Well I have searched the archives, finally had to register and post a new one. Sorry for the long post, just had to include as many details as I could think of.
I just bought a 1990 XR80, stock. I'd like to fix it up for the kids, not a racer, just a backyard bike. It has been well used, but runs, does not smoke, starts on first kick. Since it has been stored in a barn for some unknown period of time, I pulled the carb and dissassembled it, used 2 cans of carb cleaner and compressed air to clean out the rust and crud. I made sure all the tiny holes were clear, did not use any wires or picks on the orfices. Also installed a new O ring between the carb and the manifold. The large needle valve and other jets look pretty good to me, no scars or grooves. I cleaned the wire mesh filter and installed a new foam filter, and a new spark plug.
After installing the carb back on the bike, it started fairly quickly. My local Honda dealer was nice enough to photocopy the section from the Honda Manual for servicing and adjusting the carb. I rode the bike around the yard to warm it up before fine tuning the idle and air jets. I backed the air jet out 1 1/2 - 1 3/4 as described in the manual, and after tweeking it a bit, I can get it to take the gas when I chop the throttle. The problem is that I can't get it to idle. I can turn the idle screw all the way in unti it stops and it still will not idle, no change in rpm from full in to full out. I can just crack the throttle grip and make it idle, but it is not smooth. I can't figure out what is happening. The spark is a crackling blue. The nut where the the cable connects to the carb is tight, the gasket under the nut is in good shape. I feel like I am close to getting it to run right, just missing something. After it is hot, I twist the throttle about 1/8th of the range and it fires up on first kick.
Any help is appreciated.