2001 Polaris Sportsman 500 4x4 Fire Out Of Exhaust and Intake

[Chase Cook]

Hi I just got an Polaris sportsman 500 4x4 ATV the other day. I got it real cheap but I started to go into it because it didn't have compression so I bought a new piston and ring kit for it and installed it, but now when I try to start it all it does is shoot fire out the exhaust or the intake of the carburetor. And a timing is top dead center.;I think I can't really tell another way if it is or not. when I put it together I made sure to piston was on top and the cam lobes where facing down where are the cam sprocket is facing up. It has gas and spark. It did start a couple minutes ago but it didn't stay running and now it won't start. Do you think the valve need to be adjusted more to close better?I'm fixing to try that out and if that don't work what is the problem? Also I made sure everything was together good and right and change the oil and changed out the radiator fluid.

[Ajmboy]

Maybe one of the valves is bent?

Added more information to your topic title and moved to Polaris forum.

[Chase Cook]

The valves are fine. I think I know what the issue is now. There might be a timing mark on the crank itself to and it's not aligned with the top cam. Because I just change the teeth over a couple of times now and now it's sucking from the exhaust and shooting air from the intake. So I think it's just a timing issue now.

[Chase Cook]

Okay I just got everything back together and I made sure to crank timing in the can timing is aligned and everything else and I put everything back together like it is and I started it and it still shooting flames out the exhaust. I don't know what the problem could be at this point. The ignition timing is right.

Just now, Chase Cook said:

Okay I just got everything back together and I made sure to crank timing in the can timing is aligned and everything else and I put everything back together like it is and I started it and it still shooting flames out the exhaust. I don't know what the problem could be at this point. The ignition timing is right.

Unless the ignition timing isn't right? Its aligned with the top end.

[gillies_robert]

there is a top dead center mark, and a timing mark on flywheel, you are using correct mark? two lines match up level with head on cam gear, very simple to time. may be a sheared flyweel key?

[Chase Cook]

The flywheel key looks brand new. I just talked to someone and they said the timing is probably incorrect still. Because they said if the intake valve is open and it's making spark at the same time lol shoot out the intake/ carb and of the exhaust valves is opening at the wrong time while it's making spark it can do the same with the exhaust. So I guess I have to keep on somehow addressed in the timing for the fire right.but I looked at my owner's manual and there's two dots on the cam the line to line the cam up and and that's how I did it but it's still doing the same thing. So I guess I have to adjust one tooth out of time LOL which will take forever. But he also said that it could be a hundred eighty degrees out so I'm trying to figure out if I have to make the cam lobes facing upwards then instead of downwords then.

[MarkinAR]

Normally that symptom is caused by timing 180 degrees out. Lucky the piston hasn't smacked a valve yet. I havent timed a Polaris but on some hondas theres a couple marks then an F timing mark and a T timing mark. Pretty common to time to the wrong mark. 

[Chase Cook]

5 hours ago, Chase Cook said:

 

The timing is not a 180 degrees out. I made sure every single thing was aligned and timing was lined up right. Now it wants to suck air like it's supposed to but you and fire out the exhaust now. I mean when that happens I know it's getting gas. but I'm trying to figure out if it's something to do with the rocker arms to. Because there's one in the middle that goes into a V shape to the exhaust valve and there's two rocker arms on each side of that one that hooks up to the intake valves. Because that one that goes into a V shape, I'm trying to figure out if the valves have to be adjusted the same exact spec because they both go down at the same time. 

[fireslayer]

Lobe worn flat on the cam. these models had issues with that. New cam and lifters and start running oil with as high zinc/phosphorous content or add ZDDP additive to your oil.

[davepo]

On 3/14/2022 at 11:59 PM, fireslayer said:

Lobe worn flat on the cam. these models had issues with that. New cam and lifters and start running oil with as high zinc/phosphorous content or add ZDDP additive to your oil.

I think maybe this is what I'd check next...

[Mech]

If it's fuel injected and a twin cylinder check the injector wires aren't swapped, or the spark wiring..

[gillies_robert]

6 hours ago, davepo said:

I think maybe this is what I'd check next...

 

 

cam is probably wiped out check water pump shaft, next most common item. 

On 3/14/2022 at 10:59 PM, fireslayer said:

Lobe worn flat on the cam. these models had issues with that. New cam and lifters and start running oil with as high zinc/phosphorous content or add ZDDP additive to your oil.

Always had good luck with rotella t6 0W40, and oil changes every 50-100 hours 👍🏻