I am almost finished completely rebuilding my 85 K100. Took almost 2 years.

I got it to startup and run, but the idle is very low, even when warmed up. It also feels like I'm pulling a trailer behind me with how sluggish it is. When I go hard on the throttle it takes a beat to pick up but only revs a few thousand higher and then usually dies a few seconds later.

Replaced all the injectors and spark plugs. Only cleaned the throttle body - did not disassemble of touch any of the tunings. So I don't think it's that or the throttle position sensor, clicks as soon as there is any pressure on the throttle. Also put some water on all the airways and didn't see any leaks.

I think it's the mass airflow meter. When I took it off, I was dumb and thought I was turning a mounting bolt, but really it was the adjuster. So It's nowhere near factory settings. When I went to mess with it just now it was cranked almost all the way loose. I figured I couldn't make it worse, so I tightened it hoping to increase the idle and throttle response. It only got worse (which at least proves it's part of the problem, or is at least it is now). Barely goes above 3k rpm at full throttle and takes a second or two to drop after release.

Is there anyway to tune the airflow sensor without an expensive CO meter? Doesn't need to be perfect, just working. And are there any other factors I should consider?

BendK100 wrote:Is there anyway to tune the airflow sensor without an expensive CO meter?

To find a CO meter, check with NAPA, AutoZone or Advance. They often loan tools and gauges with only a credit card security deposit refundable on return.

With the bike warmed up and idling at 1000 Rpm press the green starter button if the mixture the idle should remain the same or increase slightly. If it increases significantly the mixture is lean if it decreases significantly the mixture is rich. If you can't access a exhaust gas analyser look up the lean drop method and follow the instructions. Next time I have one of the K Kronies Bricks with an out of whack mixture I'm thinking it might be possible to tune it by checking and adjusting using the green button. When adjusting the mixture use small adjustments and allow it to settle between adjustments.
Regards Martin.

Have you check the coils to see if they are good? '85 coils are known to be defective over time...   $0.02

Sounds like you need a new fuel filter to me.

One and half turns from bottom is a good starting point. Gently screw it down until it bottoms.
Regards Martin.

The idle air bypass screw in the AFM wouldn't affect things as much as you describe. 
I'm with RickG - replace the fuel filter - even a new one will block quickly if the tank isn't clean. Also check the in-tank hoses for splits. Sounds like a fuel starvation problem, which is common enough and easy to fix.

I found a leak in the tank hose by viewing the lines with the fuel level low and cap open. It was a pin hole leak that only spurted when opening the throttle and fuel pressure raising. It was a bugger to discover it after trying so many other things.

To be honest I would replace everything inside the tank, also the electrical plug connector is a known weak point, front left of tank. So too is the non return valve. You would not be the first to have conencted the fuel lines the wrong way round so check them too.

So you replaced plugs etc, what plugs? Have they bobbins?

BendK100 wrote: Also put some water on all the airways and didn't see any leaks.

The way to find intake air leaks is to have the engine idling then carefully direct a spray of propane or volatile carb cleaner around each intake and at the z-hose connecting the crankcase to the air box near the throttle switch. If you hear the revs change, that component is leaking.

There are lots of good suggestions here.

- I went to ever auto store in Denver and none had a CO analyzer for rent. I bought a Bacharach Monoxor II Electronic Gas Analyzer of ebay, but the exhaust tops it out so it has been no use. I've been riding around my neighborhood with a hex key sticking out of the intake and tweaking it every 10 minutes. Has helped a lot but still runs sluggish and I occasionally get overload error reports for the ignition output in my M-Unit. That leads me to believe it may be the coils. When I bought it, it had one original and one aftermarket coil.

- I thoroughly cleaned the tank before repainting and replaced the fuel filter and all the lines, so I don't believe that would be the issue, but I'll ket it on the list just in case. Still has the electric plug connector I bought it with, so that is also suspect I guess. However, it backfires a bit while idling (shot a little flame once); so I would assume it's running rich instead of being starved.

BendK100 wrote:However, it backfires a bit while idling (shot a little flame once); so I would assume it's running rich instead of being starved.

A lean mixture can cause backfiring.

With the bike warm and idling at around 1000 RPM press the green  button the revs should stay the same or rise very slightly. If they rise significantly the mixture is lean if the revs drop it's rich. You don't need a exhaust gas analyser just look up the "Lean Drop Method".
Regards Martin.

Unfortunately I no longer have a green button. It’s a complete rebuild with custom wiring and buttons. First press of my new ignition button turns on the fuel pump then holding it down fires the starter motor and rest of the ignition system. Another press and it turns off.

The ignition overload and short circuit warnings I’m getting now are making me suspect the coils more. I order some replacements from Holland. I called my local K bike shop and they said they bought out all of Bosche’s stock a few years back and they are all gone now. So it’s a hassle finding them now.

BendK100 wrote:The ignition overload and short circuit warnings I’m getting now are making me suspect the coils more.

Have you tested the resistance at the coil terminals? There is a guide to testing coils on the Tech Page within a document titled Troubleshooting the EFI.