Dank u wel!

The springs on the advance unit can go weak, which changes the advance curve so that it goes advanced too soon.

Did you try a bigger main jet? Or a bigger intermediate jet? Try two sizes bigger for either one of those and see if there is any difference. At 3K RPM, I think that is pretty close to the start of the main jet. I think I would try 2 sizes bigger on the intermediate first and see what it rides like.

 

The other thing to try is to go 2 sizes smaller on the jet sizes (one jet at a time) and see what it is like. That's how I do it on tuning the S&S's. Also, ride it to exactly where it is acting up and hit the kill switch and coast to the side of the road, then pull the plugs and read them.

 

It runs way to bad to even ride if for a testride so that's not really an option.

It'll bog down really bad, nearly die and then all of the sudden come back to life again...

 

Could be too fat. Try the smaller jets one at a time.

 

If it is in Fact carburetion.
Assuming the Float is set properly, and the Fuel flow is Good...ie no inline fuel filter. A real exhaust, with a 295/170-175 jetting setup, No air cleaner, [or K&N] and no Accelerator pump... The accelerator pump is to be set after the carb is tuned.
If it don't run...something else is wrong...

Shovelhead ??? Probably has an Intake leak...like someone mixed and matched oring/Rubberband Components..Not the Carburetors' fault.

 

Tried leaner jets as well but it's not to fat because when I strangle the carb is runs much better.

No intake leak either: brand new proper rubber seals I've installed myself.

 

I'm still thinking it is carb related. You could confirm the spark is good by looking at the timing with a timing light when it is acting up, but it sounds like carb issues to me. You might try a different carb. I would guess that shovel carbs are not real common over there, but if you can find something off a mild Evo that will bolt up to the same manifold, it might be worth a try.

My old shovel went to Holland. A bunch of Dutch guys went around the US in the late 80's buying up older bikes and shipping them home for big profit. Price negotiations were very interesting. It was like I could see how their minds worked. They were trying to work me over until they found out I was Dutch also, then the deal was done as there was no point in negotiating further.

If you run across a 1979 FLH Classic cream and tan, it might have been mine.

 

Inline filter?? I suspect fuel flow
O-ring or Rubberband?
Which Clamps?

 

Rubberbands from James with the double screw-type clamps on it.

Since I must confess it's strange that it works much better when I strangle the carb I will go up on the slowjet as that does seem logical although I can't imagine why it would need such a big slowjet...

Come to think of it: my turbo'd bike which is also in a super E did the same when the slow was to small but obviously didn't pop in the carb because of the turbo.

It did however stumble in the same fashion so...?

 

IDK what a double screw type clamp is
Note that a Rubberband intake works best [actually requires] with a Split clamp..ala the Stocker with a "space in the middle, such that it does Not clamp the Middle like an o-ring clamp...
I still think intake leak...