Hopefully I'm not going to get a bad reputation for reposts, but I didn't see any thing easily found in the search I did...
Got my CB77 running pretty decent everywhere but 80-100% throttle. My friend mentioned that it sounds like a main jet issue but couldn't tell me which way it needs to go. Is there an easy way to tell if it is rich or lean if there's no smoke and my plugs are too old to read accurately? The sound it makes is almost an overly throaty bogging and the power decreases quite dramatically. I don't like to do it too much in case it is lean. Is there a specific sound to a rich mixture or lean mixture?
I'm not lazy or anything, and if I'm not 100% sure I'll just swap out for a richer jet and play it safe. Its just right now, with the bike actually moving under its own power, I want to minimize down time swapping out and dismantling carbs! I wanna RIDE!!!
Thanks for any help!
Rich or Lean?
Assuming the carbs are clean and floats are set correctly and there is no restriction to fuel flow, and the points and timing are fine and valves are adjusted properly and the air filters and exhaust baffles are all fine and the motor has good compression and no air or exhaust leaks, it's time to start adjusting the jets
Fortunately on a CB77 it takes only seconds to remove a float bowl and swap out a jet. I'd start with new stock sized jets if everything else is stock and OK. Then I'd go up two sizes and see if it's better or worse. You could try applying a small amount of choke to see what difference that makes, but it would also be obstructing air flow so would not be conclusive.
Choke seems to hurt more than help, but haven't played with it enough yet. My neighbor (who happens to own something like 13 Superhawks) said that my ignition "sounds okay". I don't know. I'll be checking that very soon as well-- likely when I'm doing the carbs. Baffles are removed and the filters look pretty good. Haven't checked compression yet-- maybe I'll do that later as well. The previous owner said that he tested it and it was good and I've only had the bike a few days, only been running for one. It runs so well everywhere but full throttle that I (and my neighbor) feel it must be something like a main jet... am I wrong in this assumption?
Try driving it without the airfilter. If it runs a little better, it's to rich if it runs a little worse, it's to lean. Also, make sure your main metering valve needle is in good shape. I feel for you, carbs can be tricky. Make absolutely sure your float level is set right and your jets match the elevation you live at. Denver needs different jets than Miami etc.
Good pointers there.
BTW did I understand you to say that the baffles are removed and not fitted? In my experience (limited) they run like crap without baffles in the pipes. All noise and no go. I would work through all the usual things to get it in tip top shape. I think there are posts here on all that basic set up stuff. Start there and you will know what the points are like and how the timing is set and when you strip the carbs you can see what's inside and KNOW where you are starting from. Re: Rich or Lean?I don't know the benefit of not installing new plugs as the first order of business, but I'm not an expert on the topic.
Okay, so as I mentioned in the Ignition thread, I took that apart, put it back together, timed it both by Ed's Recipe and by the timing light, installed new plugs, cleaned out the entire fuel system with the exception of the carb jets, and ran it again. It still sucks. If anything, its a bit worse. I took a 10 mile ride today which ended in the bike running so poorly that I had to limp it home.
When I had the air filters and hoses off I ran the bike as was mentioned in "The Recipe". It idles like a CHAMP now and runs fine under about 25-30% throttle. As soon as you start putting some twist into it, the thing sounds super throaty and even sometimes makes a loud crack out of the inlet of the carb. It also SPRAYS fuel out the inlet as well. Does this mean it is grossly rich now that something freed itself in the fuel system? The timing is for sure right. It's a touch retarded at idle but is dead on the mark above that. Here's a video of it running as I mentioned. Toward the beginning you can hear it backfire through the carb. You can't really hear how extra throaty it gets when it starts to miss-- I guess that doesn't come across on an iPhone mic. You also can't see, but my phone (and face, and hand, and shirt sleeve...) was covered in spraying fuel from the carb inlet. http://www.flickr.com/photos/likesitsid ... 963499839/ Any help would be appreciated!
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