Cant Keep 77 CB750 ideling

[TOOLS1]

I often have the same problem with the clamps. If the boots are nice, and soft it does not take much to seal them. However on the old ones.... When I buy new clamps at vintagecb750.com I get the smallest size they have. The ones they recommend are just too big. Or I buy 8mm wide hose clamp kits on e-bay, and make them up myself.
One of the things carbs will do when out of sync is make the engine run at high RPM. I know some people have had good luck with bench syncing, but I sure haven't. Especially with these keyhole carbs. It's best to not mess with the sync screws until the gauges are attached.
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P.S. If you really want an easy fix for your bike. Just send it to me with that matic engine, and it will magically run perfectly.

[motogrady]

Sorry bout that guys, thought the over reving from an air leak was exclusive to CV's.

You got any slack in throttle cable?
If we're not dependent on vacum lifting the slides,
and they all are closing fully when throttle is off,
where is the air coming from?

The clamps, I tighten till the rubber starts to squish, and then some.

[zedx]

The slides come all the way down when let off on the throttle and the choke snaps back when let off. When I bench synced them I put a small drill bit, maybe 1/16 if an inch in the rear of the slide for all. So I don't think that is the issue.

When I pulled the idlers out I noticed they were #35's, that seems really small could I just not have enough fuel going in there especially because there is no pods or box on the carbs? Have the pilot screw out 2 turns as of right now.

I am going to the hardware store after work and getting new clamps.

[TOOLS1]

These carbs sync to the #2 carb. And since the #2 carb is not adjustable, you can not just pick up a drill bit and sync them. Also there are many little things that affect the carb sync between cylinders like slight differences in compression between cylinders, and wear in the carbs themselves. The ONLY way to properly sync them is to have gauges, and do it with the engine running. Also the not having an airbox, or pods on it will not affect the carbs at idle, or the syncing.
Honda did design these carbs to be lean. This was the era when the EPA was cracking down on emissions you know. That is one of the reasons these carbs have an accelerator pump. However you can drill the pilot out with a .45 mm drill bit. This will make a big difference in starting, and low RPM performance. It will also keep the engine from knocking/pinging.
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[zedx]

Thanks guys! I Will take all the advice you have given me and see what I come up with over the weekend. Hopefully it will be good news and not a ton of questions due to my inexperience.

Really appreciate it!

[zedx]

So I didn't get to work on the bike as much as I wanted to but I did find time to lash the valves. All were off except one, started it up and it seems to idle fine/better but what I did notice is that when I lift the bottle of gas up in the air to refill the bowls it wants to start to speed up the idle. Not sure if this will act the same when I have the tank on or not, guess I'll just have to find out once its on there.

One Question I have, Tools you may no this since you have so many Hondamatics, is what is the main difference between the Hondamatic front caliper and the regular CB750 calipers in 77? they look different, does one work better than the other? are they interchangeable? the reason I ask is the one that is on my bike the bleeder valve was broken off of it and the line nut is seized in there so I think it needs replacing.

[zedx]

Hey guys, Just wanted to ay THANK YOU! Worked on my bike for a while yesterday and now it is idling and revving strong without hanging up.

Thanks to this forum and the help of all of you that provided advice made it possible to repair myself without having to take it to some shop that probably wouldn't know how to fix it in the first place.