06 Road King Classice shuts off when in 4th gear beloe 50mph

It's the low oil pressure warning lamp. It's suppose to come on at every start up. It will stay on for a couple seconds after the engine starts. This is normal.

Your bike to shutting off because the sensor is telling it that I don't know if you have eradicator, Dorothea have a loyal oil oil oil. There is a sensor that is telling your motorcycle to shut off because there is some sort of problem either. The sensor is bad or you have a problem somewhere. If your bike runs will ruin the engine you need to call a Harley dealer and asked them or go online like you are now on as somebody who has a bike like yours, but it sounds like to me that you have an issue with one of your sensors and the bike you shutting off to avoid further damage

I just answered this question a couple seconds ago find out what sensors are on that motorcycle that would shut it off. I overheating, low oil, etc., etc.

32 ounces (946 ml) of Harley-Davidson FORMULA+
TRANSMISSION AND PRIMARY CHAINCASE
LUBRICANT

The engine light coming on and going off is normal. It's part of the start up sequence. If the light goes off then comes back on then goes off again it means you have a " historic " code. Meaning ans event that happened in the past. If the light stays on and won't shut off then you have a " current " code. meaning it's happening as you are sitting there.

I’m happy to assist further over the phone at https://www.6ya.com/expert/robert_5bac37c3cb991fdb

find web site for Harleys or a site with Harley Clubs lots out there.

Check for waht DTC's are set. Likley the IAC is having problems.

Have you checked with HD to see if yours is part of the Fuel Pump recall?

manual or auto

For valve train noise try these:
1. Low oil pressure caused by oil feed pump not functioning
properly or oil passages obstructed.
2. Faulty hydraulic lifter(s).
3. Bent push rod(s).
4. Incorrect push rod length.
5. Rocker arm binding on shaft.
6. Valve sticking in guide.
7. Chain tensioning spring or shoe worn.
8. Cam(s), cam gear(s) or cam bushing(s) worn.
9. Cam timing incorrect.

If it is a bottom end knock, an engine tear down may be in order.