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Discussion Starter #1
Quick question for anyone with a stock intake isolator out of their bike, or anyone who knows off hand what the stock size of the intake port is on a stock head? Considering a finbro 27/23mm head to go with my 164 bbk to help her breathe, but im not going to go for a bigger TB.
 

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it's small. the stock butterfly is 24mm and it bottle necks downwards so 21~ sounds correct.

koso butterfly is 34mm and the intake port is 30.5.
 

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ah ok. Contemplating on grabbing a bigger valved finbro head but im not about to drop more coin on an aftermarket TB.
Just open up your stock intake pipe to about 26-27mm and also the spacer to 26-27mm and port match it to the intake port of the head.

Finbro sells the inlet tube that has been mod but cheaper if you have a machine shop or friends that know how to port your inlet tube.

On the gaskets just go down to O'Reilly or auto zone and get a gasket kit and make your own.

good luck and ride safe
 

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Discussion Starter #7
FYI pulled off my stock throttle body and measured the intake tube / isolator / stock head and the port size is EXACTLY 23mm (29/32nds of an inch)


Just open up your stock intake pipe to about 26-27mm and also the spacer to 26-27mm and port match it to the intake port of the head.

Finbro sells the inlet tube that has been mod but cheaper if you have a machine shop or friends that know how to port your inlet tube.

On the gaskets just go down to O'Reilly or auto zone and get a gasket kit and make your own.

good luck and ride safe

Nope..... finbro heads are ported to 24mm... no point to open intake tube bigger than the port. Id rather have a slightly smaller intake tube / isolator and step up to a bigger port than visa versa.
 

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well my head is ported to 30.5mm. If you wanna make power, you might as well go all the way. I mean you saw my results in the other post.
 
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