If you still cant find it,it's 35,45,60. Standard 3 angle Serdi cut.

 

Ok the head work has been done. reassembled the motor, double checked the timing, still wont start. It did backfire through the exhaust .....HELP

 

Then may still be an electrical problem even if you have the mechanical part in good condition including cam timing,piston/ring clearance,valves and correct clearances. The manual has the resistance specs you can check located in the schematic diagram, plus check that you have a good fuel supply from the pump. Just pull the fuel line from the carb and crank the engine over to check.

 

I have checked the stator and the pick up coil, what other resistance is there I know I am getting fire to the plug and the plug is brand new.

 

Other resistance check is the coil and cap. Should be around .003 coil tab to ground.6300 ohms from the coil tab to the bare plug wire(cap removed) Cap should be around 5k ohms resistance.Make sure you also have a snug thumb throttle. The thumb lever should be fairly tight on these older models.1/16" to max of 1/8" on the thumb lever so the etc contacts in the throttle housing don't touch or be close enough to arc between each other.Pull the black wire from the reverse limiter module first and see if it runs ok.They can fault(most do anyway) and can cause limiting through the cdi in forward range also.Item #32.1997 Polaris SPORTSMAN 500 (W97CH50A) Electrical/Taillight | Cycle Parts Warehouse If that doesn't help,then pull the black wire from the cdi module. If none of this helps and you're getting good spark and fuel from the pump to the carb,then sounds like something in the carb. Make sure the lines from and to the fuel pump are correctly installed.

 

I know this is going to sound like a stupid question when you're checking your timing valves closed all your timing marks in line correct. I have checked everything I can check I'm getting fire I'm even spraying fuel into the carburetor it popping back through the exhaust and I still cannot get it to start. I guess my next question is could it be a hundred and eighty degrees out of time and does it spark on every revolution of the motor

 

Look at this pic from the manual and see if it helps.TDC mark on the flywheel,cam sprocket alignment pin straight up center of the head. All 4 valves should be closed and lobes pointing from the rocker arms.Valve clearance can be checked at this point.This where that manual comes in handy..

 

how can you do an accurate compression check on this motor with the automatic decompression

 

Again the manual gives you the specs on what compression should be. Average compression reading is between 50-90 psi because of the cam compression release device.