I have a polaris 850xp,

I just finished rebuilding it and I cant get it to run. I am pretty sure the cam is timed right. I set it to to the TDC line on the front piston, and the cam sprocket is perfectly in line with the head. I am getting spark and fuel, so I am kinda baffled.

I did notice one odd thing,

according to the manual when the engine is at TDC and the cam sprocket marks are lined up the PTO cylinder exhaust valves are slightly open.

when I read through the vavle adjustment procedure it said all the rockers should have play in them when at this position the pto exhaust ones dont??

any help would be tremendously appreciated. I was up till 3AM trying to figure it out... I kept taking off the cam sprocket and rotating the engine 360 degrees to see if that would make a difference... but no luck.....

by the way the tranny is not hooked to the motor right now but I did ground the motor to the frame.

 

Did you adjust the mag side valves with the cam marks parallel to the case? Manual says then to turn the drive clutch counter clockwise 225 degrees and you will have one mark on the cam sprocket lined up with the case and another at the left top of the cam sprocket.Then adjust the pto valve clearance.

 

I will do that tonight. thanks for the tip. would that make it not run or even fire?

 

If the valve clearance and timing are not correct,then yes it would affect cranking,but wouldn't have anything to do with spark. You said in the first post that you had spark and fuel.

 

yes I am getting spark and fuel. I will make the adjustment on the valves.

as long as the TDC Mark is in position and the cam marks line up with the head correctly it doesn't matter what rotation the lower end is on does it?

last night I kept taking off the cam sprocket and rotating the engine until it came up to TDC on the next stroke then reattaching the cam sprocket to see if there was a certain revolution that it had to be on at TDC to make it work......

but according to the manual it doesnt matter.... as long as the TDC Mark is where its supposed to be and the cam marks are lined up with the head it should work right??

 

You shouldn't have to keep taking the cam sprocket off. Once you establish tdc on the crank for the mag side piston,align the cam and sprocket with both marks parallel to the case and adjust the mag side valves.Then rotate the engine by the clutch clockwise until the pto mark comes up. As far as which way you turn the crank,it shouldn't matter,BUT we went by the book on valve adjustment.

 

ok, I will get it straight as soon as i get home from work, hopefully adjusting the valves correctly will do the trick....

 

well I got the valves adjusted, still no luck. I took the motor back out of the quad to ensure the flywheel key wasnt sheared. double checked and made damn sure the cam was timed correctly per the manual. got it back in and nothing.

I checked the spark and it was white. I tried a brand new plug and it was bright blue.(wasnt the right plug so I couldnt put it in the motor).........it did manage one backfire that was it.....

the plugs were wet as well this time. I cant figure out what I am missing I dont have the transmission bolted in right now but its sitting in the frame with all the electrical plugs plugged in. I grounded the motor to the frame and it isnt throwing any DTC codes....... I dont have any coolant in it right now would that make a difference? does it need the gas cap to pressurize the system?


im baffled...it ran fine when I took it apart. (except for the loud knocking sound) I just put a new crank, rods piston and rings in it.....

 

bump....Im stumped can anyone offer any more suggestion??

 

morning bump...