Carb issues?

[PJtheMunchkin]

I have a 2005 Summit Rev (800) and the motor has been giving me problems and we can't figure it out.

The first burned down motor was a RKT 827 so I put the stocker back in. That burned down in about 200 yards in very deep powder on the flats. I took it to the dealer and he found a leaky crank seal and torn and leaking reed gasket. He fixed those problems, rebuilt the stock motor and sent me home with a new motor. On my second ride out in the Snowies the MAG side burned down yet again. We tore it apart and found that the Mag side piston had a melted out area in the dome of the piston, the PTO side was perfect. He did a leakdown test and all seals are tight, no leaks. The crank is fine cause the sled was running fine with no vibrations (from a tweaked crank) before the burndown. After further inspection he found that the MAG side carb main jet had fallen out. I found this highly suspicious and coincidental. I am assuming that the burned out center of the piston was caused from pre-ignition due to lack of fuel.

My question is: can the missing main jet cause a very lean condition, if in fact it was blocking the flow of fuel from the float bowl to the carb. (I was climbing a very steep hill when this happened), so maybe the fuel was sloped away from the fuel pick-up and without the main jet, it started sucking air into the MAG side carb and thus causing a burn down.

I am at a loss here and cannot afford to rebuild a 4th motor. I wanna get this right and enjoy the upcoming season.

Any ideas?

Thanks,
PJ

 

[teeroy]

that's a tough one PJ, sorry 'bout your grief. you would think it would go crazy rich with no main jet, sucking fuel up into the needle jet thru the large hole that the main screws into. unless maybe the main fell into a spot where the float got stuck so it could only fill the bowl to just below where the tube end was, causing it to suck air and fuel intermittantly. definitely a toughie to diagnose, but if nothing else was found wrong it sure seems likley, though incredibly unfortunate/unlucky.

 

[Slamnek]

I could be wrong but when a main jet falls out you would think there would be a whole pile fuel dumped into the carb causing a very rich condition so i would say you would foul plugs and flood the motor before burning it up. Check your reed boots for cracks as they are prone to delaminating. I have the same sled and found that when i was checking fuel lines and making sure bolts were tight. I had small cracks through out the boots so i replaced them with V-force reeds. You could have had a batch of bad fuel as well to cause detonation.

 

[PJtheMunchkin]

But if it was bad fuel why was the PTO side perfect? That is why I am so confused.

 

[HagmanMod1]

thats to bad about your sled , me and two of my buddies run the rkt kits and we hane lots of miles on all of them and their all still good but we also run race fuel. and when your jet falls out it would get very rich

 

[teeroy]

on a flat slide carb, does the needle jet tube just slide in and out with the main jet removed like on the old roundslide carbs? wonder if it's possible the tube was coming up with the needle and slide pulling the end of it up out of the fuel in the bowl, or bouncing up when at WOT. I'm reaching here....just can't get my head around why it would go lean if the main jet fell out.

 

[PJtheMunchkin]

I have no idea. We found no leaks, seals are good. What would cause the MAG side carb to not draw fuel while the PTO side is perfect?