New guy from Clearwater FL

[CRGkx125ivan]

Hello everyone, I recently bought a 2009 CRG kx125 that has been stoked to 149cc.
It currently has a Keihin pwm carburetor.
The track I want to take it to asked me to replace the k&not filter and install an air box.do I need to change the jet? What size? Thanks in advance.

 

[Hellion]

..to the forum, new fella!

I'm sure the resident wise men will weigh in on your inquiry soon enough.
I would if I knew what kind of kart it is.

Once again, welcome.

 

[chancer]

Does it currently run good with the k&n? If so get a good plug read with the K&n. Then put on the stock box, and do a plug read. That should tell you if you need a different Jet or not.

There is no rule of thumb. Like Go 1 size smaller or whatever, You just gotta do what the engine is telling you to do.

 

[landuse]

Welcome. I would put the box on and see how it runs

 

[CRGkx125ivan]

Does it currently run good with the k&n? If so get a good plug read with the K&n. Then put on the stock box, and do a plug read. That should tell you if you need a different Jet or not.

There is no rule of thumb. Like Go 1 size smaller or whatever, You just gotta do what the engine is telling you to do.

Thanks for the advice. Do I use a different spark plug each time? Basically I just bought it with the k&n and now I have to put the intake box back on by the kart track rules. I read online that it should have a #175 jet but I haven't taken the existing jet out yet to see what it is.
I'm going to try what you said and go from there.

---------- Post added at 06:03 PM ---------- Previous post was at 06:01 PM ----------

Does it currently run good with the k&n? If so get a good plug read with the K&n. Then put on the stock box, and do a plug read. That should tell you if you need a different Jet or not.

There is no rule of thumb. Like Go 1 size smaller or whatever, You just gotta do what the engine is telling you to do.

Thanks for the advice, I have only started it but haven't actually put load on it yet. Planning on taking it to the track soon but I wanted to correct this issue first but it looks like I'm going to have to figure it out at the track.

 

[DirtyDamage]

So, K&N style filters are typically higher flowing, however, if it's a racing engine the stock jet should be larger. To be safe, i would get a smaller jet, even if its not needed. In my honest opinion I would think you'd just need to lean it out a bit however(do plug readings just to verify).

If this is your first time racing, i suggest an extra set of pants, it may not sound fast but 60+ in a cart thats an inch off the ground will throw you for a loop, this is coming from personal experience...remember a helmet and stay safe!