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Discussion Starter · #1 · (Edited)
Hello

I have Keihin 722A KE carbs in my CB350 K4 1972 bike. Just rebuilt them with Keyster KH-1200F kit as it was mentioned to be for CB/CL350K2-4. Then I found this:

Carb model 3D, 722A, 726A, 728A

Float level 26.mm
Std main jet #68 primary (722A,726A) #70 primary (3D,728A)
Secondary #70 (3D,728A), #105 (3D, 722A, 726A)
Std slow jet#35
Idle mixture screw initial setting:
3/4 turn from closed (3D)
1 1/8 turns from closed (722A, 726A, 728A)
Idle speed 1200rpm.

KH-1200F kit have 70 for main primary instead of 68 as mentioned above.

1. How big is the difference? Can I just leave it there?
2. I guess main secondary (105) is the one where the needle goes into, correct?
 

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The 70 is about 3% bigger than the 68. If you bike has been running lean you might want to try the 70s, otherwise you can just use the old jets unless they are damaged. Aftermarket kits often include incorrect parts and most of the hard parts they come with are generally unnecessary.

The secondary jet is the one one with the needle (metering rod). While these can wear due to the movement of the needle I still wouldn't replace them on a bike that has been running well. Just because the new ones are marked as being the proper size doesn't necessarily mean they are.
 

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The Brass Jets do not wear, they only need to be cleaned and clear of any clogs.
Unless they have been abused by someone during disassembly you should only need to replace the rubber O-Ring parts. and the Float Needle & Seat.
 

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Honda still makes the O-Ring Kits for replacements.

Any Dealer can get them for you.

The sizes were never documented in any of the manuals. That I am aware of.
 

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I would guess the float level was set too high to 'compensate' for worn shut off valves (plus fuel not being switched off when parked?)
Personally I find 26mm works much better with todays E10 fuels
 
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