Hi guys,
I just bought myself a 2000 Road King with about 18000 miles(KM here in Korea that's what I estimate).
I took it to my shop and decided to change all the oil and get some new plugs.
The previous owner obviously had a lot of knowledge and seems like he took care of the bike well, It's super clean and the plugs looked like it was burning normal too. There was nothing abnormal about the bike aside from a regular squeak or two when I come to a complete stop.
When we drained the primary though there were a few flakes on the magnetic bolt thingamajiggy and like three pieces about a little less than a half inch long and flat, and a twelveth of an inch wide. Too big to call flakes and to small to say my tranny is jacked.
Ok. It looks like a couple of the gear teeth might have lost a piece of it.
The guy who looked at it said it's actually not small and asked me if I heard any abnormal noises and I really didnt. aside from the fact when I try to get down to first at about 25 mph with the clutch pulled there were a couple of clickity clacks. (I never heard this with my 09 street bob whe I did the same thing. Only a whine)

What do you guys think? It was like two or three small pieces with the biggest being the measurement I said.

My mechanic says dont worry about it but I wanted to know if anyone else experienced something like this.

 

I would do a complete clutch adjustment with the bike completely cold and see if the clicking on downshifting goes away. If not try adjusting the shift pawl. If still clicking then pull the chain inspection cover and see how tight the chain is. If that is ok, pull the OP cover and see what is happening.

Now don't forget you have 3 sumps on that bike as the trans has it's own oil. If you didn't change the trans oil I would want to see if there was any metal in there.

 

The primary case is NOT your transmission. Any medal on the primary magnetic drain plug is coming from the your compensating sprocket assembly, starter drive gear, clutch basket assembly, or maybe something with the chain tensioner, Not you transmission gears.
Open up your primary and visual inspect all the above items in the primary. Repair as needed.
Do Not down shift into first gear above 3 mph, keep it 2nd. gear and slip the clutch.

 

The trans and primary both have magnetic drain plugs to pick up small pieces of metal, that is what they are there for. However some of your 'bits' do seem rather large!

I would not go so far as to say you shouldn't change down until 3mph, but in every other way I agree with JamesRK. Take a look in there! It will cost you a little oil and a gasket or two to see what is the problem, if any.

 

As the others have stated, the primary is not your transmission. During my oil changes, my transmission oil comes out clean as new, while the primary side is very darkened or discolored (after 5000 miles running Syn3)
From your description, it does sound like you have some gear teeth from either your starter gear (part of the starter clutch assy) or the clutch hub has some teeth missing, which is what your starter gear engages to start the motor.
Fine metal accumulating on the magnetic plug may be more of an indicator of compensator wear. Thinking about it, the starter gear may be steel (magnetic) while the clutch basket is aluminum (non-magnetic). Not sure if the gear is steel or aluminum on the basket.
Pull of the primary and take a look around. I have found that if you wash the primary gasket carefully in a sink and rub it with dishwasher soap and water, you can clean the OEM gasket up and let it air dry and reuse. I am on my 3rd re-use with still no leakage, even after accidentally putting a slight bend in the metal core. My local shop delivered my bike once after pre-paid maintenance oil change, and was the first time it ever leaked. Have distrusted the dealer mechanics ever since.
Good luck on finding the root cause.