KZ750 4 - 1/8 Throttle Stumble

Will pull the carbs back off this weekend and go at the pilot circuit again and record the jet size. Hoping to get his all done before riding season really sets in.

Pulled them off today and re-cleaned the passages. Blew compressed air through, still no changes. The plot jets are size 35. Plugs are white or very light tan after a 50 mile ride today, looks like an overall lean condition then. I did notice with the colortune in that the "stumbling" RPM range (~2500) it is not consistent and there are frequent bright flashes in the cylinder.

I have checked ignition advance and timing.

Not sure what next steps would be?

Finally got this corrected! Jets appeared to be the right size for the stock setup and I remember riding this same bike 10 years ago and it was fine (used to belong to a good friend). It had symptoms of being lean throughout the throttle range so I was thinking back through everything that I had replaced. I replaced the float needles last fall AFTER I had set the float heights earlier in the season. I checked the levels last night and they were all over the place. Pulled the carbs and wet set them on the high end of the range, could tell the difference the minute I started it back up. Had a beautiful ride into work today.

Thanks for the pointers, hopefully this helps someone else. Those float heights are extremely important. It never ceases to amaze me the life that you can breathe back into these bikes with simple maintenance. This bike was near death, did shims, rebuilt carbs, new intake boots, plugs, vac sync and carbtune. :woohoo:

I know this is old but I wanted to update it in case anyone else read it. While the fuel levels were incorrect and adjusting those helped considerably, the final fix was replacement of the carb holders. The propane test did not reveal the issue but when I retested by spraying carb cleaner around the intakes it increased the RPMs. Now that those are tight again the bike runs fantastic.