I've got nothing else I can think of if the cam is timed correct,valves adjusted,engine grounded,you have spark, and plugs have fuel and are wet other than possibly an electrical related timing issue with the ecu that controls spark timing and advancement. Worst case is to pay the 1 hour shop labor for Digital Wrench hookup to see if it can spot the problem....

 

well I Checked the compression and it only climbed to 120psi on both cylinders. I know it is supposed to be aroun 180-205...... would that keep it from firing? is the compression low because the new rings havent seated yet? I am positive the valves are adjusted right and the cam timing is correct.

 

Compression could be the problem as the 2009 manual I have shows it to show between 210-250 psi with the throttle held wide open while cranking which is quite a bit.Sounds like you need to do a leak down test as it shows 10% max allowed leakage. It would at least show you where any major leakage might be while at TDC on each cylinder bank. You can listen at the exhaust pipe for exhaust valve leakage and through the intake manifold for intake leakage from the head,plus soapy water spray around the head gasket and engine case halves to check for any leaks there along with the crank case vent for any air bypassing the rings going into the crank case and soapy water at the crank seals also. You really need a helping hand on this to keep it at tdc while checking for any leakage. Plus depending on your model (you never mentioned?? ) you either have cast iron cylinder liners or Nicasil plated cylinders. Pistons and rings must match for whichever one you have.Just trying to make sure??

 

well I checked the compression with the throttle wide open, it was at 200. I poured gas in the cylinders and turned it over and it was back firing through the air filter (Flames). that tells me its out of time? i pulled the crank position sensor and made sure there was no debris on that as well......

 

Then it's back to retracing your steps on ignition and cam timing and rechecking valve adjustment if it's backfiring.Somethings wrong somewhere.

 

well after thinking long and hard about old polaris tech's comments, I realized what the problem was while laying in bed the other night.

when I took the flywheel off the old crank I used a three jaw puller and the ring gear came off. I didnt realize it needed to be in a certain position to activate the crank position sensor so I just threw it back on ***** nilly. I jumped out of bed at 1am and took the motor out again and sure enough it was way off. I realigned it, put it back in and at 325am it came to life and purred like a kitten......

so once again the old addage...if its getting fuel, comppression and spark it has to be a timing issue somewhere.

so thanks old polaris tech for providing me the comments and direction to fix it.

however, now I have a overheating issue. the fan wasnt coming on and the check engine light came on. I unplugged the sensor per the manual started the engine and the fan came on. it has a 110 4 code (low cooolant temp voltage) any ideas??

 

Never pulled a ring gear off on the 850,whats holding it in correct position for the ring gear gap to hit the cps correctly? Can't remember if they're slots or marks for this or pressure itself holding the ring gear on the flywheel? Didn't have a chance to work on too many before I hit the door!. I do know this is one funky gear driven water pump system! If you're sure the impeller is tight along with everything else,you might try to do as we did on the rest of them and see if you can purge any trapped air that might be in the cooling system. Just jack the front end up and leave the cap off and see if it helps and the fan starts kicking on before the hot light does. Pulling the connection from the sensor will trigger the fan,so sounds like the fan's ok? If this doesn't help I'd check the resistance on the temp sensor that the manual gives..