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Crosspost: CT2 Top end with new VM26 carb

  • Billy Mild
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Crosspost: CT2 Top end with new VM26 carb was created by Billy Mild

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. 
28 Jul 2022 06:57 #1

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Replied by MarkT on topic Crosspost: CT2 Top end with new VM26 carb

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. 
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
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28 Jul 2022 07:59 #2

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Replied by Billy Mild on topic Crosspost: CT2 Top end with new VM26 carb

I wish I could use the stock carb, but the float bowl is cracked. 
28 Jul 2022 08:06 #3

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Replied by AirborneSilva on topic Crosspost: CT2 Top end with new VM26 carb

Have you thought about JB weld?  might be possible to fill the crack...
2023 Tenere T7
1976 DT400C
1975 DT400B
1973 RT3
1981 DT175H
1980 GT80
1972 CT2
28 Jul 2022 10:26 #4

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Replied by Sneezles61 on topic Crosspost: CT2 Top end with new VM26 carb

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
28 Jul 2022 12:52 #5

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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."
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Last edit: 28 Jul 2022 13:35 by JayB. Reason: Added a sentence.
28 Jul 2022 13:25 #6

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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.
Last edit: 28 Jul 2022 13:43 by JayB. Reason: Added a sentence.
28 Jul 2022 13:39 #7

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Replied by Swoop56 on topic Crosspost: CT2 Top end with new VM26 carb

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 .
 
28 Jul 2022 15:03 #8

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Replied by Billy Mild on topic Crosspost: CT2 Top end with new VM26 carb

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.
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29 Jul 2022 09:15 #9

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Replied by MarkT on topic Crosspost: CT2 Top end with new VM26 carb

CT1 never had a VM26
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
29 Jul 2022 10:03 #10

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