Back to this. I let it sit for a bit, because as you know, sometimes
it's better to just walk away for a while. A light bulb might go on.
No light bulbs here.
Here is what I've done recently.
re modified the main nozzle. Thought that maybe the groove wasn't deep/wide
enough. no change.
New head gasket, and level sanded head.New gasket between block and heat shield. no change.
Recleaned all pasages in carb.
New main nozzle and main jet. Set float as per instructions in new seal kit.
New low speed jet. no change.
Bushed the throttle shaft. no chage.
So then, because I started second guessing myself, I took the carb off the 12
again. With some adjusting the 10 runs like a clock. Perfect in my mind.
Put the 10 carb on the 12. Created the same no idle down situation.
One thing I noticed, is that as the engine gets hotter, the problem gets worse.
That's using that cursed carb on either the 10 or 12.
As it sits there rev'g and not idling down as it's supposed to, it will start
racing faster as it heats up.
Now I'm thinking-crack in the carb? as the metal heats and expands it
sucks more air. Make sense? How can that be verified?
I really want to know what's wrong with this carb before I cremate it.
Wow, that does make it puzzling for sure. About the only way I can think of to test for a crack would be to make two plates to cap off both sides of the carb and one plate having a fitting to hook an air line to and put a couple pounds of pressure to it and spray with soapy water. Other then getting an ultrasonic test of it I have no other ideas to test for cracks.