Left side firing issue
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  1. #1
    Member troyfeener's Avatar
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    Left side firing issue

    Hey gang. I'm so close I can taste it....but stuck and need some help to get her ready for riding season here in Alberta.

    Here's the situation:

    '73 CB350 K5...was pretty much stock as far as I could tell and in good shape, running when I bought it last summer and she rode ok...had a few electrical issues, that's it really.

    Over the winter I did the following:
    1. New wiring harness.
    2. New solenoid, coils, condenser, RR, Battery
    3. Rebuilt starter motor
    4. New drag bars and brake master cylinder, disc pads and brake cables
    5. New headlight and LED signals, dashlight, flasher relay.
    6. New clutch plates and shift lever.
    7. All new cables
    8. Rebuilt carbs.

    So I rolled her outside now that the weather is above 0C and tried to start her up and all I got was some serious backfiring...neighbours nearly called the cops. Took a bit but I figured out I had the wiring backwards on the coils so I swapped them and she fired right up.
    Proceeded with cam-chain adjustment, valve adjustment and points/timing adjustment. Fired her up again - right side pipe got hot fast but left side seemed to not be as hot. No backfiring, idled at 1200 choked. Opened the choke up and she reved up to 3000....hmmm. Checked the mixture screws and they were open 1/2 turn each. Then I notice that there is oily gas leaking from the collar on the left exhaust and also spitting out the back. Shut her off and pulled the plugs and both sides are pretty black, but the left one is also really wet with gas.
    Pulled the carb and checked the float-bowl....26mm, no leaks in the float.

    So here is where I'm stuck....where should I look for firing issues? Did I screw something up when I had the coils wired backwards? Any advice would be helpful. Cheers.
    72/73 CB350 Green

  2. #2
    Sensei 66Sprint's Avatar
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    First mistake.... Adjusting valves while warm.... This should be done with engine "stone" cold.....
    And, are the secondary index marks correctly oriented?
    Why are your mixture screws closed to 1/2 turn, and not preset to within the 1 turn plus or minus 1/8 turn factory range specifications?
    Rev /choke problems sound like an intake air leak.....
    Also sounds like your points timing is incorrectly set......
    My phone: 540-525-5199
    Last edited by 66Sprint; 04-13-2019 at 05:36 PM.
    "I have a mind like a steel trap.....Old and rusty, of antiquated design, and hard to get stuff back out of...."
    Contact info: E-mail; [email protected] Phone; 540-525-5199

  3. #3
    Member troyfeener's Avatar
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    Thanks Sprint.
    I'll re-adjust valves when stone cold.
    I had forgotten to set the mixture screws after rebuilding the carbs a month ago...noob. They are now correct.
    Points are also new and set to fire on compression stroke at LF and F using continuity tester. I don't have a strobe.

    I'm all cleaned up now...back at it again tomorrow I hope. Can I call you tomorrow to discuss?
    72/73 CB350 Green

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  5. #4
    Sensei 66Sprint's Avatar
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    Sure....
    "I have a mind like a steel trap.....Old and rusty, of antiquated design, and hard to get stuff back out of...."
    Contact info: E-mail; [email protected] Phone; 540-525-5199

  6. #5
    Senior Member mike in idaho's Avatar
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    Try a fresh spark plug on the left side, in case it got gas-fouled when you first tried to start it.
    '65 YG1
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    My company car is a Kenworth

  7. #6
    Member troyfeener's Avatar
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    Thx for the suggestion Mike. I cleaned up the plugs with brake cleaner and a wire brush. Gap is bang on still. Should I still put a fresh one in?
    72/73 CB350 Green

  8. #7
    Member troyfeener's Avatar
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    Hey Sprint. Spent the day on electrical instead...wiring up a new tail-light. Didn't want to bug you on a sunday with a phone-call.

    I double checked the secondary index marks just in case but they are facing out.

    I've also put new boots/gasket on so not sure if an air leak would be there....I'll check with some WD-40.

    Thanks for the help gang. Fun times...
    72/73 CB350 Green

  9. #8
    Senior Member sikeclass's Avatar
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    Watching this thread. Pulled my 72 cb350 out of winter storage to try and get it going over the weekend, and it was spitting gas out of the left exhaust. Left pipe is stone cold. Put in a new battery and static checked the timing. Seems to run stronger, with stronger pressure out of both exhausts, but left pipe is still cold and when strobe testing new timing, both sides are firing when the mark hits the stator lump; so a few degrees early.

    Quit everything because I was worried about fuel in the oil. Going to spend a day this weekend doing valves, and timing again, along with oil change. Watching this thread for any tips about that much gas making its way through the system.
    - 1972 Honda CB350
    - 7 years and 4 crates of spark plugs later, it runs, but there's definitely room for improvement

    I've made a lot of mistakes, some which I haven't realized yet. Any questions, opinions or info has to come with that huge grain of salt.

  10. #9
    Member troyfeener's Avatar
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    The plugs that were in there were B7ES so I've ordered some B8ES plugs. Will redo valves as well and double check my timing again. Checked the compression on the weekend and it's still good at 170psi cold. Keepin' on keepin' on.
    72/73 CB350 Green

  11. #10
    Member cb360j's Avatar
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    Make sure timing is spot on, and ensure carbs are fully seated in the intake manifolds (boots), saying this because high idle sounds like vacuum leak.

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