Motorcycle Repair: CT90 CARB Problems, air fuel mixture, lean mixture

Question
I've got a ct90 from the 70's, I'm not sure of the exact date, that
started giving me some problems whenever I would be in the high
end of any gear. It would start sputtering and missing fires. So, I took
the carb apart in order to clean it and check for missing parts and
saw that an O-ring around the needle set jet(the jet that houses the
throttle needle) was melted or rotted out. I've replaced the o-ring and
now it gives me new problems. I've managed to get it started a few
times, with many many kicks, and whenever I get high into any gear
and let the engine slow back down, it starts to sputter out and die,
even if I shift it into a lower gear to try to get the revs back up. After
it dies like this, I have to wait a while in order to start it again. When
it finally starts again, after many many kicks, it starts very slowly and
it stutters while starting. It will slowly die again in the same manner
within less than a mile. It seems to idle without and problems, it may
sound a little off, but not bad enough to miss fire. I also get a lot of
back firing whenever I take it down a hill with the throttle closed.

One more question: When I put the carb back together I didn't
remember which way the needle that supports the float goes. I've it
installed with the little spring loaded tip touching the float. Is this
correct?

Thank you for your time and any opinions you may have for me,
Jake

Answer
The backfiring indicates a lean air fuel mixture.  It could be you didn't get the float level set correctly.  If it starts pretty good cold and runs poorly hot it's a rich mixture but if it starts poorly hot or cold it's more likely a lean mixture.  When it's running bad put a little choke on and see if it improves.  If it does, this is a sure sign of a lean mixture.

It sounds like you go the needle in right.

Regards
Rich