Mikuni SBN jet sizes

2kdime

New member
Running a SBN 38mm on a GX390

Considering alcohol

Does anyone know what jet sizes are preferred for such an application?

Couldn't you just go big on them and then tune via the needles?
 

2kdime

New member
Nobody?

How about a step by step of the tuning process for someone who has never had to do it before?

And ways to tell if a bigger or smaller jet is needed?

Thanks
 

Method racing

New member
Hi there did you ever sort the sbn 38 carb out. Also sitting with on. 460 motor. Needle size and pop off pressure and jet sizes to start with. Thanx
 

alvin l nunley

Premium User
I'm not that familiar with that carburetor. I do know it takes about twice as much alcohol as gasoline to burn correctly. Increase the jet size "area" by twice is good for a B and S carb. Remember, not the diameter, but the area. Pi R squared.
 

Method racing

New member
I'm not that familiar with that carburetor. I do know it takes about twice as much alcohol as gasoline to burn correctly. Increase the jet size "area" by twice is good for a B and S carb. Remember, not the diameter, but the area. Pi R squared.
HI I'm running on pump feul. But there are no inv on how to jet it on kart motor. And not a lot of people can help. Bullfrog sells a carb of the shelf that tuned and jetted. But doesn't reply back. And I'm siting in south Africa.
 
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