CL360 - Idle Adjustment - Can’t raise enough
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Thread: CL360 - Idle Adjustment - Can’t raise enough

  1. #1
    Senior Member jakec's Avatar
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    CL360 - Idle Adjustment - Can’t raise enough

    I just finished rebuilding carbs on a CL360 and it’s running great! I’m really stoked. I just have one problem, the screw-in cable type idle adjuster seems to be maxed out, and the bike is idling about 900rpms. I tried adjusting the idle up with air screws however they weren’t really having an effect (I think) because the idle was so low the bike just wanted to sputter out.

    When I bench synced carbs I did it with butterflies closed, syncing them at the moment of opening. I’m fact I didn’t really do anything because they were already as good as I was gona be able to get them on the bench.

    I was previously trying to fix a hanging idle which is resolved now. I rode the bike around the block and it’s great. However I can’t adjust idle up.
    1975 CB400 F0 Stock
    1974 CB550 K0 Chopper
    1970 CL350 K2 Stock

  2. #2
    Sensei 66Sprint's Avatar
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    Hopefully, you cleaned and re-used all the stock brass, and have the jets in the correct positions.....
    IF SO, and the mixture screws have no effect, the idle passage is still dirty or blocked.......
    Cranking the throttle-stop cable/adjustment in all the way has opened the butterflys enough that some fuel is being drawn through the primary jetting, but only enough to maintain the 900 RPM......

    You NEED to re-clean at least the idle circuit passages and jetting......

    "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
    Senior Member jakec's Avatar
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    I did re use all the stock brass. I found problems during the rebuild and corrected them (dirty emulsion tubes and bad diaphragms). The thing is, the idle adjustment and mixture screws were working fine before, I just had the problem with some times hanging idle or idle racing up on its own (which does not happen now).

    So it seems the idle circuit was not obstructed before, and I cleaned the carbs in my ultrasonic cleaner so I don’t think they would have gotten worse, right?

    What I did during the rebuild was set float height 20mm, resolve diaphragms and bowl gaskets, and general cleaning. I did take the left carb off the rack so I could access the felt washers on the throttle shafts and oil them.
    1975 CB400 F0 Stock
    1974 CB550 K0 Chopper
    1970 CL350 K2 Stock

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  5. #4
    Senior Member jakec's Avatar
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    I just removed both mixture screws to inspect because one was harder to turn than the other. That one happens to be missing the little rubber o ring. Which is odd because I definitely know it was on there when installed. And it’s nowhere to be found. I checked the bore of it’s hole and it’s not in there.
    1975 CB400 F0 Stock
    1974 CB550 K0 Chopper
    1970 CL350 K2 Stock

  6. #5
    Senior Member jakec's Avatar
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    Got two replacement O rings for the mixture screws. Going in much easier now. It did not change anything, though. When I start the bike from cold, it idles "normal" around 1200 for maybe 1 minute then falls to about 900, stays there, then dies. You're right, it's like I either don't have an idle circuit at all, or the idle adjustment screw is just not doing its job.

    I am fairly certain I would have noticed a missing O ring on the mixture screw on reassembly, so I'm confused about where that went. I looked in the passage and it looked like there was no room for the rubber to be in there.

    Is there ANYTHING I can try before taking the carbs back off? If I take the carbs off, what exactly am I looking at fixing?

    I had to take off the throttle butterflies to oil the felt washers on the throttle shafts, and maybe I installed them in some way where they are blocking the idle passage? Like they're on the wrong side? That's all I can think of, but I don't know if that's possible.
    1975 CB400 F0 Stock
    1974 CB550 K0 Chopper
    1970 CL350 K2 Stock

  7. #6
    Sensei 66Sprint's Avatar
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    Have you tried re-setting the idle to 1200/1300 once the engine has warmed up?.......
    Last edited by 66Sprint; 06-08-2019 at 04:04 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

  8. #7
    Senior Member jakec's Avatar
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    I have maxed out the idle adjustment, so i would think it would be in xcess of 1200 rpm once warm (and I have had it warm).
    1975 CB400 F0 Stock
    1974 CB550 K0 Chopper
    1970 CL350 K2 Stock

  9. #8
    Sensei 66Sprint's Avatar
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    Fuel level NOT reaching idle circuit jetting or idle circuit blockage........

    Are the mixture screws at the factory standard starter settings?.....
    "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

  10. #9
    Senior Member jakec's Avatar
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    Yes, they are set at 1 out to start (manual 1-1/8 out)
    1975 CB400 F0 Stock
    1974 CB550 K0 Chopper
    1970 CL350 K2 Stock

  11. #10
    Senior Member Rob Axel's Avatar
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    How was it running BEFORE you tore into the carbs?
    Is the timing set proper? Shot in the dark?
    I do know it doesn't take a whole lot to clog those jets
    "Yes, my hands and nails have grease stains. I ride vintage!"
    -xulf13-

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