I have a 500 screambler was riding it about 10mins yesyerday and it started to backfire and bog really bogged off idol carb is cleaned and everything the plug looks good tannish brown color. replaced fuel pump diaphrams cause the fuel pump would not hold pressure. iam stumped any help would be great.

thanks

 

I had the same problem on a brand new sportsman 500 and it turned out to be the fly wheel was miss alined and the sheer pin was gone, not sure if this is your problem but might be worth looking at.

 

how would you tell if it is misaligned?

 

The sheer pin is cut through a little or all the way, in my case the sheer pin was cut in two and my machine would back fire like a shot gun when started and if it kept running it was gutless.

 

Check the secondary clutch buttons

 

Here is my standard answer, check your valve lash and cam.

 

valve lash is good cam does not look bad

 

Had same issue on my 1998 scramerler

 

hey be sure to check the exhaust lobe on the (middle lobe) i have an 01 sportsman 500 that i was having the exact same problem with and it turned out lack of adjustment caused it to wear the lobe down to nothing and ended up replacing cam.if thats the case babbitsonline.com is cheapist i could find my also want to consider changing rocker arm as well let me know if this helps at all

 

cdi checked good 138dcv center cam lobe looks good im stumped any other suggestions could it be something electrical that is heating up after riding it for so long? looking at the cdi closer it was broken in a rollover could this cause problems while it running the case is broken at the top.