2003 Polaris Sportsman 500 no start help

[Wilkechr]

I have a 2003 sportsman 500 ho I replaced the stator, pickup coil, ignition coil and I purchased two different CDI boxes it has fire and turns over but won't start any help would be appreciated as I am currently losing hair over this

[spock58]

Better do a compression test, it's possible that the camshaft is damaged - seen it recently on a Polaris 500 engine.

[Wilkechr]

Yeah I'm gonna do a compression test but if I was to hook a multimeter to the red 12 volt wire and ground the negative then 12 volts should come through it while turning it over correct?

[spock58]

Not too sure what you mean, it sounded like you've already confirmed that spark was tested ok?

[Wilkechr]

I didn't have a spark tester but spark appeared fine

[Curtis Underwood]

 What I do when one will not start at all is to take the air filter off and use a little starting fluid to see if it will run at all. With starting fluid it should crank and run for a few seconds if it has compression, the timing is correct and it is firing.
If it does not start this way then it is not a fuel problem because the starting fluid is easier to burn. If it does not start at all using starting fluid then you will probably need a service manual.
 You can not check the firing with a volt meter. The cdi output to the coil is to fast to read. You will just see a slight increase/decrease or jump on the meter. If you take a known good spark plug and plug plug wire to it and put the base of plug against ground(I use a ground wire and aligator clip to ground plug) then turn engine over and see a good spark then it is firing. If it is firing then I would check compression, valve settings and make sure valves are opening/closing properly and not sticking.
The timing also could be the problem, It could have jumped time.  After the machine has been run this many years the timing chain may have become worn and let it jump time. If you have a service manual it will tell you how to propery check the time. Other wise you will be trying to check time using someone elses methods and this does not always work, but if you use the method in the manual you will be assured of it being correct.

Edited April 20, 2022 by Curtis Underwood

[Wilkechr]

Alright so final update my ATV had a stuck piston ring and compression was low took it over to Power Toys Of Texas in Conroe and they fixed me up I appreciate all of y'all's help.