Topic: 77' Cb750 Carb sync

[maceo]

I was wondering if anyone can help me troubleshoot my carbs.  When I start of in First Gear my bike wants to die, unless I leave the choke out.  It works fine any other gear and at Idle.  IS my problem the accelerator pump?  Or something else

[tango911]

many will say do some searches on the site. Theres tons of info on this site about carbs and tuning.  Sounds like you need to spruce up on how carbs work and maybe get yours cleaned and tuned. You also need to do a regular tune up as well.  Points, timing, spark plugs etc....
If you cant find what you need im sure some one will chime in with more info or questions about what type of carbs you have and what the screw settings are, what size jets you have,  are you running stock air box and what kind of exhaust do you have? 

good luck

[maceo]

Carbs were just rebuilt and sync'd (not by me).  The points have recently been replaced and an engine tune up was done.

[TwoTired]

Everything on the bike stock?   Induction and exhaust?

Tune up include a new air filter?

Anyway, you are staring with the assumption the carbs are the problem, probably because they are a mystery to you.  What has made you eliminate everything else on the bike as part of the problem? 

For all we know, you have removed the air filter and that is contributing greatly to the issue.

How many guesses do we get about what you have?

[maceo]

yes everything is stock, and it has pod air filters that are new. I have not eliminated anything, I just think the carbs are the most likely cause due to the fact its only during starting in first gear.  if I am wrong please let me know. 
I would not say the carbs are a mystery as much as I am asking this website for help hoping someone else has had the same problem.  If i do not need to open the carbs I would rather not.
and you may take all the guess's your heart desires brother

[Cuts Crooked]

yes everything is stock, and it has pod air filters that are new.

Sounds like there's yer problem. When you go to Pods you need to rejet.

[Spanner 1]

Your bike is not 'stock' as you claim if you have installed pod filters as now the carb parameters are different, brother  .... pull off the pods and twist the throttle while looking into the carb throats. A good squirt of gas must be visible in each carb if the accelerator pump is functioning.

[Stev-o]

Pods will mess with you every time

[maceo]

Ill check the fuel being squirted in from the accelerator, thanks. 

[chickenman_26]

If i do not need to open the carbs I would rather not.
and you may take all the guess's your heart desires brother

These are emission control carbs that run pretty lean, and anything that makes them run leaner (like pods or vacuum leaks) is going to cause flat spots and running issues. First thing I'd do is warm up the bike, let it idle, then spray carb cleaner at all of the carb-to-head rubber connectors. Those rubber connectors develop cracks and splits that are not easy to see but will create vacuum leaks and crap up the performance. It's also possible that the carb throats aren't fully seated in the connectors - they're very difficult to get fully seated. Either way, the idle will change noticeably when the carb cleaner gets sucked into the leaking area.
There was a guy on this forum a while back with a problem similar to yours, and he kept swearing the carbs were fully seated in the connectors. Then he showed us a picture, and guess what? Just saying....

Carbs were just rebuilt and sync'd (not by me).

Either good or bad news, depending on how familiar the rebuilder is with these type carbs. Was this off-idle flat spot there before the rebuild? If yes, the slow jets/idle passages may be partially plugged. Those jets are pressed in, and most folks think they can't be removed. They can be, and it's necessary to insure they're clean. Did the rebuilder install the carbs and synch them on the running bike? If he only bench synched them, he may have done a good job, but maybe not. The synch needs to be adjusted after installation with the bike running.

Ill check the fuel being squirted in from the accelerator, thanks.

If you see a healthy squirt in all four carb throats, that's good. If not, the pump diaphragm could be defective, or either of the 2 pump check valves could be plugged. Also, there are brass orifices in the rubber hoses connecting the accelerator circuits of #1, 3, and 4 to the pump outlet on #2. If any are plugged, you'll see a good squirt into #2, but maybe not any in one or more of the other carbs. Bottom line, these carbs are great when they're right. But they're more complicated than the previous types and have more places where crud can go undetected if the cleaning isn't extremely thorough.
Good luck.

Stu