Found my clutch cable frayed so I bought a new one specific to BMW K100 1984 and on. Watched all the 'how to' videos and installed the cable.

NOTE:
1. I have a custom K-bike with universal clutch and brake levers (no issues with the brakes).
2. I'm using the standard K-Bike Clutch Nipple
3. I did this by drilling out a large enough hole in the universal clutch lever

It's set at exactly three inches in the back, but I had no play in the clutch lever so I backed the clutch bolt out until I had the 5mm play in the clutch lever, but when I turned the bike on it was as though all gears were in Neutral. The bike kept running but there was no gears engaging despite the shift lever clicking into them up or down. So I then rotated then bolt back in until the gears would engage properly, but by the time I get to that stage I'm back to having no play in the lever again. The other issue is that I have lever range of about 10-12mm where the clutch will engage to up or down shift. If I I'm short of the 10-12mm range the clutch won't engage and I can't shift. If I go beyond the 10-12mm range the engine turns off. I understand that it's not ideal that I have custom clutch lever, but I've had this bike for a few years and I've never had this issue before - does ANYONE have some idea what the issue is or how I can go about trying to find a solution? If nothing else, how do I get more range out of my clutch lever so I'm not stuck trying to pull or release it in such a small window range?

Thanks in advance

With three inches(actually 75mm) of inner cable exposed at the lower end of the cable, you adjust the screw on the arm that pushes the clutch rod until it is just touching the rod with the lever on the handlebar all the way out. Then you adjust the cable end at the lever to get the 3-5mm free play.

That is the procedure for the stock bike. With aftermarket levers and who knows what other mods on the bike, I wouldn't be surprised if that doesn't work and a different adjustment must be made