TOPIC:

I received the new 17.5 pilots and 110 main jets today and stuck them in the carbs, along with new needles and now the pig is popping and snapping at an idle and when I accelerate, it snaps and pops out the carbs!! Am I doing something wrong?! When I accelerate smoothly, it picks up ok, but it "pops" through the carbs...I adjusted the air screws to 1 1/2 turns from snug...is the mixture maybe too rich? HELP!!!

Check your carb manifolds-boots. They get old, dry out and crack. This is probably your easiest troubleshooting step.

Get the motor running and spray some carb cleaner around the rubber boots. If the motor picks up the revs you probably have a cracked or leaking boot. Just to be sure remove the boots and put on a thin bead of 3 Bond gasket material on the surface where the boot mates with the intake ports to give a good seal.

If this doesn't solve your problem it might be ignition/coils. There is a lot of threads in the archive about popping carbs.

Cheers-Colin Firth-Ontario Canada
1977 Kz 650 being rebuilt (again) with 810 kit, WG Mikuni 28 carbs, Dyna Coils and Ignition. Mac pipe, Ported 650 head, 750 cams, 750 Intake valves and springs.

Okey Dokey...Will give it a go...thanks

I put the Stock main jet back in and left the 17.5 pilot in and the popping and spitting stoppped, but it is still running lean, (white plugs)...should I maybe mess with adjusting the air screws? I checked the rubber boots that connect the carbs to the head and there are no visible cracks...What should I do next to try and adjust the carbs so they run a little more rich, but not too rich so that it loads the motor up?

You could try raising the jet needles one notch, keeping in mind the jet needles control the 1/4 throttle to 3/4 throttle fuel mixture.

I would quit messing around with jetting till I found the air leak (symptoms popping and lean burn on plugs). REPLACE your intake manifolds/use stock type (thin) clamps, REPLACE the vacuum caps on your intake manifolds and replace the orings on your mixture screws. THEN see if the popping goes away... if still popping, it is likely the idle mixture is misadjusted. This is all assuming that your bike is otherwise correctly tuned... Oh yeah... I would also pull the head pipes off your exhaust and replace the crush gaskets.

Post edited by: wiredgeorge, at: 2006/04/06 12:01