Hi, I have a '96 polaris magnum 425 that misfires badly from around half throttle and up. It maxes out at 20 mph like it is hitting a rev limiter. I have adjusted the valves to spec (.006), cleaned carb thoroughly (with carb cleaner and compressed air), changed fuel filter and air filter, new fuel lines, new fuel pump, new fuel shut off valve. The Etc was cut/disconnected when I bought it. There is a higher octane gas in it right now (90 octane). The bike ran great then 2 days later it just starting doing it. nothing changed between when it was working good and then bad and misfiring. Im at a loss as what it might be, I have read about the cam lobes wearing down but would like to start with the simple less expensive ideas first before trying that.

Any ideas are welcome and appreciated,

Thanks.

 

If you haven't done so already pull the black wire from the reverse limiter(#33) at the terminal board and see if that solves the missing.

 

Thanks for the reply, that black wire was disconnected when I bought it so I think that might be ruled out.

 

There's two listed. Pull the other one also if it's still plugged up.Been too long but you may have to pull the tank plastic side cover to get to it.

 

oh ok I see the other one, I'll give it a try tomorrow and get back to ya.

 

I tried pulling the second wire (#33) and got nothing. I also tried following others and trying them and making sure everything is plugged in and haven't gotten anything. I also tried putting a bit of sea-foam in the gas tank but also got no results.

 

If you just cleaned the carb and didn't rebuild it that could be part of the problem.https://www.ebay.com/itm/Polaris-Mag...lnJj-g&vxp=mtr If that doesn't solve it then I'd measure the cam lobes. Cam may look good to the naked eye but exhaust lobe could be worn down enough to cause this limiting problem.

Plus you might want to check the decompression spring and lever that it's working right. If the spring slips or breaks it can cause limiting also.

 

Thanks for the ideas, The carb was bought new by the previous owner (doesn't mean that's true though) and it looks to be in good condition. The part about the decompression is interesting because ever since we adjusted the valves it has been hard to turn over with the recoil and certain strokes need to have one foot on the bike to pull it.