I have been working on this since August - think i get somewhere and no

Fuel pump new, Cam shaft new, new head gasket, Rebuilt carburetor and new diagram.

Idle's great, and will hold high rpm fine. But when you crack the throttle it dies. I have played with the pilot screw, think i fix it revs up awesome 5-10 times it will rev just fine few seconds in between, let it idle for 2-3 min hit the throttle dies again, fires right back up.
Timing seems to be right on, and valves seem to be set, I will get a bad backfire if i play to much with the pilot screw but can clear most/all of that up with adjusting the pilot.

What is left for me to look at his has gone from a stupid camshaft job to a nightmare far as I'm concerned.
Could one tooth off on timing cause this or can i just not get the pilot adjusted or am i way off base, I thought the cam change would be "simple" but even with the bad cam shaft it ran better at times.

 

just a thought...maybe the float is out of wack?

 

That's what i thought, and Old Polaris tech, has helped me with that in the past, and i could be doing it 100% wrong at this point....And going to look at the carb one more time. Just seeing if there are other idea's as i have screwed with the carb over and over again checked for air leaks... Nothing has helped. If nothing else have to find someone local to look at it....preferable not the dealer......

 

One tooth off may or may not affect it,but I'd make sure the tank vent line is open,pull the fuel line to the carb and crank it over to be sure you have a steady pulse of fuel from the fuel pump. Could be the pump is weak and not able to keep up with the engine. Plus on the carb around 2.5 turns out should be sufficient on the pilot screw to eliminate it as the problem.

 

I have took the gas cap off to test that. I believe i have steady fuel (as i forgot to hook the line up and had a mess) - it is a new pump btw, but that dosn't mean much.
Is the fuel filter required to be after the pump, or can i run the filter right from the tank. I just looked and see the filter is suppose to be before the carb, not before the pump. Yes the filter is in the right direction for where i have it.
Far as the pilot screw i'm going to set that at 2.5 like you said and really check the float level again and see what happens.

 

the filter should be between the carb and pump.

 

So i played with the carb - 2 1/2 out to start with
Moved the timing up 1, RAN AWESOME, reved perfect thought it was fixed so backed the tractor out of the barn, got on the 4wheeler instantly died, fired up and same thing - horrible exhaust back fire, flames come out.

This is getting to the point of rediculas, so i then loosened the exhaust valves for the heck of it same thing.

What can cause this backfire, i have played with everything i can think of - it only happens once it warms up a little or at least ran for about 2-3 min.

 

If you've eliminated the carb or any air leak as a problem,I'd start back at the basics. Pull the flywheel and stator,check that the crank sprocket is on the tdc mark and the cam sprocket alignment pin is center of the head. Plus not that unusual for the lower sprocket slotted nut to back off causing the key to split throwing timing off also.

 

put the timing back to stock position, if it starts and idles fine (pilot jet is good) and goes WFO fine (main jet is good), its too lean on the slide needle, turn the choke on (adds more gas to cover where its missing from) some or a lot and see if that helps, if so its too lean in the mid range, check needle and see if its in the correct spot or missing any shims or spacers