O320 Carb Problem

[wburnham]

Have an older RV-4 with unfiltered ram air set up. Has a step or stutter as you advance RPM. Slow throttle advance stutter is passing through 1200 RPM, Fast throttle advance stutter is at 900 RPM. Original carb was just replaced with a rebuilt by my local IA and I. It had leakage issues. Both Carbs have had this stutter during throttle advance. The new carb is a bit better, but still has the stutter. IA and I have checked for induction and exhaust leaks. All seems fine. Has any one else noticed this with the unfiltered ram air set up?

[mahlon_r]

If you have a primer, try disconnecting it and capping the engine fitting off. I would also try setting the idle mixture way lean or way rich and see if that helps. Also you might try re-rigging the accelerator pump linkage to change the schedule of how it dumps fuel into the carb. If you look at the throttle shaft you will see that there a re a few holes you can move the linkage too, to change the way the pump discharges relative to the throttle movement.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk."