yamaha-enduros.com/index.php/forum/perfo...-top-end-bike#151798

I'm trying to figure out if I need to swap the slide and needle over from my original VM24 carb or try the slide and needle that came with the VM26 carb first. 

You're asking a question that can't be answered.

Not the same carb size or possibly design and the slide needle and needle jet work together as a set. 

Universal carbs come prejetted and often run "okay" out of the box.  You'll probably need to make some jetting changes.  All you can do it run it and see.

If you wanted "easy" then find a CT carb or jet your AT carb to match CT specs. 

I wish I could use the stock carb, but the float bowl is cracked. 

Have you thought about JB weld?  might be possible to fill the crack...

Just a passing thought…. Have you tried to put the new bowl on the old carb? I haven’t a clue… but you won’t either unless it’s tried… A simple 5 minute verification
Sneezles61

Be careful when mixing and matching carb parts.  Here is what I did 25 years ago to a perfectly good AT2 cylinder/piston by mixing and matching AT1 and AT2 carb parts.  I didn't take notes.  I think I used a fat AT1 needle with an AT2 carb and who knows what slide.  It ran great for 10 minutes or so until it went Blaaaaaaa with no compression at 40 or so MPH.  I kept the piston so I would not forget!

 

If it were me based on my experience I would push the MarkT easy button: "If you wanted "easy" then find a CT carb or jet your AT carb to match CT specs."

If you want to use the VM26 I would disassemble it and note every part in it.  See if it works and make jetting changes as necessary.  Keep notes every step and change along the way.  Start rich and try not to hole the piston like I did.

Make sure your timing and plug heat range are correct before you start.

If the only serious problem with your original carb is a cracked float bowl .
Someone here may be able to help with an AT or CT replacement .
It'd save you some trial and error tuning your new carb to suit your bike .
 

I don't think where the crack is on the float bowl is salvageable.

I was trying to mimic the AT1MX or CT1 VM26 carb settings. The needle and slide cutaway are different I believe.

My engine has cleaned up ports and reed valve from the rebuild I did 5 years ago. Used a trusted 2 stroke engine build. He did the build on my RZ350.

CT1 never had a VM26