Cyl #2 & #3 sooty or rich

Hi,

Plug #2 and #3 are consistently sooty when I pull them out in the garage and I can't figure out why. Bike starts and runs fine, but I think it could run better.

Poor Spark?
- Voltage to coils is strong (coil mod done).
- Swapped igniter circuits with no effect.
- Swapped pickup circuits with no effect
- New plug caps, new plugs.
- coil resistances check out fine as per manual.

Too Much Gas?
- starter plungers on 2 and 3 look fine.
- float levels within spec
- stock pilot jet installed (15)

Not Enough Air?
- Air filter is clean
- new airbox boots
- Carbs synched


What do you think of these other possibilities?
- blockage in 2 & 3 exhaust?
- carb holders leaking? (wouldn't this cause leanness?)


What else could it be??? This is annoying me, and seemed to begin after I rebuilt the carbs and added electronic ignition (don't know which one did it).

Have you checked the valve clearance? You could try a leak down or compression test.

Concur with suggestion to check compression and valve clearances.

New plug wires also?

Fat blue spark?

Sounds like a classic case of 1 & 4 not firing.:woohoo:

You didn't mention how many miles are on the motor, but here's what happens often with well-ridden Kaw 4 cyls. Because there's so much interfering with front-to-back air flow through the passages between cyls 1 & 2 and 3 & 4, the 2 middle cylinders run hotter than the outer ones that get all that good exterior wind. This causes their rings to wear faster, and a gradual drop in compression over time. As compression starts flagging things like you've described start happening. Check the cranking compression on all 4 cyls -- if the bike's been well used I expect you'll see significantly lower readings on 2&3. My 1st Z1 started acting sluggish and sooting up plugs, etc. after about 85,000 touring miles -- a compression check showed it was running on 110 lbs. on 1 & 4 and about 25 lbs. on 2 & 3, just enough compression to make it seem like something else was wrong <lol>. New rings and a litle valve cleanup was all it took to get that nice punch back.

Good Luck!
OldRobP

You didn't mention how many miles are on the motor, but here's what happens often with well-ridden Kaw 4 cyls. Because there's so much interfering with front-to-back air flow through the passages between cyls 1 & 2 and 3 & 4, the 2 middle cylinders run hotter than the outer ones that get all that good exterior wind. This causes their rings to wear faster, and a gradual drop in compression over time. As compression starts flagging things like you've described start happening. Check the cranking compression on all 4 cyls -- if the bike's been well used I expect you'll see significantly lower readings on 2&3. My 1st Z1 started acting sluggish and sooting up plugs, etc. after about 85,000 touring miles -- a compression check showed it was running on 110 lbs. on 1 & 4 and about 25 lbs. on 2 & 3, just enough compression to make it seem like something else was wrong <lol>. New rings and a litle valve cleanup was all it took to get that nice punch back.

Good Luck!
OldRobP

You didn't mention how many miles are on the motor, but here's what happens often with well-ridden Kaw 4 cyls. Because there's so much interfering with front-to-back air flow through the passages between cyls 1 & 2 and 3 & 4, the 2 middle cylinders run hotter than the outer ones that get all that good exterior wind. This causes their rings to wear faster, and a gradual drop in compression over time. As compression starts flagging things like you've described start happening. Check the cranking compression on all 4 cyls -- if the bike's been well used I expect you'll see significantly lower readings on 2&3. My 1st Z1 started acting sluggish and sooting up plugs, etc. after about 85,000 touring miles -- a compression check showed it was running on 110 lbs. on 1 & 4 and about 25 lbs. on 2 & 3, just enough compression to make it seem like something else was wrong <lol>. New rings and a litle valve cleanup was all it took to get that nice punch back.

Good Luck!
OldRobP