supplied you guys with all the information you need so if you want to know anything else I'll try to find out the answer for you.
Thanks in advance
Zach
 

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I am Spartacus
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It's either jetted WAY too lean or it is sucking air on that side. The most probable culprit is the rubber boot between the carb and engine. Those crack and leak, causing a lean condition.
 

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Discussion Starter · #3 ·
It has 320's in the carbs, and last time we had it out we raised the clip on the needle one space richer. so I'm thinking maybe the boot around the carb or maybe the timing is off?
 

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Discussion Starter · #6 ·
I left the snowmobile at my uncles house last week and he did a flow rate comparison of the two pipes. One was not flowing at all so he pulled off the silencer and it was completely blocked. We cleared it out and I do believe that it's fixed. We also retarded the timing a little and we will probably richen the mix on the cylinder that keeps burning up.
 

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i have had same issues with my 92 550 ext special turned out to be carb jets partialy plugged. make sure they are clean and spray some carb cleaner through it.
 
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