Nibbi PEZ28 on 2024 CSC TT250

[bigdano711]

I'm starting to think Nibbi is junk that was hyped up by people who don't know any better. Guilty as charged.


Again, I follow those who are more knowledgeable than me. I saw Megadan try the Nibbi, got it going ok, but ended up with the Mikuni clone. You can monkey with the stock carb, but I prefer a carb with an air/fuel mixture screw I can see, a pilot I can change and a needle that adjusts in both directions. Plus, the Mikuni clones are inexpensive.

[XLsior]

I'll agree in that a nibbi PE28/FL for me has been a fidgety unit. However my CG250 isn't exactly stock either.


I think the needle profile could be an Achilles heel to tuning as Bigdano has eluded too.


Buying a various taper needle kit isn't expensive...But after you play with jet kits and then throw in needle kits its all bit of a ball ache...


I have PZ30B pumper but the issue being the A/F is underneath and practically inaccessible when installed so I got the PE28FL instead...


I might look at VM26 clones, but at this stage I'm thinking the XL185/CG250 project has served its purpose and putting all funds towards a MT450 is money better saved and spent at this stage of my 2 wheel adventures...

[ProDigit]

The people that usually buy a nibbi carburetor, always end up on the forums and Facebook threads complaining about rough idle, throttle cable not fitting, bike not running right.

Then it turns out that they buy a carburetor that's either one or two sizes too big, thinking they can get more performance out of their vehicles.
They probably saw some YouTuber installing a nibby carb, like Motocheeze, thinking that that was the best carburetor they could install. In the case of Motocheeze, he was just experimenting with Nibbi versus Mikuni clone.

I've always said that a Mikuni carburetor is just as good as a nibbi, if not better considering the price.
Many people have said the nibbi will last longer, but they don't know that the nibbi is also Chinese, it has a polished internals witch has proven not to add anything to performance at all, and it just looks nicer, but in many cases has clearance issues with the frame as well. Another thing they don't think about is that the Mikuni clone carburetors are probably going to outlast the bike, for as long as you regularly use it. Most bikes won't last 30,000 to 40,000 mi, 7 years maximum, I see no reason why these carburetors won't be able to do at least four to five years and 50,000 mi.

The only ones that I probably would be cautious of, are the clone carburetors with a pump built in.

Those pumping membranes are known to disintegrate over time, not only from Chinese carburetors, but also Suzuki or even Honda carburetors.

[bigdano711]

I think Nibbi's biggest claim to fame on that PE28FL is the big red idle adjustment knob. That thing is sweet and was a great idea. I fought some handlebar turn, throttle increase issues. I fought that needle. The jets weren't too big of a fight. I actually have it running the best it ever has on my bike, but feels like it still just ain't right.


Here's the weirdest thing. I knew I was fat on my main jet and was slowly coming down. Now, the bike just did NOT want to start without choke, no matter how hot it is outside, and that just ain't right. Well, I came down to my smallest size main jet, 100, and suddenly she wants to fire right off, no choke, on a warm day.


Now, I thought for sure the main jet and the idle circuit were so far away from each other, one cannot possibly affect the other. That's about the time I decided to go with the Mikuni clone.

[Thumper]

This is for the PE28 (Keihin clones). There must be one for the Mikuni clones:

https://www.chinariders.net/showpost...80&postcount=6

[superjocko]

I've been perfectly happy with my natural aluminum bodied Nibbi PE28FL after a little jet tuning to get it dialed in. That said, I wouldn't mind trying a carb with an accelerator pump just to see if it would help with lofting the front wheel over trail obstacles more easily. I'm inclined to think that the not-so-snappy bottom end very well may be more related to the immense flywheel mass (relatively speaking) this engine has more than anything else though. These things are never going to have the low end snap of a 250F motocross or enduro bike no matter what you do. Mine fuels cleanly throughout the range of RPM, but snappy off the very bottom it ain't.

[Sdmfjon]

Originally Posted by superjocko

I've been perfectly happy with my natural aluminum bodied Nibbi PE28FL after a little jet tuning to get it dialed in. That said, I wouldn't mind trying a carb with an accelerator pump just to see if it would help with lofting the front wheel over trail obstacles more easily. I'm inclined to think that the not-so-snappy bottom end very well may be more related to the immense flywheel mass (relatively speaking) this engine has more than anything else though. These things are never going to have the low end snap of a 250F motocross or enduro bike no matter what you do. Mine fuels cleanly throughout the range of RPM, but snappy off the very bottom it ain't.

In the end I determined the motor in its stock form cannot run the Nibbi carb. Having that motocult stage 3 with the bigger cylinder and the cam makes the difference. Motocult claims it takes a stock engine from 14.5hp to 20hp. In terms of air movement that is a huge increase.

I almost want to try Nibbi's PE26fl, I bet that bore is similar to the stock Keima carburetor. Yeah it won't "top out bro" but I bet the drivability would be great n

[Sdmfjon]

Originally Posted by bigdano711

Now, I thought for sure the main jet and the idle circuit were so far away from each other, one cannot possibly affect the other. That's about the time I decided to go with the Mikuni clone.

Try changing the needle a notch. It effects the entire throttle range. So much so that changing a notch on the needle forced me to re adjust the air/fuel screw at least 1 turn.

[ughmas]

Originally Posted by Sdmfjon

Try changing the needle a notch. It effects the entire throttle range. So much so that changing a notch on the needle forced me to re adjust the air/fuel screw at least 1 turn.

want to thank everyone for all the posts on this thread, I know its mainly about the PEZ28 but reading everyone's data and thoughts made me get my PE28FL back out and start from scratch. The needle is the one thing I did not change and it turns out everyone here is correct, the nibbi needle is way smaller and lets in a lot more fuel - went back to stock 40 pilot jet and 1.5 turns out with needle Dropped to 2 Position (2nd from the top, stock is 3) and started tuning from there. The needle at 2 made all the difference - so far ended up with 40 pilot, screw 1.75 turns out. My bike can now pick up the front wheel off idle with very little effort which it has NEVER been able to do since i've owned it. (and thats WITH going to a 49 tooth sprocket from the 50 recently) Can crack the throttle pretty good with no bogging



going to test a bit more, but midrange feels great, just need to check and tune main jet/high end now as I was just going around my yard.



I have a pod filter, exhaust, and emissions deleted.

[Airhead]

Originally Posted by Sdmfjon

Zero to full throttle rips on the stock carburetor. Barely any hesitation. Comes right back to idle.

My tt250 has never run this well. Maybe my answer is to just leave the stock carb on lol.

Stock carb.
35 idle jet
Main jet 112
Needle position 4
Fuel screw 2 3/4 turns out.

Here's a video.

4 seconds into your video shows the stock carb vent(?) capped off. Is that correct? If so, why? This is a very slow learning process for me. Thanks to everyone for all the great comments.