Getting a CT110 Carb on an ST90

Discussion in 'CT90, CT110, ST70, ST90 Discussion' started by Shamrockwill, Oct 11, 2018.

  1. Shamrockwill

    Shamrockwill Member

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    A while back I bought a CT110 Carb from DRATV to put on my ST90 after I installed the big bore kit and performance camshaft also from DRATV. I quickly found out that the boot that goes from the airbox to the carb would not fit on the new larger carb. I emailed DRATV about this and here is our exchange.

    -Me: Hello. I am going to install your big bore kit and high performance camshaft on my 1974 ST90. would the OEM CT110 carburetor you sell be a good choice to run with those upgrades? If not, what carburetor would you recommend using on an ST90 with the big bore kit and performance cam? Thanks. -Will

    -DRATV: that would be a great choice
    i don't know if the jetting is correct, but it should be very close if not
    thanks
    jack

    -Me: Hello. I went ahead and bought the OEM CT110 carburetor. What intake manifold and carburetor insulator do I need to make the OEM CT110 carb fit on my 1974 ST90?
    Thanks. -Will

    -DRATV: what are you going to do about the air filter ? do you want to keep using the stock one ?

    -Me: Yes Id like to keep using the stock air filter if possible? -Will

    -DRATV: then you must use the stock manifold and try to rig up something to adapt the larger rear of the new carb to the smaller hose coming from the stock air box

    -Me: Any suggestions on how to do that? -Will

    -DRATV: not really , sorry

    -Me: Would one of your carb to air box boots do the trick? like 17E or 42C? -Will

    -DRATV: Sorry i don't have anything on hand that will reduce it

    Does anybody know how I can "rig up something" or is there someplace that makes custom airbox to carb boots?

    Thanks,

    -Will
     
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  3. kirrbby

    kirrbby Well-Known Member

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    I'm thinking you can rig up something easy enough with a piece of rubber hose. The trick will be in making it look good. You might find a cheapo, generic, air filter with a good lookin boot that will fit your carb...then mate that boot to your original boot, or right to your air box..?

    Pics and dimensions will help a lot, so folks can see, and know, what you're working with.
     
  4. b52bombardier1

    b52bombardier1 Well-Known Member

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    I can send you a 3D printed spacer in PLA material between the exit of the manifold and the entry throat of the 110 carb. If you can find the same spacer for a 72 Honda CL100, our 3D printed spacer is modeled very closely after that spacer. My oldest son is big into 3D printing and this was the first ever part that he modeled and printed for me. Since then, he has done a throttle cable clip on my LS-engine equipped 70 Chevy El Camino. Cost for the carb spacer to you . . . . zero.

    Not sure but the spacers below might work. You'd have to ask the vendor about the width of the mounting post holes.

    https://www.ebay.com/itm/1965-Honda...d4e6310:g:7QEAAOSwOLVbR60n:rk:17:pf:0&vxp=mtr


    https://www.ebay.com/itm/HONDA-1972...03ce7fa:g:nd4AAOSwytJZ7MkE:rk:29:pf:0&vxp=mtr

    This same spacer can be copied in genuine NHL hockey puck rubber. The rubber has good squish properties for no vacuum leaks, resists heat and gasoline fumes.
    Rick
     
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  5. Shamrockwill

    Shamrockwill Member

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    Well I can't say no to that offer. I'm not familiar with exactly how a spacer would work and I can't quite make it out from the pics in those links but I'm sure once I have one in my hands it will become apparent. Where would I take it to be copied in hockey puck rubber?
     
  6. Shamrockwill

    Shamrockwill Member

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    Here's some pics of the situation. I have a CT110 carb boot as well. It and my original ST90 boot are pictured here. I was thinking of cutting the two boots and melding them together to create a Franken-boot that would fit correctly on the air box and the carb. Would 3M weather stripping adhesive work to hold my Franken-boot together?
     

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  7. Shamrockwill

    Shamrockwill Member

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    Oops here's the rest of the pics. I would cut the boots first before I meld them but this is just an example of how it would work. MVIMG_20181013_185825.jpg MVIMG_20181013_185742.jpg MVIMG_20181013_185748.jpg
     

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