CB77 Carb Issues

SeanCB77 · Post by **SeanCB77** » Wed Jan 22, 2014 1:21 pm

Hi, I recently bought a '68 Superhawk, CB77-1055165
It sat in storage for 20 years, ran great when parked, and the motor turned free.
I changed the oil, cleaned the points, new battery, and rebuilt the carburetors with a kit from Retro Motorcycles on ebay. I left the main 140 jets on the carbs because the kit came with 100, 105, 110, and 160 main jets, all the wrong size.
The bike fired right up. But, it would only run if the choke was on. Once I took the choke off, it would rev up once and then die. It did this several times, even after it warmed up for a few minutes. Also, any time I twisted the throttle, it died immediately.
I read a lot on this forum and last night, I went through the carbs again.
- adjusted the float height with the eyeball method almost even with the bottom of the main jet holder (they were way off) by bending the tang slightly.
- Ensured that the slides were not installed backwards and reverse.
- Tightened the carb flange nuts just past hand tight
- Checked and re-cleaned the jets
- Checked the petcock bowl and filter (both clean)
- Float needle is in the middle position
It started up again with the choke on. I let it warm up for 5 minutes, and when I took the choke off, it idled! Success! But when I twisted the throttle, it died immediately. Repeat, same thing. Does anybody have an idea of what would cause this?

Any advice is much appreciated!

Sean

sarals · Post by **sarals** » Wed Jan 22, 2014 2:09 pm

Sean, I'm hardly an expert, but one is likely chime in. However, I didn't want to see you hanging while you wait! I can offer this. From my limited experience, I'm curious where your air screws are set. LM recommends for a first run that the screws should be adjusted to 1 1/8 turns from fully seated.

Hoosier Tom · Post by **Hoosier Tom** » Wed Jan 22, 2014 2:12 pm

Did you verify that the slides are lifting at exactly the same time? You don't say if you checked the timing and adjusted the valves in your write up. Did you change the plugs or at least check the old ones? Definitely some things you should do before firing up a bike acquired from a P.O. after a long slumber.

HT

SeanCB77 · Post by **SeanCB77** » Wed Jan 22, 2014 2:34 pm

The slides are lifting at the same time.
New plugs
Air screw is 1 1/4 turns out from seated. I will turn them slightly, but I don't think that is causing the bike to die with any throttle.
I have not done anything to the timing or the valves

Hoosier Tom · Post by **Hoosier Tom** » Wed Jan 22, 2014 2:44 pm

SeanCB77 wrote: I have not done anything to the timing or the valves

I think now would be as good a time as any.

HT

Hoosier Tom · Post by **Hoosier Tom** » Wed Jan 22, 2014 3:49 pm

It wouldn't hurt to check compression either. If your valve adjustment is too tight your valves won't seal properly, especially after it gets warmed up.

HT