Importance of carb/port matching?

Okierider · 05-25-2022, 10:44 PM

Hey y’all. I was playing with my sons 125 and learning (a lot) about carbs and tuning when I decided to take the intake ‘manifold’ off and check port size.
Bike has a 26mm carb. The intake manifold is 26mm at both ends. The gasket on the head intake port was 26mm but the port itself is 28.
So, to me (with an FI v8 background) I need a 28mm carb and intake manifold to match the port.
It’s my understanding that carbs are different though.
I already planned on getting a real Mikuni 26 to replace the China clone on the bike. It’s in my summit racing cart just waiting, and I’m tracking down a new intake because the bolt pattern for the Chinese model is different from the genuine article.
So should I stick with a 26mm or bump it and the manifold up to 28? Assuming all is otherwise stock though, knowing me, it won’t stay that way for long, if I don’t just say screw it and swap a 190 in lol

4T_Goblin · 05-26-2022, 06:57 AM

I'm wearing the vm22-133 on my 125cc. I have the X-Pro Boom Vader Grom clone.
I did absolutely zero port matching and it runs tippy top.
These bikes are not performance monsters.
Research leads me to believe that even a VM20 would suffice for the 125, and that the vm22 is good for up to 14/150

05-25-2022, 10:44 PM	#1
Okierider Join Date: Mar 2022 Posts: 254	Importance of carb/port matching? Hey y’all. I was playing with my sons 125 and learning (a lot) about carbs and tuning when I decided to take the intake ‘manifold’ off and check port size. Bike has a 26mm carb. The intake manifold is 26mm at both ends. The gasket on the head intake port was 26mm but the port itself is 28. So, to me (with an FI v8 background) I need a 28mm carb and intake manifold to match the port. It’s my understanding that carbs are different though. I already planned on getting a real Mikuni 26 to replace the China clone on the bike. It’s in my summit racing cart just waiting, and I’m tracking down a new intake because the bolt pattern for the Chinese model is different from the genuine article. So should I stick with a 26mm or bump it and the manifold up to 28? Assuming all is otherwise stock though, knowing me, it won’t stay that way for long, if I don’t just say screw it and swap a 190 in lol __________________ 2022 X-Pro Templar X 250 “Rocinante” 2022 X-Pro Bolt 125cc “Dapple” 2022 Royal Enfield Interceptor 650 “Traveller” 2023 Royal Enfield Classic 350 “Trigger”
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05-26-2022, 06:57 AM	#2
4T_Goblin Join Date: Jun 2021 Posts: 239	I'm wearing the vm22-133 on my 125cc. I have the X-Pro Boom Vader Grom clone. I did absolutely zero port matching and it runs tippy top. These bikes are not performance monsters. Research leads me to believe that even a VM20 would suffice for the 125, and that the vm22 is good for up to 14/150 __________________ 2020 Vader X-Pro X-7 2019 Kawasaki Ninja ex400 2022 Lifan KPX 250
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