hi
my zark backfires sometimes like 3 or 4 times in a 5 hour ride what coul it be?

 

My friend has an ozark and when he holds it wide open for a while like running on the road and when he lets off the gas is when it starts to back fire, he did not break his in properly he beat on it pretty good so i dont no if that is why his backfires

 

my vinson did it when it was new. i think after the valves seat it goes away

 

Usually a backfire indicates the bike is running too lean or an exhaust leak exists somewhere.

If it happens when your're slowing down, it could be the idle mixture is set too lean. As the bike transitions from the needle circuit (1/3-2/3 throttle) to the idle circuit (0-1/3 throttle), the backfire would occur.

You can easily fix this by turning the idle mixture screw 1/4 - 1/2 turn out (counter-clockwise) and try it. This allows the bike to idle a little richer. If this works, you may need to set the idle speed to spec.

Hope this helps.
Mark

 

Backfireing is usually caused by a lean condition, especially on de-celleration. Given the fact that most bikes that are sold in the U S are very lean to meet E P A specs. Larger mains or idle jets will help, or raise the needle a notch and turn the idle mix screw out about 1/2 turn at a time.

KFXBob

 

thank u all

the local dealer sent my zark to a central distributor it seams there is something wrong with the valves and the overall tinnung of the motor i ride my zark preaty hard, it as never let me down, wonderfull litle bike, hope i can give her a bit more power , thinking about the T4 procircuit and the KN filter what do u think?