Thanks Bill. Well it's a shocker of a day today, gale force winds and rain coming in sideways, but as there was a lull I sneaked out to synch the carbs. To start with I was gonna follow the instructions in the factory manual, i.e., tune each cylinder one at a time with the spark plug disconnected on the other cylinder, but the bike didn't like that and wouldn't idle on just one. Hmmnn. I probably should have gotten it up to operating temp, but decided not to worry about that, I set the mixture screws at 1 and 1/4 turns out on each carb, then removed them both.
I installed a new OEM throttle cable when I put the bike back together, so using the slack adjuster I wound it out so that I could use a 1/4" drill bit as a feeler gauge. I then took the slack out of each throttle cable at the carb top, then gave each 1mm of slop as per the good book. I then used each throttle cable so that the 1/4" drill bit was a slight drag under the carb slide on each carb. All good.
I fired it up again, and...... it ran like sh1t. Turns out the left cylinder had been missing and only firing irregularly until I gave it some throttle and it cleared, and began firing regularly. That makes sense to me because when I first fired it up before I started tinkering with it, it was running way better. I can see that each carb is getting fuel, so I'm gonna assume that the plug on #1 is fouling, whether it's from a weak spark or a rich mixture, or possibly both.
I've learned a lot from the FB T500 forums, from guys like Geoff and Paul Caurbot in Britain, the early T500's ran 150 main jets and 30 pilots, whereas from around 1973 they went to 97.5 mains. I bought a rebuild kit for my carbs and they had 150 mains, (and 30 pilots) and interestingly the old ones that came out were 150's as well, so I, being a T500 noob, assumed all was well, but maybe not? Or maybe the points ignition just isn't up to the job?
No biggie, I'd rather it was too rich than too lean, so when I can I'll take it for a decent ride and see whether it comes good when I have the opportunity to blow the cobwebs out. It could just be that running premix as I still am, with plenty of oil getting thru now that the oil pump is working again, plus the oil that I squirted everywhere when I reassembled the engine is just too much for the ignition to cope with? I suppose I could always buy an electronic ignition, I wonder if Dyna make one for a T500? A nice fat blue spark would be nice........