I was driving my 500 cat and when i would left off the throttle the muffler would backfire just a little bit, my son's atv was doing the same but when i cleaned the gelled gas out of it, it works great. I tried doing the same to mine and now it will not idle right, high speed OK but not idling, i have replaced all the jets and polished the inside like a mirror but no change, I sent it to a atv mech and was told the carb was bad and needed replaced but how can this be? I have never had a single problem with this bike and I am thinking maybe a voltage problem causing a low spark? and yes I have changed the spark plug serveral times. the bike will load up at a idle but will run fine at mid to upper throttle, anyone else run into this? I would really not like to spent $400.oo for a new carb and stilll have this problem. Thanks for your help..

 

New carb? carbs don t wear out you clean them at the least and intall a carb kit at the most.

 

Sometimes idle/ hard starting issues can be casued by the valves being out of adjustment or a choke problem.

 

Well I have installed a carb kit and polished the complete inside like mirror and nothing has changed, I must of torn that carb apart over 25 times to make sure I wasn't missing anything. I don't think that it is a choke issue cause I can tell when the choke is applied. and as far as the valves go, would the bike run fine at a higher idle? the bike isn't backfireing after I cleaned the carb just won't run right. does anyone supect a voltage problem? like the spark plug isn't getting a hot enough spark at a lower idle?

 

the bike will load up at an idle and when i gun the throttle is blows black smoke out. and the plugs are heavily sooted.

 

Black plug means its running rich so it is getting too much fuel and not enough air somehow. If this is an older machine the choke is a fuel enrichment system and lets more fuel in at start up. There is a little plunger that is part of the choke that sticks and even though the cable moves the plunger does not.

If this is a newer machine with the electric fuel pump I might check to make sure it is operating correctly.

You could check the peak output voltage of the magneto. I should be 220W at 5000rpm. Most of the time you can just check your charging systems output voltage across the battery terminals at an idle. I think it should be between 12-13 volts. Then if you punch the throttle the voltage should spike some.

Best way to check spark to the plug is with an inline tester. plugs in between the plug and the wire and it is a little light that flashes when voltage passes through. Sometimes you can notice how bright it is.

SJ

 

Thanks I will look into the plunger on the choke cable, I did not think of that, I was looking into the carb only and did not think about the plunger getting stuck. that makes sense. Thanks

 

I dont know if this will help much but it worked on my 03 400. on the side of the carb where the throttle cable attatches, there is a cable about 4 inches long and it has a black gear looking deal on the end of it. turn it clockwise to increase idle. i found it by accident.