So,
I fixed the charging system on my Nighthawk 750 that I'd been asking aboutNext in line was a rebuild of the carbs. The bike would idle rough, and choke out when throttled. Pulling the plugs, they were all wet and blacked up with carbon: the bike was getting too much fuel. After monkeying around and avoiding it, I finally pulled the carbs off. I bought a rebuild kit, tore them down, cleaned them in an ultrasonic cleaner with some simple green, and burned off anything leftover with carb cleaner. They reassembled easily enough.
When putting them back together, I noted that the pilot screws provided in the rebuild kit were radically different in design from those that had been on the bike. The ones on the bike had a flange that could be adjusted by hand easily, and those in the rebuild kit had a keyed surface that clearly interfaced with a specific wrench. With a shrug, I reassembled the carbs with the old pilot screws, thinking that doing so would make for easier adjustments. After getting the front bracket back onto the carburetor assembly, I noticed that the pilot screws would get stuck against the bracket. Eager as I was to hear the bike turn over with fresh carbs, I shrugged and passed over that realization. ONWARD! To assembly! Let's hear this baby roar!
I reattached & reassembled everything, and the bike started right up. After a few minutes warming up, I was able to get the idle to smooth out with the throttle stop screw. The bike ran beautifully. A very steady, solid idle, no backfires (it used to do that after releasing the throttle, if it didn't choke out during throttle), etc. I was happy as could be...
When trying to trim out the idle on each carb/cylinder, I found that I couldn't turn the pilot screws without banging into the bracket. Since each step was a 1/2 turn, I figured that maybe if I just forced the pilot screw past the bracket once, I'd be able to get everything set and just move on with my life. The #2 carb pilot screw promptly sheared off right at the carb body. As always, there's two ways to do things: the right way, and again.
I've attached two photos. One is of the sheared pilot screw, and the other demonstrates the interference of the pilot screws with the front bracket.
So, what is going on here? Obviously, I should have installed the replacement pilot screws. But, why are the original pilot screws shaped in a fashion that causes them to get bound up like that? Are those from a different bike?
Next, what should I do about the sheared off pilot screw? I can try to drill it out with an Easy Out, but if that goes wrong, I'll have to buy a new carb body. Is this a must fix problem? The pilot screws are currently set to the manual standard of 2 & 5/8ths turns out from the bottom, plus another half turn to begin adjustment. Do these run normally lean? Normally rich? The process to set the idle suggests to me that the bike runs normally lean, as I back the pilot screws out progressively, which I think lets more fuel flow. Anyway, some guidance would be much appreciated.
