CT90 Carb Overview & Rebuild Tips: Fixing no idle off choke

This carb is the 78-79 round bowl version, but it is fairly similar to the earlier year carbs. And much of the info here is applicable to any carb.
Specs for both carbs are given at the end of the video. Thanks for watching!

[@fizzystream8868]

thanks for the video, gonna tear into my carb for my 73 and 74 later today. first carb i will have ever taken apart

[@danrutherford3882]

Thanks for a great explanation on this. Will try mine tomorrow 😮

[@tominmo8865]

Excellent explanations! Very helpful.

[@robwinters6097]

Great Job 👏 👏👏thanks for sharing! I just bought a 1970 CT-90 and am having the same issue you had 😮 so I will be cleaning the carburetor as you have🤩

[@troycotsenmoyer6736]

For your thank-you for your enlightening video I wish my carburetor had a fuel mixture screw but I don't think it does I'll check for that but you're right it doesn't want to run unless it's choked please confirm thanks again for your good enlightening video

[@themotofirm]

Even if there is no adjustment screw, there will still be a low speed circuit for it to get fuel at idle. There should be a low speed (idle) jet to manage this fuel, so either that and/or the tiny passage where that fuel goes is likely clogged. Spray through the idle jet and it should be coming through somewhere inside the carb barrel. Good luck.

[@georgelickemupwarren7639]

Im waiting patiently for the kit for my 78', Yatzu, and i didn't know about the C-clip open positioning. Thank you for this whole lesson Sir. Know of any original petcocks for sale?

[@themotofirm]

I don’t. I usually find em on eBay, or rebuild the old ones with oem parts

[@ninjaphlap]

Great video!!! What should I soak them in?

[@themotofirm]

Thanks I don’t typically dip, but you can try the Berryman chem dip, it’s not as gnarly as it used to be but worth using if yours is gunked badly.

[@barrel_rider8391]

Thanks so much dude! So where does the o ring go because I think mine is missing that! Also love the rat fink shirt man

[@themotofirm]

I assume you’re asking about the center emulsion tube/needle tube o ring and not the large intake seal o ring? The earlier tubes had little grooves in them for an o ring, so they seal when they thread into the carb.

[@barrel_rider8391]

@@themotofirm the center one yes! I think mine fell off or broke so I just need to know what size and where is goes!

[@themotofirm]

If your carb had one it’ll go in a little o ring groove on that tube. It’ll come with a rebuild kit, or you can use an o ring that is snug on the tube, and fits snug into the carb, as long as it’ll fit and seal.

[@isaackauffman5478]

Hey trying to find a rebuild kit for this same keihin carb with the round bole. Having no luck online. Any idea where I can find one?

[@themotofirm]

I typically find them on eBay. First choice is Japanese kits such as K&L or Keyster; here’s the Keyster I used: www.ebay.com/itm/274921727767?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=PE9UD81mRbm&sssrc=2349624&ssuid=przYOps-QBK&var=&widget_ver=artemis&media=COPY

[@davidkumeroa2997]

Cheers.

[@troycotsenmoyer6736]

I have a ct110 new carb. It appears to be identical. Without an o-ring for the mix screw. My bike runs on choke but it dies when I give throttle. It's behaves worse off choke. I have a filter on the reserve fuel line plus the screen filter in the carb. I can't understand it getting stopped up. Nevertheless I'll have to clean it. My c-clip is on the 3rd notch how many turns open for the mix screw. Any thoughts? Again thanks for the insightful video greatly appreciated.

[@themotofirm]

Sounds like a similar issue to this bike. The filters will stop most dirt, but fine particulate will still get through. The low speed circuit is very small so it doesn’t take much to clog it up. Not sure on the turns, I’d imagine it’ll be close to the CT90. Ballpark the turns and get the idle circuit clear. Good luck

[@wienus86]

So there is a golden little piece there next to the main jet. Where does that go?

[@themotofirm]

Took a while to figure out what you meant, I assume at 3:32? That is the needle jet, basically a guide for the needle, and makes the hole visible from the inside when you’re lowering the needle down into place. It presses lightly into the carb body from the bowl side, before the main jet and jet holder go in. Countersunk (tapered bore) goes toward the needle. I don’t typically mess with them since they don’t do much and don’t really go bad, but maybe I replaced this one since the kit had it, not sure.

[@edwardgolonka-jd4sc]

That's true dat any 🔗 s to specs on rebuilding float level etc? thx

[@themotofirm]

Float level was non adjustable on mine (plastic). It should look roughly parallel with the gasket surface. If it’s not/damaged, replace it.

[@shanepipkin4041]

my 90 atv honda has round bowl and plastic float do you think this one will work and be better?

[@themotofirm]

If it bolts up it’ll likely work, not sure it’d be “better” though.

[@edwardgolonka-jd4sc]

That true dat

[@edwardgolonka-jd4sc]

As sensitive as a gas weeder carburetor lol