I have a 1996 Polaris sportsman 400 that just got a new top end put in. On the first time getting her out on the trails overheated and died on me. Now it just won't fire back up at all. Gas is good, oil is good, carb is cleaned,air filter good, new spark plugs also. The only thing is the electric start doesn't work and the headlights don't either, but they weren't working when I was riding it I the first place anyways. Any suggestions on what could possibly be wrong?

 

First off did you bleed the 10mm screw on the head to purge trapped air from the engine cooling system? A lot of people forget this and can seize up a brand new top end,blow head gaskets,etc when they overheat. Do you have spark when you ground the plug at the cylinder? Have you checked compression?,should be at least around 135 psi or more with a new top end.
If compression is still ok and you've bled the head,but don't have spark,pull the black wire from the cdi and see if you have spark,if still no spark pull the black wire from the reverse limiter module and see if you have spark. Also make sure the tank vent is clear and you have fuel to the carb. IF none of this helps,could be stator,cdi related and resistance checks may be needed. LOT of things to check,but check each thing one at a time to eliminate it as a problem. OPT

 

Compression is good, spark plug has spark and carb is clean and is getting fuel as well, but I don't remember if I bled the head or not. I guess that'll be the next thing I try. Spent all day messing with the bike yesterday, so I made sure everything was clean. The electric start wasn't working already and that was the first thing I was going to tackle but it overheating comes first.

*****update***** found the reason for overheating, the muffler wasn't attached to the engine all the way and was causing it to overheat. Still no pull start though, any help is greatly appreciated.

 

Bleed the 10 mm screw at the back of the head even if you don't remember doing it just to make sure!!(don't take it all the way out) near the temp sensor,let the coolant flow out until no air bubbles are seen. If the pull start doesn't work then pull the recoil cover and see if you can turn the flywheel by hand with the plug out. Hopefully you don't have a piston seizure. Loose muffler shouldn't have caused it to run that hot. Good luck OPT