needing carb help!!

[madwolfcody]

i recently just purchased a 2022 motomax 250 and replaced the stock carb for a nibbi carb currently last night i was running a 130 main get and 40 slow jett bike ran great then today i start the bike up with no problems but at 5000 rpm bike falls on its face and spit and sputters the needle is on the 4th setting and the a/f screw is 2 1/4 turns out im running stock air box / stock exaust im located in the dallas texas area and i have adjusted the valves as well to spec any help would be great.

[Bill Hilly]

That is a huge main for a bike if it's internally stock
Your elevation is around 500 ft. A 110 main if exhaust, and air filter is stock. A 115, or 120 if aftermarket exhaust, and pod filter would be about right.. Your pilot is a little big too if stock.

[XLsior]

is it a rubber boot fit or a gasket flange fit? there might be leak.
As Bill eluded to, it could be over jetted...
might want to try the middle 3rd clip on the needle if the issue is specific to 5000rpm.

[madwolfcody]

https://www.amazon.com/dp/B07PCN9MQW...roduct_details
this is the boot i have.

that is what i thought as well but i tried so many jets yesterday and 130 was the only one that made the bike run good i have ordered inline fuel filters as well just in case idk what else to do tho i can try to move the clip up 1 in the morning and try that

[XLsior]

if you have like some spray degreaser/parts cleaner and spritz around the boot while the bike is running on idle and there is a rev change then the boot is not sealing properly.

Which might get worse around the 5000rpm+ because you were getting air passed the carb....then this becomes a false lean condition which you might have been overcompensating with the jetting.

Have to be certain the carb is installed without leaks before doing any adjustments.

[madwolfcody]

Okay I will try in the morning

[madwolfcody]

And I purchased a 30mm carb should I have gotten the 28mm?

[XLsior]

Megadan has advised the nibbi 30 is a bit to big for easy tuning /temperamental on CG250 engines.

I can't say from experience. But my PE28FL has been pretty forgiving other than the idle which likes to change with the weather, but is easy to adjust on the fly with the side knob.

[madwolfcody]

just ordered this https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
and a nibbi 48mm filter will be here Wednesday hopefully it will work

[XLsior]

Do you have an intake fanged manifold?

[madwolfcody]

I do I have the stock one

[madwolfcody]

pulled the plug this morning and its running very rich like you said i went ahead and pulled carb and reinstalled the stock manifold getting it ready for the new nibbi 28FL carb and pod filter im still trying to figure out how to post pictures on here

[madwolfcody]

heres what it currently looks like

[XLsior]

There is a fairly high probability the idle adjustment knob will hit the bike frame with the straight shot fanged inlet manifold.

you might need an offset type as Nibbi carbs are a bit differently proportioned.

I searched amazon and aliexpress but found it easy on ebay.

https://www.ebay.com/itm/204133107030

Not sure why you didn't just continue trying to tune the Nibbi 30.

If it was running rich then it should of came with leaner jets and starting the needle clip back in the middle.

[madwolfcody]

the nibbi 30mm was giving me issues i tried a 100,105,110,115,145,125, and 130 main jet had a 35 slow jet in it and changed it to a 40 and could not get it to run worth a crab i left the needle in the 3rd clip position i made sure the fuel line was not kinked or clogged fuel was flowing good i had an apollo db-36 and installed a nibbi 28mm on it and it ran good out of the box this one on the other hand has not given me any faith and yes i know about the carb possible touching the frame i had this issue with the nibbi 30mm i think the 28mm will clear the frame better when i receive it today and install i will post picks of the install and let you know about the clearance i appreciate you taking the time out of your day to help me out