K1 K29A carburetor vs K1 replacement carburetor?

Good evening all,
I was looking for a rebuild kit for the carburetor on my K1 and found no markings for identification of the carburetor on my ol'red k1?

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All the information I can find says that (pictured below) this is the carburetor that the bike came with. My main concern is are these two carburetors interchangeable on the manifold that is on my bike now? If anyone has any information it would be greatly appreciated.
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Tripod

Active Member
You have a repop china carb there. The ct90 k1 came with either a t90ka (oddball four screw) or a k29a (two screw) keihin carb. Finding a rebuild kit for what you have will be hit or miss.

Swapping a replacement carb like you said is just a matter of getting it to mate up with the intake manifold spacing.

The replacement carb you posted a picture of is for an st90. It has a different choke lever than a ct90. It will work if you dont plan on riding with the frame plastics that go over the neck of the frame.

Dratv has a good section on Ct90 carbs and available replacement parts. Are you familiar with his site?
 
Hi Tripod,
I pulled the carburetor off today and took some measurement and pulled the bowl off, cleaned it and checked the float valve. The valve is shot. The tail tell ring on the half way down the sealing area. So it's shot.
Yes I have frequented DrAtv website. Great site!! Thanks for suggesting it.

I don't know the measurements of the carburetor mounting flange pictured in the bottom two photos if anyone does I Would appreciate knowing what they are?

On the intake manifold on lil'Red and the carburetor on it are as follows.

Outside of the mounting bolt holes:
2 1/8" or 28.575mm

Inside of the mounting bolt holes:
1 5/8" or 41.275mm

Center (intake) hole:
13/16" or 20.637mm

On the DrAtv website it appears that the carb they sell doesn't come with jets.

https://ct90restoration.blogspot.com/2017/10/adjusting-and-jetting-ct90-carb.html

This page listed above says that the K29A carburetor had #35 & #75 jets. The DrAtv didn't have a jet as low as a #35?

Not sure what the current carburetor jet sizes are the jets are unmarked. Lil'Red red runs, drives and starts great so not sure if I Would be interested in changing the jet sizes.

Any advice Would be greatly appreciated I am kinda stuck at the moment.
Either I buy another China knockoff and hope the jets interchange if not the same size. $28.00 Ebay
Or
Buy the DrAtv without jets and without knowing if it will actually fit the manifold.
$59.99 + jets if I can find the lower #35.

Thanks to Tripod and anyone else who has taken a interest in this post.
 

Clayton

Active Member
I have been down this road before my friend, it’s super hard to find a replacement carb that lines up perfectly with your original plastic parts. Ether the down tube cover doesn’t wanna fit or the boots don’t fit or the mounting holes for your air box don’t line up. I ended up using a carb that looks exactly like the one in your first pic. I had to buy the “carb to air filter box” boot for a CT110 for it to fit on the carb correctly. I did end up having to sand down the end of the air box a little bit so my mounting holes would line up on the frame. Iv attached a pic of the part I sanded down. This isn’t the air box I sanded it’s just one I had sitting around. I’ll try to post the parts I used if I can find them again lol. I did buy everything from DRatv though. You do have to be careful when you sand this down because you are making the end cap bolt longer wich means if you go to far the end cap won’t seal right.



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Hi Clayton,
Thanks for your post. Luckily I don't have a air box or a air intake hose. I am running without the downtube cover. I am running just a pod filter that attaches to the carburetor.
I am wondering if the carburetors pictured will interchange on the same k1 manifold. It Would be nice to have a stock style k1 late two screw carburetor with a 6,000 adjustment knob.
I am thinking it will mount up okay with a tube nipple Modification and hopefully the pod filter will mount on the new style carburetor.
Thank you for your time and Intel. I will certainly come back to your post when I get the money to get the downtube cover and stock air filter box set up.
Thanks again Clayton.
 

b52bombardier1

Well-Known Member
To get some of these "almost correct" Chinese carbs to fit the original air filter, I've had to resort to making a spacer that fits between the manifold output and the carb throat input. These carbs are often too short from front to back and some kind of extension is needed to reach the air cleaner.

I've made these spacers out of hockey puck rubber and had them 3D printed in a fuel and heat resistant printing filament.

Rick
 
Hi Rick,
It says it's made in Taiwan so won't know till it gets here. Luckily I am using a pod type filter on it and for the time being it doesn't have a downtube cover.
The air box, filter, mounting hardware and downtube aren't to cheap so that will have to wait for awhile.
 

Tripod

Active Member
You will need a k2+ intake manifold if you are swapping out a four screw carb. The four screw intake is offset at an angle while the k2+ is almost parallel with the ground.

And a new isolator and gaskets.
 

Clayton

Active Member
My K2 when I got it had been pieced together with lots of different model parts. My original down tube cover would not fit because it was hitting my carb top. I assumed it had the wrong intake pipe and looked online to find a K2 replacement. I found one on Ebay. Honestly I could not see the difference or find a good way to measure the difference but the new one worked perfectly. So if you need a later model intake pipe Iv got one if you need it NWMissouriCT90K1
 
My K2 when I got it had been pieced together with lots of different model parts. My original down tube cover would not fit because it was hitting my carb top. I assumed it had the wrong intake pipe and looked online to find a K2 replacement. I found one on Ebay. Honestly I could not see the difference or find a good way to measure the difference but the new one worked perfectly. So if you need a later model intake pipe Iv got one if you need it NWMissouriCT90K1

Hi Clayton,
Thank you I will definitely let you know if that is needed. I just ordered the carb, a jet, carb insulator and O ring.
I will keep you and everyone posted on the progress as soon as the carburetor and other stuff come in.
 
Hello all,
Just a update. Got the dratv replacement carburetor today. I will take measurements for everyone tomorrow. The attached photos show a comparison between the old carburetor, old carburetor's air filter and the new carburetor.
I must say I was a little disappointed to see the screen on the replacement carburetor is pushed in and mangled a bit.
Oh well for the price if I can get it to work I will be happy.
The mounting holes look to be the same distance apart, but the intake side hole on the replacement carburetor is considerably smaller.
On the filter side of the replacement carburetor is also considerably smaller. Small enough to require a different air filter.
At this point I half to say I am considering just buying a Chinese replacement carburetor like the one I pulled off. Ebay for $15 with a air filter included.
I will take measurements and share them with everyone tomorrow or the next day at the latest.

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Well didn't do measurements but did do a fit up. It looks like it might actually work. The bolt threads aren't the same. So I will need to take it to the hardware store and get some.
Not sure how to remove the throttle cable and reinstall to the new carburetor but I am sure I can figure it out. I will keep everyone posted with any new developments.
Thanks to all for your time and interest.


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Unbelievable ordered Thursday last week still hasn't left Philadelphia yet!! Nice job USPS!! Ordered from a company has had a good reputation In my book. I will never use the USPS again!! The worst possible service. Almost 6 days and has yet to leave town. Bravo USPS bravo.
 
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