Nibbi PEZ28 on 2024 CSC TT250

[Sdmfjon]

Hello

I can now confirm the Nibbi PEZ28 is a direct fit for the 2024 TT250. I did not have any issues with fitment. This carburetor sits almost exactly where the stock Keima sits. The throttle cable is just long enough to work. I did not have to modify anything to make it fit.

Tuning on the other hand, this is where I'm at.

Fully stock bike with emissions removed and a Nibbi PEZ28 carburetor fitted. I am in Maine and live at the beach. My elevation is less than 50' and it is summertime. Sunny day and about 85 degrees air temp.

Idle jet - 38 (factory was a 40 and too much for my stock setup)
Air screw 1 and 1/4 turn out ( factory is 1 and 1/2 )
Needle - position 3
Maine jet - 110

Idle is beautiful and strong. WOT is ok. Midrange needs adjustment.

I still can't quick throttle without it dying. I can roll on and it is fine. Only had like 45 mins to tune before having to go to work.

The max jet the carb came with is a 110. I think I either need to mess with the needle or change to a 112.

The air screw on the side is awesome.

[ProDigit]

First try to lean out the mixture with the AF screw. 1/2 to 1.5 turns.
If that works, and you're happy with wot performance, then lean out the mixture by lowering the jet needle (raising the clip), and resetting the AF screw back to before.
It'll reduce low rpm torque, but if it gets rid of the stalling, you'll have to find that perfect acceleration setting.

If it got worse by leaning out the mixture with the idle screw, try richen the mixture by 1/2-1.5 turns, and see if that improves throttle response.
If it does, raise the needle instead.

[red2003]

If the carb is starting well with the choke, and has a good clean idle, leave the pilot jet and air screw alone. If briskly opening the throttle causes the bike to cut out, the needle needs to be raised. One notch can change a lot. Try position 4 and test. You should notice a difference. If it still cuts out even after it's warmed up and under load, you could try position 5, but I doubt it will need that much more fuel.

[bigdano711]

Take picture of needle. I will do the same since I yanked it out of my Nibbi PE28FL. I will lay it next to a Keihin needle and you will see obvious differences. The best solution for me in the mid was a Keihin JJH. Didn't I JUST type this recently......?


I got this needle/jet kit off Amazon. I can find the link if anyone is interested. I had no idea they were Keihin clones. You can see in the macro pic that the entire adjustment range is lowered, yet there is significant overlap. I tried every position on the Nibbi needle, with no jet changes, and could not discern any kind of appreciable difference from one setting to the other. Maybe yours will be different as there is a significant altitude drop from me to you. I read on some other forums about guys having really good luck with the JJH and, since I had one to try, I figured what the heck. I got immediate feedback, letting me know my pilot jet was too large. Adjusted that back down to 38 and slowly worked my main jet down as it was too large. I am now at 38 pilot, middle position (I think) on the JJH needle and a 105 main. The main is still slightly rich, but I think it works. That Nibbi needle is just too fat.