‘79 engine, 750cc big bore just installed, stock cam, HHB CDI charging and ignition kit, straight pipes, velocity stacks with foam inserts.
At 4450ft in elevation and started jetting at:
Needle jet- 159 P-6
Needle- 6F9
Slide- 2.0
Air jets taken out
Main- 175
Pilot- 22.5
A/F screw- 1.25 turn out
Needle clip- 3 from top
Seemed rich as hell, plugs immediately covered in soot. Idle seemed fine, air screw caused stumbling both ways so I think I’m close there but anywhere 1/4-3/4 throttle caused major missing/stumbling.
Main- 160
Pilot- 20
A/F- .75 out
Clip- 1 from top
Worked my way down to these numbers and the 1/4-3/4 throttle cleaned up quite well. My concern is: plugs are still immediately covered in soot. Do these jet numbers seem reasonable for my elevation of 4450ft? I’m kind of worried my ignition isn’t working well enough which is why plugs are black? I have no evidence to support that. All testing of the ignition seem to be in good order. Is my pilot too rich and that’s what I’m seeing? Would really appreciate any input. All components are brand new. It’s a new build. I’m diligent when it comes to the details but starting to get nervous and don’t want to burn this new top end up. Thanks.
At 4450ft in elevation and started jetting at:
Needle jet- 159 P-6
Needle- 6F9
Slide- 2.0
Air jets taken out
Main- 175
Pilot- 22.5
A/F screw- 1.25 turn out
Needle clip- 3 from top
Seemed rich as hell, plugs immediately covered in soot. Idle seemed fine, air screw caused stumbling both ways so I think I’m close there but anywhere 1/4-3/4 throttle caused major missing/stumbling.
Main- 160
Pilot- 20
A/F- .75 out
Clip- 1 from top
Worked my way down to these numbers and the 1/4-3/4 throttle cleaned up quite well. My concern is: plugs are still immediately covered in soot. Do these jet numbers seem reasonable for my elevation of 4450ft? I’m kind of worried my ignition isn’t working well enough which is why plugs are black? I have no evidence to support that. All testing of the ignition seem to be in good order. Is my pilot too rich and that’s what I’m seeing? Would really appreciate any input. All components are brand new. It’s a new build. I’m diligent when it comes to the details but starting to get nervous and don’t want to burn this new top end up. Thanks.
