Installed rebuilt "Langdon's Stovebolt" 5200 and two barrel adaptor on 170 with a worked D7 head/Headers. Idles and runs great but stumbles badly when secondary opens. I've been told jetting change could help. I haven't found much literature on jetting changes. I looked in a few repair manuals and the only secondary jet they refer to as "Secondary Idle jet". IDle has nothing to do with the secondary - I think - so is this the secondary main jet?.
There are two jets easily accessed across the top of the carb, the choke side is the primary (Idle?) jet and the opposite is the secondary (idle?) jet according to "the manual".
I looked down the carb at idle, snap to 1/2 throttle and snap to WOT.
> AT idle a litttle gas seen atomizing in venturi area
> AT Snap to 1/2 , The Acc pump and then main gas dump into center venturi feed as engine quickly approached @ 4000RPM
> At snap to WOT, UNLOADED NOT DRIVING, stumbles as gas is dumped into center venturi feed in both barrels, as engine speed slolwly gains, it recovers and races toward 6000 RPM quickly. Under LOAD DRIVING in second it runs well accelerating until second barrel opens then stumbles and slowly picks up RPM until finally winding towards redline.
Does this sound like a jetting change indicated? Runs great with YF 1 barrel and I prudently have made no other changes until I straighten out this carb. Looking forward to 'Quadra-jet' style launch when WOT secondary situation worked out.
Powerband (1K to @ 4K right now).
There are two jets easily accessed across the top of the carb, the choke side is the primary (Idle?) jet and the opposite is the secondary (idle?) jet according to "the manual".
I looked down the carb at idle, snap to 1/2 throttle and snap to WOT.
> AT idle a litttle gas seen atomizing in venturi area
> AT Snap to 1/2 , The Acc pump and then main gas dump into center venturi feed as engine quickly approached @ 4000RPM
> At snap to WOT, UNLOADED NOT DRIVING, stumbles as gas is dumped into center venturi feed in both barrels, as engine speed slolwly gains, it recovers and races toward 6000 RPM quickly. Under LOAD DRIVING in second it runs well accelerating until second barrel opens then stumbles and slowly picks up RPM until finally winding towards redline.
Does this sound like a jetting change indicated? Runs great with YF 1 barrel and I prudently have made no other changes until I straighten out this carb. Looking forward to 'Quadra-jet' style launch when WOT secondary situation worked out.
Powerband (1K to @ 4K right now).
