Overhauled Carbs VM28SC - Z1A issues

To chime in here, I had the same problem with a set of 29's. Ended up being the valve and needle seat. If somebody put a stock mikuni needl seat and its threaded holder, you are leaking by at the threads. Smooth bores have their own thread type even though they are similar to the stock units but willo not work because of the different thread.

I apologise, I just chimed in on a reply to you thinking you had 29 smoothies. I do have a set of the 28 vm sc carbs in excellent shape if you cant get yours sorted out. There even polished. Give me a jingle if you get tired of messing with yours. Mine work very well. (Mike 701 425 7461) in Hurricane, Utah now.

I bought a brand new Z1A new in 1974 for $1895 {yes Im old} when I lived in Miami Fl. at sea level. The bike ran perfect stock & with a 4-1 RC Engineering pipe on it on totally stock jetting. The bike ran 12.19 @ 108.95 with that setup. There is no reason that the bike would need to be richer at your altitude. Im at 3700 ft here in Montana and I just sold a 73 Z1 last year with a 4-1 and stock jetting on it. You have a vacuum leak or another problem some where , it isnt in the jetting