Wouldn't worry about how long it'll last.. Just ride and enjoy..

 

It lasted until this week. The longest stretch I have had. Now it will not start. I have good voltage and spark. There is now gas in the airbox. Any suggestions?

 

Check compression,should be between 55-90 psi on average. May help to to pull the valve cover and check the valve clearance.Tight valves can cause fuel to spray back into the air box as well as needing a good carb kits also.Polaris Sportsman 500 Carburetor Repair Kit Fits 2001-2002 Carb: Shindy 03-408 One other thing to check is if the flywheel key may have sheared.Just remove the recoil cover and flywheel nut and you can see if it has or not.

 

Also just found my mysterious gas leak. It is leaking where the exhaust pipe meets the fitting coming off the engine. Does that correlate to anything you mentioned?

 

Yes sounds like combustion chamber may be flooded and fuel leaking out the exhaust. Again this can be carb related,valve related or possibly a sheared key. If you take a carb off rebuild it,don't just clean one.Plus a sheared key can cause problems like this by not being able to burn fuel correctly or at all if the key has sheared to where timing is way off.Just a process of elimination. Check the valves and compression then check the flywheel key. If these check out,you still have good spark,then head towards the carb.Hard carb to set float level right,but this may help on this BST40 carb.The BST-40 Bible | Adventure Rider
Polaris Sportsman 500 Carburetor Repair Kit Fits 2001-2002 Carb: Shindy 03-408 | eBay

 

The key is not sheared. Can the carb be rebuilt without taking off the throttle and choke cables?

 

Yes you can leave the cables attached.A little harder this way rather than on the work bench though.See if the carb section from the manual helps. https://www.google.com/url?sa=t&rct=...U2gGlaHJWSIlbA

 

Got the carb rebuilt. It started up and ran fine--maybe a bit rich--for about 10 minutes and then died. Looked in the air filter box and it was half full with oil and gas. Now I guess I take the whole thing apart and look at the valves?

 

Hopefully you did replace the air filter. Still sounds like carb related especially if you don't have the float adjusted properly.Hard carb to get right.Here's how to adjuts one,plus you can use a clear tube on the carb drain bow nipple to see if fuel rises above the bowl.Also check the oil tank ad see if it's overfull or smells like gas. Change the oil and filter if needed.

 

Thanks. New air filter. I hope it is the carb. As a side note, the carb mounts to the frame with a rubber bushing through the frame with a bolt and nut. The passenger side has the bushing but no bolt. I assume this is wrong and should be mounted like the left side?