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Symptoms of Lean or Rich carb settings on a motorcycle

I have a '71 Honda CB350 that is new to me. I recently rebuilt the carbs and replaced the petcock and had it running pretty good for awhile. I saw your in depth answer here for a question about running lean or rich.

I replaced the plugs only two weeks ago. I pulled my new plugs and I saw that the right one was black - indicating that it runs rich (right?). The left plug looked ok (I think). I also saw that you mentioned that if it runs with choke open then that means it runs lean (right?). My problem that brought me to that thread was that I am not getting enough power when I am in the low gears. If I try to get into first nice and easy then the engine putters but gets going eventually. It works a lot better if I use a lot of gas to get through those first 2 gears. The bike was running ok, granted only with the choke open for about 100 miles but now has developed this problem.

What do you suggest?

Also, I live in Denver so is altitude an issue?

When I rebuilt the carbs I used the 105 main jet that I learned was stock. Should I change that to the 115 that was also sent with the kit for any reason?

Thank you so much for your time. I really appreciate it as I learn how to trouble shoot this bike hopefully I gain some wisdom through this process that I can one day pass on to someone else. Thank you.

  • Those carbs have a vacuum diaphragm that often go bad and are not included in carb kits, more than likely one or more of the diaphragms has a hole in it,... common-motor.com/honda-cb350-carb-diaphragm – Moab Aug 27 '16 at 1:16
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    Do you have a Honda carb synchronizer and done a balance. – spicetraders Aug 27 '16 at 2:13
  • Do you have an aftermarket exhaust or modified air intake? – DucatiKiller Aug 27 '16 at 5:29
  • @DucatiKiller yes it looks like the exhaust is after market. – JohnGardnerIV Aug 27 '16 at 21:53
  • @DucatiKiller I just cleaned the air filters pretty well and also ordered new ones but it seems like that helped the sputtering a bit for now. Hopefully the new filters will do the job. Still have the choke open problem. Only runs when choke is open. – JohnGardnerIV Aug 27 '16 at 21:56

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