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Hey guys!

I am fairly new to snowmobiling and I recently got a good deal on a 1989 Yamaha Exciter 570. When I picked it up, the seller fired it up and had it running but as soon as I got it home I could only get it running while choked. The seller had mentioned that the carbs had probly needed to be cleaned, so I pulled them apart and sure enough the jets were almost completely clogged. While it was apart, I changed the fuel lines as they were old and cracked. Compression test came back good (around 120psi within 10% of each other). I got it all put back together and now I cannot get it started at all. I was careful to label everything as I took it apart and am fairly certain that I got it back together correctly.

If I pour a little premix-fuel down the cylinders the sled will fire then quickly die, leading me to believe the spark and electronics are okay. This led me to believe that I had a problem with the fuel pump, but I can see fuel in all the lines and the carb bowls were full of gas when I checked them, so is it correct to assume the pump is pushing gas into the carbs?

I did notice that the carbs were jetted with #280 main jets while the manual indicates that #340MJs should be used. If I understand correctly, the #340 jets having a bigger hole to let fuel through, would this affect the sleds ability to get started or only to continue running at higher speeds? What else inside the carbs could affect the amount of fuel getting into the engine? I had left the air/fuel mix screws alone the first time I had the carbs apart, then the second time I reset them to the manual specs, then slowly increased fuel to try to get the engine to fire.

Any ideas on things that I could try to troubleshoot this are greatly appreciated!

Thanks!
Brian
 

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I know you said you cleaned the jets but the main jets you were speaking of don,t affect anything at startup or idle.There is also a pilot jet in each carb that controls the low speed circuit.it also threads in the bottom near the main jet.Not sure if you checked it or blew out the passage that it threads into?Also make sure you run the proper jetting,even with proper jetting they were notorious for burning down or seizing.had something to do with harmonic resonance at a certain rpm where they run at.There was a couple fixes to cure the problem if I remember correctly.
 
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