I can now start my 1999 Polaris Magnum 500 when cold. It's fires right up. Can drive around ok. But when I turn off the engine, it won't start again for a number of hours.

I'm trying to do what I can before hauling it to a garage. So I can't set the RPMs to a fixed number, and don't know the compression. I set the idle by ear, which does not mean much. It sounds much better after the valve clearance adjustment.

This is a brand new spark plug after 10 mins of running. It looks way better than when I started fixing this machine, but still not good enough.

This is my carb float overflow. It doesn't drop, but I see a drop hanging.

When I rev the engine, I see a bit of black smoke, like it's blowing out carbon. I have to wait a few seconds for the RPMs to go back to idle, so I can change gears.

I cleaned and rebuilt the carb. I replaced the fuel lines. And I set the valve clearances. Need to figure out what to do next.

I ordered a new fuel pump. The one I have now was full of dirt, so I carefully cleaned it. It's sort of working, but it doesn't keep the line from the pump to the carb full. There are air bubbles.

When I try to start when warm, there is gas at the carb. The engine turns over but won't fire. I have a good spark. I cleaned and dried the plugs, but no luck. I just have to wait for it to cool off.

What can I check with my limited tools and experience, before raising a white flag for a mechanic?

I have the service manual checklist, will go through that too. Hoping to narrow this down better.

 

BTW - not a fuel vent issue, vent line is clear.

 

Compression should be between 55-90 psi on average because of the compression release device. Even if you show between this amount still could be leakage from valves or rings causing plugs to oil up This is where a leak down test can tell.Plus if the carb is dripping,sounds like the float level is off.

 

I can adjust the float. But I'm guessing I'll have to go to a garage to get a leak down test and a compression test?

 

 

Looks simple enough, thank you!

 

I took my ATV to the shop, rather than buying a leak down tool. They told me the motor had jumped the timing chain. They found 100% leakage, which led to this finding. So I have to fix this.

Question: they weren't sure if this is an interference or a non interference motor. How can I find out? The valves may be bent, but won't know till I reset the timing chain.

 

Jumping timing is usually either from a worn out cam chain or a lower crank sprocket woodruff key may have broken throwing timing off. I believe the Sportsman is a non interference engine as the only time I've had bent valves is when a piston grenaded. The Predator 500 on the other hand is an interference engine for sure as I've had to replace valves on these several times when timing was off. Fix the timing problem first. If the head has to come off later not that big of a deal as you can do it with the engine in the frame.

 

I was going to reset the timing to see if it happens again. How can I check the woodruff key without pulling the flywheel! There is damage to the flywheel fins was from a former owner, could this have messed up the timing? The fins are intact, I think they had the recoil starter installed the wrong way.

 

Attaching photo of flywheel damage.