Help with carbs on 1967 CB77

[mach1970]

Okay here is the deal. Been trying to get this bike back on the road for a year now of and on. The carbs have been giving me fits. I have never so much trouble getting a bike to run correctly in all the 100 bikes I have restored over the years. Anyway, problem is, it will start right up and idle beautifully. Try to pull out from a stop and it has no power, just bogs and doesn't want to go. Once it coax it from the stop and get the RPM's up a little bit it runs great. The carbs have been cleaned numerous times and rebuilt with all new jets. Problem there is that the pilot jets keep coming in different sizes, even sets of jets with the right numbers will have different size holes in them. So I'm not sure if I have the right pilot jets or not. I know the timing is spot on, checked it statically and fine tuned with a timing light and it is good.

Other thing is that in order to get running as good as it is, the mixture screws have to be set to 3/4 turn out. That doesn't seem like enough to me. Anything else it won't pull out at all. In fact I can turn them all the way in and the bike still idles.

So, is it the pilot jets not being correct, or could it be the float height. It is set to stock height but I have had other bikes that wouldn't run at the factory settings either. Also I have seen confusion on what they should be set at.

Thanks for the help.

Rob

BTW: The points are brand new and so is the battery. And like I said the timing is spot on.

[davomoto]

Did you set the points and timing with Eds tuning recipie? If not, do yourself a favor, and follow it to the T . The pilot jets should be 42s. Are you running the jet needles from the keyster kit? I prefer to re-use all of the Honda Kehien brass whenever possible, especially the needles. Stock float height is correct forr these bikes.

davomoto

[mach1970]

Thanks for the reply, but yes the timing is spot on. I did Ed's tuning recipe one better and checked the timing with a timing light and it is correct. Also I have two sets of pilot jets that say 42 on them, and the holes are totally different sizes. I was using the needles from the rebuild kit and then switched back to the original needles. Problem is I don't know what state the carbs were in when I received the bike. Like I said it is fine at idle and fine once the revs get up a little bit. It just won't pull out from a dead stop without alot of coaxing.

Also the fact that I can screw the mixture screws all the way in and the bike still runs, tells me that the carbs are still getting fuel somehow. Possible stock float height doesn't always work. If no one has any other ideas, I guess I will try decreasing the float height and see what happens.

Thanks again,

Rob

[davomoto]

Rob, did you blow comressed air through all of the passages in the carbs. Two of the three holes in the rear bell should be able to have air blown through them.

davomoto

[Spargett]

I had a number of issues just like yours, which turned out to be related to my float height. A combination of them not being measured EXACTLY right and the tang being bent in an odd shape, and therefor not depressing the valve needle correctly.

Make sure to measure 22.5mm EXACTLY from the dip to the top of the float as it's just touching the needle, but not depressing it. There's a small dip along the side of the body. Make sure to RE-TIME after adjusting the float height.

P.S. Also check to make sure the floats aren't getting stuck on the rim of the gasket. You can bend them inwards just a bit with your fingers.

[Goodysnap]

Yep critical alright. I attatched a piece of fuel hose to the inlet so I could blow air in the inlet(w/ my mouth) so I could tell exactly when the needle and seat would stop flowing fuel.No question they are right on w/ this method.

[teazer]

The symptoms certainly sound like insufficient fuel at and just off idle.

The fact that the jets have different sized orifices, suggests that they may be the wrong jets. SOund odd I know but it might be worthwhile trying say a pair of 45s.

You might also check the slide to make sure it isn't too loose in the bore and inspect the needle and needle jet. If the needle and or jet were worn that should make the mixture too rich, so that isn't the cause.

It could be that you have a slight air leak and I'd start with the tufnol spacer and the carb flanges. They bow when overtightened. clean up the carb flange face and both sides of that phenolic spacer and replace teh O rings and see how that works.