26mm mikuni carb adjusting??

I have a 1977 KZ1000 LTD. It has the 1100 kit and heavy duty valve springs. Everything else is stock as far as air box, original 26mm mikuni carbs, exhaust. It pops on decelleration, but still runs good. My question, is there a need to rejet the carbs? Do you think it needs more gas? Would adjusting the jet needle be ok? Maybe try the #4 position on the jet needle? Or just rejet altogether? Any info will greatly be appreciated. Thanks

If the only change to the engine was making it bigger and the bike runs good then I would leave the carbs alone. If you are getting popping on Decel. that indicates a lean idle circuit. Did it do this prior to the larger bore, if not then go to the 17.5 pilot jets.

try to find some 28's 20/120. unless you can afford smoothbores, flatslides .

cam9281 wrote: I have a 1977 KZ1000 LTD. It has the 1100 kit and heavy duty valve springs. Everything else is stock as far as air box, original 26mm mikuni carbs, exhaust. It pops on decelleration, but still runs good. My question, is there a need to rejet the carbs? Do you think it needs more gas? Would adjusting the jet needle be ok? Maybe try the #4 position on the jet needle? Or just rejet altogether? Any info will greatly be appreciated. Thanks

If carbs have side-located pilot air screws, could adjust each screw by turning 1/2 turn clockwise (which enrichens the pilot circuits), and test run.

If carbs have bottom-located pilot mixture screws, could adjust each screw by turning 1/2 turn counter-clockwise (which enrichens the pilot circuits), and test run.

Am presupposing that there's not an issue with "racing idle" which might indicate one or more carb-holder air leaks, which could also cause or contribute to popping from exhausts on deceleration, due to leaning the mixture.

Good Fortune!

Thanks everyone! The pilot mixture screws are located on the bottom of the carbs. I had them 1.5 turns out and it stopped the popping, but on cold start up the choke doesn't like to stay on very long so I have to shut it off and then I have a hesitation off idle for a few minutes until the bike warms up. Not sure what that means

Assuring valve clearances within specs, plus brand new NGKB8ES spark plugs, accompanied by spot-on ignition timing, and no carb holder air leaks, followed by a good carb sync, should help produce a steady idle with strong pull-away.

It's not unusual for the choke lever to require constant attention and gradual reduction while the engine warms to normal operating temperature.

After starting a cold engine, I prefer reducing and disabling the choke asap, and riding moderately while the engine warms to normal operating temperature.

Especially if the battery happens to be a little low, getting off choke asap will help prevent possible flooding and non-combustion in one or more cylinders due to weaker spark until the battery recovers.

Another helpful technique is to ride the first few miles with the headlight turned off, which affords a stronger spark while the battery recharges.

Good Fortune!

Thanks Patton! I will double check the above mentioned. Would it be ok to adjust the jet needle position for a little more gas? Or just leave it at the stock setting?

cam9281 wrote: Thanks Patton! I will double check the above mentioned. Would it be ok to adjust the jet needle position for a little more gas? Or just leave it at the stock setting?

Would suggest leaving the jet needle in stock position (thinking middle clip), as the jet needle doesn't influence choke function, or idle (pilot circuit mixture), or popping on deceleration.

The jet needle position primarily influences fuel mixture in mid-throttle range.

Good Fortune!

Thank you. Not to keep harping on the jet needle setting, but in your opinion do you think I would see any improvement in the mid-throttle range if I adjust the jet needle maybe to the fourth position? Since it does have the 1100 kit? Just curious.

cam9281 wrote: Thank you. Not to keep harping on the jet needle setting, but in your opinion do you think I would see any improvement in the mid-throttle range if I adjust the jet needle maybe to the fourth position? Since it does have the 1100 kit? Just curious.

While a larger displacement may combust more fuel mixture in the mid-throttle range, it doesn't necessarily require a richer fuel mixture.

Absent a noticeable deficiency in mid-range performance with the stock jet needle clip position, that's reasonably attributable to an excessively lean air-fuel ratio, would suggest leaving the clip in it's stock position.

Operation in seriously cold weather at sea-level (dense air) might require raising the jet needle (lowering clip position) to maintain the same air-fuel ratio supplied in moderate weather riding at more normal elevations.

Riding at very high elevation (thin air) may require lowering the jet needle (raising clip position) to maintain the same air-fuel ratio supplied in moderate weather riding at more normal elevations.

Spark plug readings are another means for determining appropriateness of air-fuel ratios at various throttle positions.

And there are several threads with information about ideal air-fuel ratios, and how to measure them at various throttle positions.

Good Fortune!

cam9281 wrote: Thanks everyone! The pilot mixture screws are located on the bottom of the carbs. I had them 1.5 turns out and it stopped the popping, but on cold start up the choke doesn't like to stay on very long so I have to shut it off and then I have a hesitation off idle for a few minutes until the bike warms up. Not sure what that means

It means nothing. It's normal. Ride it.