MJD

My Feedback: (1)

Indeed - nowhere in this thread is there mention of richening the low end so much it showed the symptoms of being too rich instead of too lean. It only takes a minute to try this out at the field! If you haven't gone that direction yet then you need to verify the response to eliminate variables and doubt (and endless theorizing).

I find it a lot easier to home in on the right mixture from the rich side, it is easier to read the behaviour and might eliminate those starting woes. 50 seconds cold cranking? OUCH - I shut the starter off after 3-4 seconds and figure out the fuel situation. I hate seeing a starter used to pump fuel to a dry engine. I'd rather start an engine with a wet crankcase then pinch the line to clear it out, at least that way I get the sense there is some lube in there.

RC_Fanatic

My Feedback: (1)

I hadn't tried adjusting the idle needle as, once the engine gets out of this strange mode, all indications are that the idle is spot on. Also, the engine is cowled in and it is difficult to access the idle needle. On the two previous 46AX's, and on this one until this fall (it did not exhibit this behavior last winter) I've not needed to adjust the idle mixture once the engine is broken in. However, when I pull the cowl off to check everything else, I will put in a larger hole to access the idle needle.

MJD, I prime the engine manually before applying the starter so I know the fuel is in the engine and the lines are full. It won't even fire on the prime.

We're heading to the in-laws for Thanksgiving and I'm laid up with a cold today so will check it out after We get back. Stay tuned!

blw

My Feedback: (3)

The low speed needle valve is usually the most important one on an engine when it comes to being tuned to run right.

Most people tap a small hole in the cowl to slip in a small screwdriver to adjust the low speed needle.

Mr Cox

Yes, on a twin needle design it covers the whole midrange, and can even interfere with the full throttle setting.
So quite different compared to the operational range of an airbleed screw.

MJD

My Feedback: (1)

No kidding? No wonder you're scratching your head.

Turk1

RC_Fanatic

My Feedback: (1)

Problem solved, but still a mystery remains. []

I haven't been out for a while bad cold, cold weather, rain, visitors... Anyways, I pulled the cowl off and checked all the lines nothing there. I chopped a hole in the cowl to get at the low-speed needle when the cowl was on. On a hunch, I looked in the carb with the throttle wide open, and compared it to the old 46AX, and one that was NIB. The current one had virtually no gap between the spray bar and the idle needle, but the others had a small (tiny) but visible gap. Using a feeler gauge, I adjusted the current one to match the others (opening ~ 1/2 turn) and re-assembled the plane. For safety, I also richened the main needle.

When I finally got out to the field, I primed 3 flips, connected the glow ignitor and the engine started on the fifth flip with the chicken stick! After the engine warmed up a bit, I leaned out the main needle at WOT to about 200 rpm below max. The needle is now about 1/4 turn richer (open)from where it was before. I'm not sure about the rpm as compared to before as I had not noted the rpm with this prop before. The low was almost right as set. I tried tweaking it, but I could not adjust it to get as quick a rev-up as I had before. I fiddled with both settings but could not improve it any. It is acceptable as is. However, now the engine when warm will not start with a flip of the spinner as it did before. []

Questions remaining are
1) Why did I have to richen the main needle when opening the idle should have called for leaning it out?
2) Why does it not start when warm as easily as it did before?
3) Why can't I get the same responsiveness as before?

kerwin50

On the low end I adjust it in small increments to just where it no longer hesitates, startb rich and go lean.
With cooler temps my engines run a little leaner so I have to readjust them