New carb for 1979 ct70

Discussion in 'Tech Area' started by Eric D Westall, Oct 29, 2019.

  1. Eric D Westall

    Eric D Westall New Member

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    I have a barn find 1979 ct70 that is pretty beat up, but I love it and sort of want to keep it original. No concourse here. It's on my second Resurrection, this time from my garage after 15 years.

    It needs a new carb. I see all of these aftermarket choices, but I am running into size problems. Here are the dimensions I have on mine:

    Air Filter outside dimensions 31mm
    Bolt to bolt 38mm, center to center
    Intake 14mm ID

    I can't find anything ct70 related to this.

    We are on a time rush here. Need to use it to run to the grocery store to get beer. Help!
     
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  3. kirrbby

    kirrbby Well-Known Member

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    Honda changed up the carb and intake in 78 I think. The bolt spacing at the carb to manifold changed...I imagine that is the intake that you have, and it's not as common as the earlier style/size. If you source a early type CT70 intake, you'll likely find a carb much easier.

    You might just clean and rebuild your old carb?? Is it too far gone?? A aftermarket carb might not work with the stock airbox.
     
  4. racerx

    racerx Administrator
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    I'd source a hondatrailbikes K0-style reproduction carb. And, if necessary, the K0-style intake, if needed to make it fit the airbox. The early style, rectangular-bowl, carbs...used well into the late 1970s...are DIY & tuner friendly.
     
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  5. Eric D Westall

    Eric D Westall New Member

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    I think I have rebuilt it once and I can probably get it running, but my choke spring is sort of shot. From what I have read and seen, rebuild kits don't come with choke parts. I have seen that I would have to buy an aftermarket and scab parts from it, adding to my rebuilt carb. I also saw in a post in here that the dimensions of my intake looks like the size used on the 50cc motors. I confirmed I have the 72 cc motor and started thinking maybe somebody put a carb from a z50 on here, but then that was after hours of scouring websites with no answers...mind starts racing.

    Are yall recommending I buy an original? Looks like some of the aftermarkets are getting decent reviews. I started searching for a new manifold and didnt find anything on beatrice, but if a new manifold and a new aftermarket carb with air filter would do the trick, I would be good with that. This poor thing has xr75 brake shoes (found them in my garage from waaay back and surprised they fit), an xr 75 brake handle, some gear shift from who knows what bike and a CB350 rear shock on the left side only. (It was bottoming out in my backyard dirt track). I even made the vinyl seat cover. So, aftermarket here and there ain't gonna hurt her. She is a true gem. Don't judge!!
     
  6. Tripod

    Tripod Active Member

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    RacerX hit it on the head. The original PB37 carb isnt very user friendly. You can source a chinese carb, but its a roll of the dice as far as quality and fitment.

    I have the original carb on my 79 and if it were to crap out what I would do is source a K0-77 carb and intake off ebay plus a rebuild kit.
     
  7. racerx

    racerx Administrator
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    Several options here...
     
  8. allenp42

    allenp42 Well-Known Member

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    Not all that familiar with the carbs used on 78 and above, but are you talking about the spring on the choke flap? I found a choke flap in my junk box. If this will work, you're welcome to it.
     

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  9. racerx

    racerx Administrator
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    I believe he's talking about the externally-mounted "watch spring" used with the later, round-bowl, carbs. It lives under the black, plastic, cover shown in this pic
     
  10. Eric D Westall

    Eric D Westall New Member

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    Yes, correct, wound watch spring style. Controls the float tab. Trying to remember several years back, I may have been dealing with jet clogging issues. I am at a fork in the road here, so I think I am going to order a rebuild kit and see what that does. One step at a time.

    Thank you everyone for your input and assistance. I am committed to get her back on the road.

    Found all the rebuild items needed on dratv, including the $37 choke spring! $80 rebuild kit. Love it.
     

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