TOPIC:

George,

Thanks again for the great advice.

Happy holidays,

Dave

Isn't WG great? Love having him around!

SIKZ250 wrote:

Thanks George!

I decided on a Uni pod filter and tried a few
different jets. The bike now runs pretty well with the #130 secondary main.<br><br>Post edited by: SIKZ250, at: 2007/08/20 21:38

Isn't a 130 main jet a little too much? The 250 have got a 98 as stock, and going up to 130 seems a little over the edge.(The largest main jet listed for the KZ250 is a 102 jet for racing.)
Also the 250 carb doesn't share it's jet needle or needle jet with any other Kawasaki carbs. Assuming you can use the KZ750 carb configuration probably won't work either.
Anyways, you need to read the spark plug to get the mixture correct. It could be that the popping is caused by after burning unburnt fuel in the exhaust caused by a too rich mixture.

With the Uni pod filter, there is very little air restriction, so 125 to 130 jets work pretty well. I moved up to a 130 for the winter as the bike runs better. My understanding is that backfiring during deceleration usually indicates a lean mixture, which may result from an air leak in the pilot circuit which gets fuel through the main jet. I haven't had any luck finding a #70 main jet, so I'm still fighting that battle. Hopefully changing the pilot screw gasket and cleaning the passages around the screw will help.

Pilot screw gasket? There is a rubber oring under the pilot mix screw and there may be a plug in the pilot well but I can recall no gasket. I doubt the backfiring is due to a leak... most likely a larger pilot jet or even the larger main jet I already suggested would help. You may be able to tune some of the backfiring out by adjusting the pilot mixture screw.

Oops... o-ring

wiredgeorge wrote:

Pilot screw gasket? There is a rubber oring under the pilot mix screw and there may be a plug in the pilot well but I can recall no gasket. I doubt the backfiring is due to a leak... most likely a larger pilot jet or even the larger main jet I already suggested would help. You may be able to tune some of the backfiring out by adjusting the pilot mixture screw.

That was a great tip, George. The pilot screw head is very close to the plug, but I drilled through the plug very slowly and didn't cause any damage. The plug was held in place tightly, so I used a soldering iron to melt the glue and it came right out.

I rode around the neighborhood, stopping every so often to fiddle with the pilot screw. Backing it out a few turns really smoothed out the idle. The backfiring may be reduced a bit, but I also plugged a small hole in the exhaust which may have helped. There is still some popping on deceleration, so I guess I have to try to find a #70 main jet (easier said than done).

Thanks.

wiredgeorge wrote:

I recommend you buy a small EZ out... probably a #2 and buy the associated correct drill bit. Use a punch to mark the center of the plug. Use the drill bit recommended for the EZ out and slowly drill the plug. It is easy to get through the plug and nick the mixture screw below so go slow and be careful. After you drill through the mixture screw, insert the EZ out and see if the plug will move easily. If it doesn't you might want to use a torch and warm the glue...