Flat Spot when adding Power

Ted called me this morning to say that he received my carb. After a quick look, he said that it was very dirty and worn. The throttle shaft seals were in bad shape which I expect will explain my flat spot issues. He will report more next week when he really gets it torn to pieces.
 
Jack's idle adjustment comments were most interesting.. and currently greek to me.
Have to think long and hard about that technique and why it works.

Waiting for your further reports from the carb shop.
 
My carb is on it's way back to me. The needle and seat were replaced, the throttle shaft bushing and seals were shot, the economizer was repaired and Ted said that it was very dirty and pretty much everything was leaking. He also changed the float.

I'm very interested to see how this changes things. I'm confident that it will solve my flat spot, but not too sure about the RPM loss....

While my bird was out of commission I replaced all of the old oil and fuel hose firewall forward. It does look pretty now at least.
 
blimpy said:
Jack's idle adjustment comments were most interesting.. and currently greek to me.
Have to think long and hard about that technique and why it works.
Click to expand...
About that idle mixture setting procedure:
To get the engine to start and run when it is cold the idle mixture needs to be slightly rich. So when it is warm it will idle a bit slower that peek. When you pull the mixture to idle cut off the engine will speed up as the mixture first gets leaner and then quit when it is too lean. If it does not speed up the mixture was already at or past peek and you will have problems keeping it running when starting cold, if it speeds up a bunch or takes very much time to speed up there was too much fuel to start with and you need to lean it out a bit or it will idle rough on a hot day.
 
So I finally got my bird up in the air today after the carb overhaul from Ted ($836 including shipping). It definitely started and idles smoother. When warm the mixture seemed stable (before it would run very rich when how on the ground). Ted said from the look of the inside of the carb, it had been running very rich. Took it up for a flight and seemed to run good. I'm still however, getting a bit of a flat spot around 1200 rpm. On Ted's advise I'm going to play around with the idle mixture a bit more to see if I can make that go away.

I got the rpm drop on takeoff right at liftoff speed again of 100rpm or so. The manifold pressure did not change which made me think it was something to do with the prop 'shifting' to a coarser pitch. I spoke to Kent Tarver today and he confirmed that a 100rpm drop at about 60mph is what they have seen with their props. I guess I'm a little confused as to why it just started doing this, but it sounds like it is acting like is should. No change in manifold pressure when it does this would seem to eliminate any sort of problem with the engine and with my shiny new carb that is eliminated as a problem.
 
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