I have a 2008 smortsman 500 H.O. Machine starts Idles and runs perfect for about the first mile and a half. It seems once it gets up to temp. it starts to spit n sputter, backfires, and loses power, if I don't keep jabbing the throttle it will stall. If it does stall, I have to choke it to get it to start. it continues to run like crap. If I let it cool down for just a short period of time, it will run perfect again. Wondering if I might have a coolant sensor issue... If so where is it and how do I test to see if it is failing? Or does anyone have any other Avenue for me to pursue? Weathers getting nice, would rather be riding the machine that working on it. been chasing this down for some time now...

 

Welcome to the forums.

Have you pulled the plug when it starts acting up to see if it's wet?

Some of the other guys that are a little more familiar with this should chime in soon and hopefully they'll get you the quick and easy fix.

 

I haven' pulled it after it presents the symptoms, but i did change the plug, the old plug was in pristine condition. however, noe that you mention it, the spark did seem a bit weak... In my opinion.. i kind of dismissed it given that the issue only presents itself at certain derees of temps... Or so it seems...

 

You might want to run a quick compression check also.

 

Do you think compression would cause an intermittent issue, I was thinking it would be more constant.. Although I’m not overly qualified in troubleshooting these machines

 

If it were a two stroke, what you described is how it would act. Starts fine when cold, gets hot and loses it's compression and runs like crap or won't restart till it's cold. Mine were all simple running machines, the new ones today have a whole lot more to go wrong with them.

Just kinda giving you ideas to look at for now. Someone on here has probably had this problem and will come along and show you my idea were probably way off the mark.

 

You haven't seen way off the mark till you see some of the things I've been chasing with this problem, any suggestions are welcome. It’s funny how we let this sort of thing consume us… Seems to be all I can think about right now… Glad I have a cool boss….

 

Hiya "Can't" ... I know that with the Polaris' the valves have to be adjusted every 100 hours. The intake valves get real tight and won't allow proper 'seating' and the exhaust valve gets loose. Just adjusted one that was 130 hours over-due.... Intake was every bit of 3,000th's out of adjustment and exhaust was 1,000th's the opposite.

Also the coolant sensor is on the belt side of the engine. Just below the jug. You'll see it; it has a wire coming out of it. I don't think tho, unless your temp gauge isn't working, that this is your problem. Sounds to me like you need to clean your air cleaner and possibly clean your carb. (Just a suggestion)

 

I took apart and cleaned the carb, I think it was somewhat of an improvement, or I just wanted it to be… I did clean the air cleaner, as about the time this happened, the machine was on its top, (upside down) I did notice however, that the boot from the air cleaner box to the Carb is dry rotted, do you think this could cause my problem? I don’t really want to start throwing parts at it, needlessly… could get expensive.

 

Silly question: Why was your bike upside down??? Did it JUST start doing this after being upside down?