Need insight

Predminibike

New member
I have a big valve predator 32mm intake 28mm 36lb valve springs titanium keepers need racing cut to length pushrods need racing 252 cam 26mm nibbi racing carb I have another bike with same set up except the only difference is it has 26lb valve springs and stock head and it's smokes the bike with the big valve head so what's the advantage of the big valves
 

Jc53

Premium User
The big valve head will need a larger carb and higher rpm to be of any benefit. Research port velocity and you'll see sometimes a smaller port & valve makes more power when it's matched to the rest of the build
 

Predminibike

New member
Thanks for the info jc53 I have a 28mm on there now with a 125 jet and it still falls on its face at wide open throttle what size carb do you suggest
 
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