1980 cb 750 carb issues

[stevew]

So I have a new to me bike that I'm in the process of getting road ready. A little history on this bike, I worked on the carbs a couple of years ago on this bike for a young man that I worked with. I got it to run but it would not run with the air filter in it but would run pretty well without it. I wanted to tear the carbs completely down and buy new kits and rebuild for him but he didn't want to spend the money to get it running right. Long story short he ended up haveing another guy work on them and he ended up charging him $250 and still didn't get it running correctly. The bike ended up in stroage for the last couple of years while he was at college and the guy that had it then had health issues and could not get to it. Anyway, I had kept track of this bike and I have ended up with it for free. The bike is complete and only has 16,000 miles on it. I have got it to run and it starts right up and revs good and hard but I can't get it to idle right, I adjust the idle screw where it will idle but then you give it some revs and it won't come back down. If , I adjust the idle screw out and use the throttle to keep it running it will rev and return without issues. I have dipped the carbs and cleaned them very well. Everything works on the bike it even had new tires on it with less than 100 miles on them.  Any help on the carbs would be appreciated.

Sorry so long guys.

Thanks,

Steve

[runabout879]

Did you download the repair manual? There is a troubleshooting guide in there under fuel system. I know it has a part about not returning to idle. Check it out. I know that trouble shooting guide helped me figure out what was wrong with the carbs on my 81K.

[stevew]

I tried to download the manual but I couldn't get it work on my computer.

[Dw07u]

Try the backup link...

The Normal ones seem to be faulty... Below will be in PDF format

http://www.mediafire.com/?ntncy2gy8wa8tub

[LukeM]

Hmm.  Stock airbox or pod filters? The stock carbs for these bikes are a constant vacuum design, and really run better with the stock airbox.  They can be rejetted for pod filters, but it's a LOT of work. Search on "pod filter" on this forum to see other postings.
Another thing to check is exhaust.  Sometimes if the carbs are stock and the exhaust is unbaffled (straight pipes, for example), the lack of back pressure will make the return to idle a bit longer.

Go through the manual first and try the simple things.  Good luck, and I hope this helps.

Luke M

[TOOLS1]

This one has me stumped. I have never had any experience with the DOHC models. I guess I would check to see if the adjusting screw is bent, or if the throttle shaft is hanging up at the point where it hits the screw when it is adjusted out.
TOOLS

[Re-run]

Did the manual download?  What happened when you tried to open it?

Edit: I downloaded the file and tried to open it directly and it was blank. Then I opened my pdf reader and selected the file and it opened fine.
Try that, bit odd though.

[stevew]

I got the manual to download on my computer at work. I'll be going through it and working out some of the bugs on the bike. I went ahead and put the stock airbox back on (what a pain in the butt) bike didn't run much better so I'll keep at it. I might put the pods back on and rejet it to perform better. It did start easier with the pods and reved easier.

Any other suggestions would help guys.

Steve

[Peterwh]

Have you balanced the carbs using vacuum gauges?  Mine ran rough at low revs and balancing the carbs fixed it, they were way out.