Custom/Hybrid Carb screw compensation for jetting
- Thread starter Pablo
- Start date
- Location
- Harveys Lake PA
Trying to understand your question:
What is the effective range of the screw? (Like as far as how many turns are max from closed/open and not be out of range of the screws adjustment)
Or how much can the screws add as compared to going to the next jet size?
As far as range of screw adjustment, aftermarket carbs may be different, Ed at full spectrum swears anything less than 1/8 turn from closed and 3/4 open from all the way closed is beyond the range of the screw and you need to change the jet size.
Hope that helps?
What is the effective range of the screw? (Like as far as how many turns are max from closed/open and not be out of range of the screws adjustment)
Or how much can the screws add as compared to going to the next jet size?
As far as range of screw adjustment, aftermarket carbs may be different, Ed at full spectrum swears anything less than 1/8 turn from closed and 3/4 open from all the way closed is beyond the range of the screw and you need to change the jet size.
Hope that helps?
Yeah...Ed's words have rung true in my ears. However, I've seen carbs work great at 2 full turns out, but I'm certainly no one to ask on the topic. I'm really wondering how far off on a jet size u can be and still make up the difference with the screws?
- Location
- Hamilton Ontario
I have heard anything over 2 turns needs to be jetted but i have no idea how true that is
The top screw supplements the main circuit. The bottom screw sets low idle only. If I end up 1.5+ turns out on top I will up the main 10# and retest until it is less than 1 out. It is safest to use the largest main jet possible and still be able to peak the rpm with the screw. This means that the screw will be almost closed on a hot day and opened a little more on a cooler one.