low rpm surging?

Hi. KZ900 header and pods. 120 mains. 20 pilot.moved the needle up one notch, so it is the fourth notch up. factory is in the middle i believe. brand new inline fuel filter. ok question. i'v got low range surging. just when im starting from a stop. it hesitates a little.when i cruise low rpms slow it surges. half throttle and wot are great. also when is start it up it doesnt start like it did before i switched my jets. i cant tell if im getting to much gas or not enough. ive been messing with my throttle when i start it. is this pilot or fuel levels maybe? im thinking its got to be carbs.

Too rich. Bogging is lean condition Surging is rich condition. Go back to stock pilots and only raise the needle one notch from stock. Lean out pilot screws to max Hi idle, not to book settings.

Surging is usually caused by rich, but I do remember when mine was new they had super lean pilots (california) and it would stutter in the 2200 - 2600 range which was sort of like surging.

asevans wrote:

Hi. KZ900 header and pods. 120 mains. 20 pilot.moved the needle up one notch, so it is the fourth notch up. factory is in the middle i believe. brand new inline fuel filter. ok question. i'v got low range surging. just when im starting from a stop. it hesitates a little.when i cruise low rpms slow it surges. half throttle and wot are great. also when is start it up it doesnt start like it did before i switched my jets. i cant tell if im getting to much gas or not enough. ive been messing with my throttle when i start it. is this pilot or fuel levels maybe? im thinking its got to be carbs.

Oem KZ900 carb is 26mm Mikuni manual slide with side located pilot air adjustment screw.

Jet needle has five clip positions. Oem clip position is middle.

Moving the needle "up one notch" is usually interpreted as raising the needle so as to enrichen the mid-range. This would mean moving the clip one position down closer to the tapered (pointed) end of the needle.

Could experiment by adding a little choke during the surging.

If performance improves with choke added, something is causing a too lean condition.

If surging worsens with choke added, something is causing a too rich condition.

The oem KZ900 26mm carbs are very user-friendly, and may do just fine with jet needle clip in the oem middle position.

Good Fortune!

What Patton said about the choke is very true and makes a simple and reliable test.

when i mess with my air screws its hard to notice any change. they do cause a reaction when i turn them in. like the manual says. but as far as finding the right setting, it is hard. right now they are 1 1/2 turns out.

asevans wrote:

when i mess with my air screws its hard to notice any change. they do cause a reaction when i turn them in. like the manual says. but as far as finding the right setting, it is hard. right now they are 1 1/2 turns out.

when i mess with my air screws its hard to notice any change. - - - This may result from imperfectly cleaned passages in the carb pilot circuit.

Good Fortune!

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Wear protective goggles while using carb cleaner spray.