Hello,
working on a friend's kawasaki bayou 220. It wants to surge when going at very low speeds (above idle to about 1/8 throttle). Friend said he thought head gasket was issue but I took carb cleaner and sprayed all around the head with no change in engine rpms that I could notice. If I can find my starting fluid I can try this method again with a slightly more volatile fluid. To me this says the head gasket is fine. If the rpms changed, then i would agree on head gasket. Atv seems to run just fine above 1/8 throttle all the way to full.

Any ideas on what could be the issue? I will be taking spark plug out once the engine cools off. I have not had a look at that yet. Otherwise it seems to idle just fine for an atv, doesn't sound too low or too high.

a weird thing was the issue seemed to go away in 2nd gear and up, with occasional miss. The miss is telling me to look at spark plug. But wouldn't this issue persist at all rpms if the spark plug was the cause?

 

Change the plug anyway, it is a service item. Most likely cause of the problem is a partly blocked jet, so it has trouble going from the idle jet to the main jet. If a new plug doesn't fix it, clean the jets and the holes they came from out with compressed air and see if that helps. Make sure the choke is working properly, and that there isn't an air leak in inlet manifold.

 

Choke works. I can move the indicator back and forth and engine rpms change as choke is applied/removed. When I sprayed the head with carb cleaner, I also sprayed from the head to the airbox. I was thinking if there was a air leak, it could be from the boot between air box and carb. I also sprayed the mating surface where carb meets head (or I think I did). That did not make a difference. Spark plug looked great last night when I looked at it, slight grey appearance. Not wet. Will pick up replacement plug tonight as well as a new bottle of starting fluid (old bottle up and walked away).

My dad and I were reviewing other forums and think the issue may be ignition related. The battery in this ATV is dead dead. I attempted to see if it would take a charge by trickle charging it for 2 days at 2A. Battery shows some sign of life (lights up neutral indicator) but won't turn on headlights or even make a clicking noise when starting. I am wondering if the battery is robbing power from the stator/generator (basically being a massive drain) and the engine does not turn fast enough at low RPMs to overcome this drain occasionally. Could this be a possibility? We were also thinking since the ATV is 20+ years old now, the stator and/or generator could be going bad now. My plan to test this is
1) remove old battery, pull or jump start ATV, see if problem disappears or persists with no battery in ATV (battery leads taped to prevent short).
2) install good battery, start ATV, see if problem disappears or persists.

If either of those 2 tests do not work, then it will be down to carb issue. My friend said the carb was rebuilt recently. The person who rebuilt carb was also blaming the issue on head gasket.

 

Kawasaki were a bit "different" with regards to ignition systems. The 300 had 1980s car type ignition with 12v coil. However I'm fairly sure the 220 was AC CDI, this means the ignition system is totally separate from the battery system, so a flat battery, or non charging alternator, won't make a blind bit of difference. As I wrote earlier, the problem is probably a partly blocked jet. If a plug doesn't fix it, check that before going into the ignition system, which can end up expensive.