gx390 jet sizes

747

New member
I have a pod filter and header on my 390, with a stock carb. I jetted it to 1/16 but its super rich. What size do yall recommend jetting the carb to?
 

Kart43

Active member
You need to buy drill bit set that goes a whole lot smaller than 1/16" which is .0625" you need to be some where around .036-.040"
 

747

New member

Kart43

Active member
On 89 octane gasoline the numbers provided are a starting point for you and yes that is the main, if you hogged the pilot out to those numbers you will have a poor runner for sure.
 

WinstonSmith

New member
I have a pod filter and header on my 390, with a stock carb. I jetted it to 1/16 but its super rich. What size do yall recommend jetting the carb to?
Yall?

Here is a trick for you.
Do you have a drill press ( yes is good no is bad )
Put the jet in the press and bit in a small vice.
Set up here is critical you want to straight, square and on centre before the bit bites the brass.


By spinning the work and not the tool you will make a straighter rounder hole.
When your drill job is ugly your jet might not flow the fuel you are expecting and you can not consistently produce jets for your kit that deliver the right amount of fuel for temperature, track and elevation.

There are also some aftermarket adjustable main jets that might be a better choice so you can tune on the fly.
 
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