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I have been playing with the carbs on my 78 Cb400A, which should be the same and this is where I am as of right now. With the stock air box and the same Emgo mufflers as you have I am currently running a 112 main jet and a 92 secondary jet. I have the Idle screws turned out the factory 1 1/2 turns and it seems to run pretty good. I am getting 85's for the secondarys tomorrow and will install them and report back as I think its a little fat in the mid range. I tried a 125 in the mains but with the mid being fat it was just too much and would bog real bad at high rpm. I figured its easy to go overkill and work down from there rather than try and sneak up on it. Good luck and nice progress.
I'll be cracking the carbs apart again over the weekend and double checking everything. I probably won't be able to fire anything up until Tuesday. I'll report back then. Maybe with a video.
Made a little video of what's going on. Mains are 120 and pilots are 78. Mixtures at 2 turns out. Start with full choke and only left idles. Ease off the choke and then only the right idles.
Use the "stumble" method with your air screws for now. In until it stumbles, out until it stumbles, find the number of turns that is in the middle of each stumble. Get it idling the best you can (even if one side), turn the air screws in or out. I'd think you'd want to turn them the direction that makes them more rich at this point. I bet you aren't getting enough fuel to the one side that isn't firing at idle.
Well I was working on the carbs and trying to get the oil/neutral light to work on my gauges at the same time. I was using a little leader/jumper wire to test connections. Went to grab a tool in the garage, the wire had come off and grounded to the frame.
Hooray for fuses! Check out the little jet of (guessing) melted glass with the little white orb coming from the middle fuse. But, that ended my testing of the carbs.
So, I moved on to the front brake. Do these look like they can be saved?
Not sure on the brake pots, I'll let someone else anser that, as for the fuse box. Take 20 mins and remove the fuses, then clean all the holders with some rolled up emry cloth. I had good fuses but the little bit of corrosion on the clips was enough to make current not pass etc. It will save you a lot of headaches when looking for electrical gremlins.
The short answer on the brakes is yes...you MAY wan't to get a new piston, but that one doesn't look too bad. (the rest will clean up fine) I found that a dremel with the wire wheel attachment works great to get into the spots holding the gaskets. THROW THE OLD RUBBER GASKETS AWAY and get yourself a brake rebuild set with new ones for your safety.
I've been looking for rebuild kits but can't find any specifically for my model. I'm letting them sit in diluted CLR. I'll be installing a mini fuse block as soon as it gets here.
I borrowed some ideas from a couple of fellows around here.
The pipes are a little too close to the rear-sets than I had anticipated. They're also about an inch from the carb bowl; how concerned should I be about that?
Check your carbs to be sure the slides are moving free. If one is stuck either up or down it might cause your idling issue. Those old Keihins can cause lots of grief that way. The ones on my Yamaha were actually missing the spring on one side. Even a little wear can be an issue. Pull those top caps off and move the slides through them. If there's any sticky spots, try polishing both the insides of the caps and the outside edges of the slides. LIGHTLY. A loose fit is just as bad.
If you have a concern about the exhaust being too close to the carbs, you can always Fab up a heat shield.
To give an opinion on the pipes being close to the carbs....(note I didn't say answer...ha!)
You may want a heat shield between the pipes and carb if that's possible. While moving, I don't think you'll have any real issues (the carbs are so close to the heads anyways) but when stopped you "might" just help the fuel evaporate a little quicker from the bowl I dont' think you'll get any ill effects from it though. The lines aren't close enough to cause vapor lock or anything.
I don't understand why people love to hate these machines...IMO they have a lot of potential and the engines are just about as bulletproof as they come. Your project seems to be taking shape nicely. You're going to want some earplugs
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I dont' think you'll get any ill effects from it though. The lines aren't close enough to cause vapor lock or anything.
