My "new" CB750

[MarkPBG]

So i got it Saturday, changed theplugs, fixed the leaky fuel lines, and drove it around the block for about a half hour on several trips.   It doesn't like to idle, and dies 2 out of 3 times when stopped. I think I know why now…at the end of the last trip when I stopped, fuel rushed out of the nipple on the bottom of the inner carb on the right side. (overflow?) I'm more of a maintenance kind of mechanic, so it looks like I'll be bringing it up to a good local shop so he can get it right for me. Today was the last day of my vacation, so tomorrow it's back to the 60 hour per week grind.

[MarkPBG]

Speedo stopped working on the last trip too, almost forgot. I knew it was going to die because it had that big dent in it. It has been mistreated. lol

[shinyribs]

My speedo quit once and on closer inspection i had lost the screw that retains it to the speedo drive on the front hub.The cable seemed to be in place,but was out just far enough to not engage.As far as your flooding it could be a few simple fixes:

Dirt in the needle=clean it yourself and your good to go
Cracked/damaged float=replace it yourself and your good to go
Float simply out of adjustment=adjust it yourself and your good to go

I'd hate to see you rack up a large shop bill,you can do it!

[MarkPBG]

I can definitely do it. I've rebuilt so many Holley 650's, 750's, 850's, and a few Edelbrock Q-Jets. It's just a matter of not having a "shop" area set up in my new house yet. I want to get this one running QUICK so I can ride it…finish up the house interior renovations, set up the home shop, and find a project bike to cafe from the frame up. If I take apart a carb, I'm one of those guys who will do a total rebuild "while I'm in there" lol If I do that, from what I read on the Keihins, they have pressed in jets and the only way to really get that carb clean is in an ultrasonic bath. There's a shop near me that will do it once I get em off and disassembled. Putting it back together is a piece of cake with all the reference material on this and other sites. Now tuning it, that's an art I have not mastered. I can get it up and running, but making it REALLY go….nope, not there yet. LOL

[shinyribs]

If you can tune a Edelbrock/carter these will be a piece of cake.They are dead simple to tune

[MarkPBG]

I've never tuned multiple carbs. I'm always afraid of leaning out one cylinder and burning up a piston. lol

[shinyribs]

Nah,just make sure you have the jet sizes the manual calls for and you'll be good.If your airbox/exhaust is stock,that is.Mine calls for 105 mains and 40 pilots.With pods and very free flowing exhaust i ended up with 125 / 42 and it runs great.I  love how it slides the tire going into 2nd gear!Get a $65 carb sync kit and roll on!It takes longer to get the tools setup than it does to sync them.Its really not bad.I did my first one in ten minutes.You can change jets without pulling the carbs,so its not bad at all.You dont need much shop space,but i like to use a milk crate to sit onIts not at all like tuning multiple carbs on an auto since its one per cylinder

[TOOLS1]

The pilot jets are the only ones pressed in, and they are not hard to remove/replace. I use a 4-40 tap, and just tap the end about 3/16 of an inch (sometimes the jet will come out while tapping it). then I slip a piece of steel break line about a 1 1/2 inch long over the jet. Then put a nut, and a washer on a 4-40 X 1 1/2 inch screw. I then thread it into the end of the jet, and tighten down the nut to pull the jet out. To put the jet back. I just tap it in with the handle of a screwdriver. Also if, you have keyhole carbs. Drill them out to .045. this will make cold starting a lot easier.
TOOLS

[shinyribs]

Mine are threaded.Are we talking about the roundtops here?

[TOOLS1]

The keyhole, and CV's are pressed in.
TOOLS

[MarkPBG]

The other day when I took my test drive, I cold started it. I turned on the choke, let it run until the idle started dropping, gradually closed the choke, and I was good to go for about 6 trips around the block until that carb overflowed. :) Cold start= no problem. :)

[shinyribs]

Its probably the flooding causing a fuel rich condition that lets it do that.Lol! Dont fix it!!!

[MarkPBG]

Ok then…I'll hook up four hoses to the overflow nipplesrunning down to a small overflow catch tank, install a battery powered fuel pump, and run the overflow back into the tank!

[MarkPBG]

According to the manual, the factory set these bikes up VERY lean. Even the manuals I've read recommend going up one size for better response with an all stock set up.

[shinyribs]

MarkPBG wrote

Ok then…I'll hook up four hoses to the overflow nipplesrunning down to a small overflow catch tank, install a battery powered fuel pump, and run the overflow back into the tank!

You are thinking man!Wonderful idea

[LukeM]

Uhmmm...that doesn't really fix the problem, does it?

Overflow suggests a problem with the float or needle valve in the carburetor. There may be a nick or a cut in the needle valve's rubber/plastic portion, or perhaps the seat for the valve is dirty or corroded.  There are ways to fix the seat: some use a bit of polishing compound on a Q-Tip, others are just gummy and work with a little carb cleaner.  If the needle valve is cut, then it's time for a new one.

In the "while I'm here" mindset, what's happened to one carb is probably happening to all of them.  It might be prudent to pull the whole carb bank and work on all 4.  It's not that time-consuming: last time I did this it took about 2 hours to strip them all the way down, clean and adjust, and reassemble.  Just take your time, and document your progress with pictures or procedures.  There's a VERY good write-up that posted recently. Excellent details, and pictures also.

Hope this helps.
Luke M

[shinyribs]

We were just goofing off Luke.Please dont think that i would consider that a viable solution.LOL

[MarkPBG]

That was definitely a joke. I worked at an auto parts store near Loxahatchee FL, and I've actually SEEN some of these "redneck engineering" ideas put into practice! lol Oh the stories I could tell of them good ole boys and their swamp buggies, airboats, 4 Byes, and OMG, the LAWNMOWERS. LOL

[MarkPBG]

Gotcha Luke…it was a joke…LOL Yeah, I've rebuilt a ton of carbs, so it's not really a big deal except for finding the spare time between working 60 hours/week, school 20 hours/week, homework, home renovations, running a side business, and socializing and face booking, and now motorcycle internet boards. LOL. I think I have 15 minutes for it penciled in next month. LOL