1975 Honda CB 125 HELP!
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1975 Honda CB 125 HELP!

This is a discussion on 1975 Honda CB 125 HELP! within the Technical forums, part of the Caferacer.net Forums category; Ok so I inherited this bike and it is a great starter for my kiddo's. However it runs like crap I have replaced everything but ...

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  1. #1
    Junior Member Thickshady's Avatar
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    1975 Honda CB 125 HELP!

    Ok so I inherited this bike and it is a great starter for my kiddo's. However it runs like crap I have replaced everything but it still spits and sputters when it warms up. And no matter how much I tinker with the points and pulg or even the carb it still will not Idle. Any help is appreciated! TS,

  2. #2
    FR
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    Did you replace the points and condenser, or just tinker with 'em? And what level of tinkering did you attempt with the carb? New jets and gaskets? What condition is the carb manifold in? (the rubber boot between the head and the carb) If it's cracked or leaking, you'll have these problems.
    Most of the time, to get a proper diagnosis of a running problem you have to go through the tune up steps in a methodical way, to eliminate the obvious problems. If you have the original manual it will give you those steps.
    Good luck!
    FR


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    Senior Member jaguar's Avatar
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    is the float set right in the carb? all pasages clear?
    after it is warm is it running fine?
    spudders at idle or in gear while riding?
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    Senior Member whiskeysid's Avatar
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    Does it have the original exhaust? I've found that the tuning on these small Hondas can really go to hell with a different-than-stock exhaust installed.
    -the Rad Baron
    -\'72 CB350
    -\'72 Kawasaki H1
    -\'72 Yamaha R5/RD350 hybrid
    -\'77 XS650
    -\'47 Harley U flathead
    -a bunch of other old Jap bikes

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    Senior Member jaguar's Avatar
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    how so? i have a straight pipe on mine.
    I am Derby\'s Bitch


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    Junior Member Thickshady's Avatar
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    Ok, So before you start laughing at me too hard here it goes. First I had no set needle in the Carborator and just prior to finding out this I was screwing around with the points. Now that I have a float set needle I bet it will run fine. But now since I screwed with the points and obviously have no idea how to gap them. I cannot even get it to start. I have a gap gauge and the setting calls for .014 but I do not know how to get the little basterd back in to time. TS

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    FR
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    What's your reference? The owners manual or repair guide should explain the steps. In short, you set the points gap first by adjusting the base position. Then you adjust the points timing by rotating the plate in relation to the points cam opening with reference marks on the flywheel. I use a very thin piece of paper between the points to determine when they open, because I don't have a timing light.
    FR


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    FR
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    What's your reference? The owners manual or repair guide should explain the steps. In short, you set the points gap first by adjusting the base position. Then you adjust the points timing by rotating the plate in relation to the points cam opening with reference marks on the flywheel. I use a very thin piece of paper between the points to determine when they open, because I don't have a timing light.
    FR


    http://sidewaysnortheast.blogspot.com/

  10. #9
    Senior Member whiskeysid's Avatar
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    quote:Originally posted by jaguar

    how so? i have a straight pipe on mine.
    I'm sure there are exceptions. I have a '75 XL125 was was the nicest running bike you could ride, but the ratty original exhaust eventually fell off and I replaced it with an aftermarker muffler. The bike hasn't run right since. I've tried to retune the carb a dozen different ways to no avail. I have a '70 SL100 with a non-original exhaust and it's the same story. I'm sure the tuning can be fixed, but so far swapping jets isn't making enough difference.
    -the Rad Baron
    -\'72 CB350
    -\'72 Kawasaki H1
    -\'72 Yamaha R5/RD350 hybrid
    -\'77 XS650
    -\'47 Harley U flathead
    -a bunch of other old Jap bikes

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    Senior Member whiskeysid's Avatar
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    quote:Originally posted by jaguar

    how so? i have a straight pipe on mine.
    I'm sure there are exceptions. I have a '75 XL125 was was the nicest running bike you could ride, but the ratty original exhaust eventually fell off and I replaced it with an aftermarker muffler. The bike hasn't run right since. I've tried to retune the carb a dozen different ways to no avail. I have a '70 SL100 with a non-original exhaust and it's the same story. I'm sure the tuning can be fixed, but so far swapping jets isn't making enough difference.
    -the Rad Baron
    -\'72 CB350
    -\'72 Kawasaki H1
    -\'72 Yamaha R5/RD350 hybrid
    -\'77 XS650
    -\'47 Harley U flathead
    -a bunch of other old Jap bikes

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