Engine stumble followup

OK..

By "feel" there is a little looseness in the throttle valve
bushings in the carb.. we gona look further.

Thanks to all for some great thoughts/solutions.

Can anybody suggest some tests to confirm an intake system
leak that allows excess low DA air to lean the mix when the throttle
valve closes rapidly at high engine RPM?

What clearance should there be in the Throttle Valve bushings?
(if any)

Dave

Can anybody suggest some tests to confirm an intake system
leak that allows excess low DA air to lean the mix when the throttle

Low density altitude air?
Does this mean less than manifold pressure air?
Does this mean the intake manifold air is leaking out or leaking in?

Yes...dense air requiring a richer mixture...

No..... higher thsn MP air pressure..

Leaking into the manifold when the throttle is closed quickly...

Dave

On Sat, 10 Dec 2005 23:51:00 GMT, john smith wrote:

Can anybody suggest some tests to confirm an intake system
leak that allows excess low DA air to lean the mix when the throttle

Low density altitude air?
Does this mean less than manifold pressure air?
Does this mean the intake manifold air is leaking out or leaking in?

Arrrrughhh!

Flew today, -5C as opposed to -8C...

Could not get it to stumble on throt retard.. Rich, lean, VERY lean,
Rt tank,Lt tank, Pump on/off.

I don't know whether to be disappointed or elated.

Looks like I gotta fly it some more...

Dave



On Sat, 10 Dec 2005 13:32:05 -0400, Dave
wrote:

OK..

By "feel" there is a little looseness in the throttle valve
bushings in the carb.. we gona look further.

Thanks to all for some great thoughts/solutions.

Can anybody suggest some tests to confirm an intake system
leak that allows excess low DA air to lean the mix when the throttle
valve closes rapidly at high engine RPM?

What clearance should there be in the Throttle Valve bushings?
(if any)

Dave

Don't panic if you can feel clearance in the throttle shaft bushings.
Any carb with some time on it will have clearance, and it will feel
excessive. I don't of any spec on the allowable clearance, though.
Instead try to compare it with some other engines. Expect maybe .010
inch looseness on a worn shaft.