1979 CT70 - carb identification?

Discussion in 'Tech Area' started by Kansas Corey, Jul 17, 2018.

  1. Kansas Corey

    Kansas Corey Member

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    Hey guys - want to buy a rebuild kit, but I'm not 100% sure what I've got. Can you please help me with the proper name / model number of this carb?

    I assume it's original to the bike and it obviously says Keihin, but is it a "PB" or a "PB 37" or....

    Forgot to mention, if it helps, it has 2 jets, the larger one is removable, but the smaller one looks like a press-fit item.
     

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    #1 Kansas Corey, Jul 17, 2018
    Last edited: Jul 17, 2018
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  3. wanrep

    wanrep Active Member

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    PB37A, which would be correct for a '79.
     
  4. OLD CT

    OLD CT Well-Known Member

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    A rebuild kit isn't going to have the thing you need the most like, choke bits! You should buy a cheap pz19 and rob the choke parts and bowl gasket.
     
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  5. Kansas Corey

    Kansas Corey Member

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    Thanks guys! Unfortunately, seems like my standard process - Parts I need aren't readily available so I have to figure something else out...

    Actually, it didn't look terrible when I opened it up, but wanted to see about new gaskets mainly.
     
  6. racerx

    racerx Administrator
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    Looks verrrry similar to the `80-`82 vintage Keihins. However, the `79 does not have the limiter cap, on the pilot airbleed adjusting screw. That's a good thing, btw. I've never been a big fan of the later carbs but, that's changing. They tend to do a better job delivering consistent idle-to-1/8 throttle performance, meaning they improved the low-speed atomization...it matters more than you might think. I wouldn't retrofit an earlier model with one of these, the K0-K1 era Keihin carbs are a lot more user-friendly, especially when it comes to parts availability, including some very good repops.

    NEVC and Dratv are the go-to resources for carb rebuild parts. Along with the rubber parts, be sure to replace the fuel screen; it's the plastic thingy that looks like it was pulled from a spray gun. The one p.i.t.a. with this era carb is the petcock. It's easier to replace as an assembly. That turned out to be a sign of things to come, didn't it? If your skill set includes drilling & tapping (threading small holes) the packing can be replaced, it's the 4-hole version; the rivets have to be drilled (very carefully) then the holes tapped, for M3 or M4 screws.

    Cannibalizing a pz19 for the choke parts is very resourceful, not to mention cheaper than buying NOS pieces, if they're still available.

    Sounds like, potentially, a lot of busy work, when you could just source a new carb (repop, or pz19). However, I see most of the original irriditing (that rainbow-ish color) on the outside surfaces. That means the carb body casting is likely in similarly nice, oxidation-free, condition...i.e. eminently rebuildable.
     
  7. allenp42

    allenp42 Well-Known Member

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    I may have one but since I'm not that knowledgeable on 79 carbs, we may need to do some measuring to make sure. I'm attaching a pic of 2 new carbs that I acquired sometime ago. I think the one on the left is more likely to fit your needs:

    Left Carb: Chinese copy, "EMSTD" stamped on throttle body. Intake flange is 42mm center to center on manifold mounting, 71mm from flange to rear flange, ID of opening on on manifold mount ~16mm. New, never had gas in it. If it's a true copy, you may be able to use the choke parts and maybe some other parts as well.

    Right Carb: Don't think this is what you need, and not 100% sure what it's for. Choke lever is wrong side for a CT70. I believe it is a genuine Keihin Carb. p/n PB 76A. Intake flange is 48 C-C, I haven't broken the seal to see what size jets are inside. ID of the manifold flange opening is ~19.5mm.

    If we can confirm that one on the left will work, will gladly give you a deal.
     

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    #6 allenp42, Jul 18, 2018
    Last edited: Jul 18, 2018
  8. Kansas Corey

    Kansas Corey Member

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    Thanks everyone! Appreciate the responses and the support as I learn some of this stuff. I'll hopefully get back to the carb rebuild in the next week or so as I'm currently in the middle of some other projects. Once I dig in, we'll see what kind of shape everything is in. My hope is that with some new gaskets, the rest will clean up nicely. I'll post some photos as I go - thanks again!

    allenp42 - appreciate the offer - will let you know ASAP if I need to take you up on it - Corey
     
    #7 Kansas Corey, Jul 19, 2018
    Last edited: Jul 19, 2018

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