1977 cb750 carbs

[sfaulk320]

I checked for vac leak using that method no change in rpms the screws are set back to 1.5 the filters are back in the bike when testing. I didnt really play with the needles i just pulled them out as a whole assembly when i cleaned it so idk anything about slots?

[Re-run]

Are you still running the airbox? If so, what brand air filter?
One thing to keep in mind is these carbs don't take super kindly to stabbing the throttle if they are not fully tuned.

If you have everything working as far as accel pump and such, then they need to be synchronized using vacuum gauges. If this is not done, throttle response will be lousy no matter what. And any time you remove the slides, that usually has to be done.

After a good sync, then the fuel screws need to be adjusted for best performance. But you at least need the sync.

[TOOLS1]

When you cleaned the carbs, did you remove the pilot jets to clean them? Also the fuel screws do not do much at high RPM. They tune the fuel circuit at idle up to mid range.
TOOLS

[Re-run]

Off idle is where it sounds like his issue is, at least right now. Pilots catch a lot of people since they don't think they are removable.

It is pretty easy though. Wrap something thick around the jet, as long as it doesn't easily tear, it is fine. Grab with pliers and twist gently and pull. Works almost every time. I have had to gently rock side to side, but it was miniscule movements so I didn't crack the housing.

I also prefer a copper wire or jet cleaner for cleaning. I find soaking and compressed air aren't enough.

Tools, one of these days, we really need a good write-up of the 77/78 carbs with pics.

[sfaulk320]

Like i said guys, the bike idles good i can start it up walk away for a half hour and it will still be doing is own thing. I can slowly twist the throttle untill i have no more to twist its if i really give it a twist it will cut out, i believe every thing is clean and clear. Your words of wisdom are very much appreciated thank you may be this may help. http://youtu.be/_kulB0mhiOM

[shinyribs]

I'm retarded. My bad. I have no idea why I thought you had a DOHC.

Bike sounds super rich. Likes it's struggling to clear it's throat when you are steadily opening the throttle. As far as the sudden "whack" , sorry, I can't help. I've never dealt with keyhole carbs.


Do the keyholes have o-rings for the idle mixture screws? I know the DOHC CV's do and the roundtops don't. Just throwing out any ideas I can. Good luck buddy.

BTW, your bike looks awesome!

[TOOLS1]

It has PODS! You need to richen it up. Drill the pilots out to .45mm, and raise the needle jet a clip. That should get you close.
TOOLS

[Re-run]

I seem to remember asking if he still had the airbox. That would have been good info to have.

[sfaulk320]

You did ask the question and my next post was with the video so you guys could see the set up of pods and 4 to 1 exhaust so i didnt have to type it the video was easier to post a link.

[shinyribs]

It's all good, we're all on the same page now. Keyholes with pods.

I've never owned keyholes, only roundtops on a SOHC. But with your setup you'll need more fuel than stock. How much? I wish I knew.

Where are you now on jet sizes?

[sfaulk320]

To answer the jet size question i do not remember the number 113 keeps popping in to my head i should have wrote it down with the rest of my notes idk what they had stock. I located the stock air box off the buddy i bought the bike from he had it for only a month or two and didnt want a project this size thats how i ended up with it. I did tape the pods up to try and cut back on air and it worked well atleast enough i could ride it around the block a few times. To change the setting for the needle. Will i have to remove the carbs fully and pull the slides and all out or is it done with the screw you can see when the tops are off.

[TOOLS1]

You must remove the slides from the carbs to change the needle position. However the slides can be removed without separating the carbs from the rack. Lucky1 did a write up about here some time ago, and a search should find it. The good part is that since you have 77 carbs, you should have adjustable needles, and not need shims.
TOOLS

[Re-run]

As TOOLS said, the pistons come out. After doing this, a sync will need to be done again. Most work can be done without worry, but removing the pistons will require a sync otherwise the bike will sound like a washing machine when idling.

[sfaulk320]

I got the stock air box on and its about the same so my next step it to play with the needles i havent found the write up on it yet im gonna keep looking. Any one know if there are some people on here local to pittsburgh?

[sfaulk320]

I figured out how to get the slides apart while on the rack very simple now that i have done it. The clip is at the higest most notch, any ideas on where it should be?

[TOOLS1]

Clip and needle positions are confusing at best. Raising the clip lowers the needle and leans the circuit out. Lowering the clip on the needle raises the needle and richens the circuit. Shiny felt that the bike was running rich, so you would want to lower the clip on the needle. I would go one notch and give it a try.
TOOLS

[Re-run]

I think you meant, raise the clip to drop the needle.

[sfaulk320]

I got what he was sayin i dropped the clip one it runs alil better still has that dead spot im gonna play with the accelerator pump it still seems like its not squirting soon enough, plus i have to buy the sync tool.

[Re-run]

Now, since you removed the slides, did you resync again? If there is anything that causes a resync to be needed, it is that. Also, have you tuned the idle mix? If not, that could contribute to the flat spot.