Stalling CB175 at idle - Page 2
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  1. #11
    Junior Member mtn_'s Avatar
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    Quote Originally Posted by lhemrick View Post
    Thanks for that info Simo! Question is what are my carbs mixture screws specified range? I've seen charts on this site with ranges depending on what type of carb. I don't know what I have because these didn't come with the bike and I see no numbers on them like all my 350 twin carbs do. Besides if I'm not running stock air cleaners and exhaust that range would differ anyway correct?
    Yeah, I meant to point out earlier that just different air and exhaust pressures and quantities will throw the mix off. If your carbs are close to stock, most manuals say from 1 and 1/4 turns out from full close for the gas and slightly less for air i believe as Simo pictured. This really will only help you if most of your features are stock. You have to sync the carbs and set the air/fuel ratio of each individually. You can back out the mix screw all the way but sometimes the carb needles don't seat all the way and could be part of your problem. I would run the bike on each cylinder at a time to properly gauge what is going on, as I said before. Your carbs should never leak gas, this is bad and means one is overflowing. 21mm is for the stock carb and may not be your correct float height. This measurement is also taken a certain way, with the bowls resting on but not pressing the gas float needle and measured for max depth then. Did you check to see if the gas float gets stuck when flicking the bowls up and down? very common.. no cold start means at least one carb is getting not enough fuel when the throttle is closed, or a gas float is getting stuck. using the choke these things fire right up when clean and synced up.
    mtn_

    1968 CL175 K0 project (long-term perfection)
    1969 CL175 K3 daily
    1970 CB175 K4 daily
    1972 CL175 K6 project (bore)
    1972 CB350 K4 project (frame)
    1969 CT70 K0 project (fuel/spark)

  2. #12
    Senior Member lhemrick's Avatar
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    Main 102 slow 38. One manifold has 644A on it the other has 313B. I'm guessing they should match!

  3. #13
    Senior Member Simo's Avatar
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    Quote Originally Posted by mtn_ View Post
    Yeah, I meant to point out earlier that just different air and exhaust pressures and quantities will throw the mix off. If your carbs are close to stock, most manuals say from 1 and 1/4 turns out from full close for the gas and slightly less for air i believe as Simo pictured. This really will only help you if most of your features are stock
    Im going to disagree with this the 175 carbs don't have separate gas and air screws. The idle set screw adjusts the air/ gas mix at idle by allowing more air into the idle mix, ( start at 1 1/4 turns from lightly seated) it's a pretty fine adjustment when the passages are clean, at around 2- 2.5 turns out the passage is as open as it can be so no further adjustment can be made with that screw.
    The other screw adjusts the height of the slide within the carb body.
    Just because the exhaust and intake aren't stock doesn't mean the stock settings won't get you idling at 1200
    ( its unlikely you'll get a smooth response across the rpm range, you'll get flats and misses at some rpm, but that's not the issue here)
    Leave the float height at 21mm, changing it changes All other adjustments and settings. You'll end up with no baseline to work from
    Last edited by Simo; 01-02-2017 at 01:19 PM.
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  5. #14
    Junior Member mtn_'s Avatar
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    yep i meant throttle and mix sure when i say fuel then air screw. just helps me identify them and hopefully help lhemrick. In my experience it's been much different adjusting the screws with aftermarket air filters on vs the stock boxes with filter covers and side covers. Just letting you know that the stock adjustments may need to be tinkered with.

    Again, be sure you are correctly measuring the floats, then test the bike on one cylinder to further diagnose your problem. Are both carbs having the same issue?
    mtn_

    1968 CL175 K0 project (long-term perfection)
    1969 CL175 K3 daily
    1970 CB175 K4 daily
    1972 CL175 K6 project (bore)
    1972 CB350 K4 project (frame)
    1969 CT70 K0 project (fuel/spark)

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