Niche has diagrams, dimensions, and pictures of Mikuni float valves. You'll have to compare yours if you go the route. I don't remember the number.

RMATV-MC has the parts. They ship super fast in my experience. I already gave you the gasket part number but you might have to look up both parts by model. www.rockymountainatvmc.com/

1970 Yamaha CT1b needle and seat


1971 Suzuki TS185 float bowl gasket, same as 1970 CT1b.

The very cheap Chinese Mikuni copy carbs are poor, and difficult/impossible to tune.

Nibbi, Chinese Keihin copies are very nicely made, easy to tune and set up, and probably going to cost about the same as fitting new parts to a 50-year-old OE carb.

yamfan wrote: "Nibbi, Chinese Keihin copies are very nicely made, easy to tune and set up, and probably going to cost about the same as fitting new parts to a 50-year-old OE carb."

Possibly true on some bikes.  Have you ever tried to install one on a CT1?  If so, can you do a write-up on how you dealt with the flange mount, any cable issues, challenges of getting the stock airbox to mate with a new carb?  Jetting specs for the conversion?  All the parts needed and their cost? 

Might be the best thing ever...  but until someone has actually done it, in my experience the swap is likely to be far more trouble than it's worth in time and cost.  Stock carb runs great on these models and rarely go completely bad.  And it's a piston port so messing with the intake tract tuning even slightly can affect the power.  Plus this old a bike will likely retain far more value without a counterfeit Keihin installed.  Just my experience, opinion, and advice.

I bought a no name $25 Chinese carb for my at3 and it worked pretty good. It's a gamble though because there's no way to tell which ones are complete garbage.

​​​​As noted by other people, you lose the ability to tune it and they aren't high quality. ​I would have repaired my original carb if I could have but it was too far gone.

I had fuel overflowing issues with my DT.  The previous owner says he fitted a new needle valve, which he had.

I gave the valve a quick lap in and adjusted the float height.  Same result.

I bought another needle set and readjusted the float height.  Same result.

I lapped in the new valve and set the flat height to max.  Same result.

Paranoia kicks in....  It is the devil bike after all.
Those are solid floats so they cannot be flooded with fuel.  They however may have become saturated internally and no longer bouyant enough to shut off the valve with enough force.
Alternatively those floats were designed with denser leaded fuel in mind, could this have a bearing on the problem?

Dunno.  I did not trust those floats however.

I took a punt on a cheap £20 chinese mikuni copy to see if the floats would fit my original carb as genuine mikuni parts are hard to find in the UK and extremely expensive.  I think the floats I came across were in the region of £80.

The chinese floats were identical and what is more, the float valve was teflon tipped.  Both fitted in my original carb just fine.  Problem cured.

That is as far as I was going to get.  Adding cheap non original units to a bike built to be factory fresh is a performance gamble, a devaluing factor and likely could cause no end of other problems.

Other part I tried was the choke plunger.  Did not fit.  About 2mm too short.

Chinese clones are a crapshoot.  Are you prepared to roll the dice?  The only time I would consider trying one is if I bought a bike missing its carb and could not find a good used replacement



 

Flange to spigot mount adapters are easily available, and provide the advantage of having a rubber mounted carb, which reduces vibration and heat.

If running and performance are less important than original appearance, it's certainly possible to fit new parts to a 50+ year old OE carb, which will make it quite a lot better.

A new Nibbi PE or PWK copy, correctly jetted, will work a good deal better than either a rebuilt OE carb, or a cheap Mikuni copy, though. In terms of quality, they aren't far away from genuine Keihin.

Thanks for answering my question yam-fan/yamfan. 

Maybe someone will actually take a trip down the rabbit hole someday and find out the true expense in parts cost and effort it takes to install a counterfeit Keihin onto a CT1... 

....if they don't give up due to frustration and sell the bike before they complete the installation.