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Discussion Starter · #1 ·
My dad and I are working on a 1981 Cm400A recently bought a pair of VB24A
carburetors to replace the original ones which were broke. I have been looking for a rebuild kit to go though the thing, and poking around here I have herd aftermarket ones may not have the right jet sizes or vary otherwise. Though it was easy to find listings for individual OEM parts, I have not found a full OEM kit. Does such a thing exist and I am missing it?
 

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I can't remember ever seeing a complete rebuild 'kit' from Honda oem but wouldn't recommend getting aftermarket kits unless you like doing the carbs many times over. I would get the individual pieces by starting with the o-ring/seal kits from Honda and going from there.

Welcome to the forum.
 

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Go to your local Honda dealer, see if they can get you the gasket set, part number:

16010-448-305


If not just Google the part number, you'll find plenty of sources.

If you need the float valves check this part number:


VALVE, FLOAT
16155-413-751




The problems with aftermarket kits are a lot deeper than just having the wrong jets, many of the other parts just don't fit right and are unnecessary since you should not need any of the hard parts with the possible exception of the jets and then only if they are the wrong size.

Your 81 24C carbs should have 68 primary and 112 secondary jets. Even if the carbs are trash the jets may still be OK.

Your 24A carbs could have either 72/105 or 65/110 jets.

Personally, I would start out with the 72 primaries and 112 secondaries from the carbs that came with your bike. You'll have to get it on the road to determine if any further refinements are re
quired at which time individual jets
are plentiful.

Welcome to the group. Got any pictures of the bike?
:p
 

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Honda sells the soft parts as a kit 16010-417-305
In addition you will need air cut valve diaphragms and float needles. These pieces can be aftermarket since you have the adjustable floats in these carbs.
There should be no need to replace the jets unless they are damaged. It's usually recommended to increase the primary main jet one size to correct the inherent lean condition the bikes were built with.
Here's one of many dealers that sells at a discount Hammond Indiana, Honda, Yamaha, Kawasaki, Suzuki, Sea-Doo, Can-Am, Polaris, Ski, Tucker Rocky, Parts, ATV, Motorcycle, UTV, Accessories, Apparel,
 

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Discussion Starter · #5 · (Edited)
here are some pictures of the bike as it is today. tank is off as its been sandblasted for paint.
also pictured is the aftermarket exhaust that came on it. Will it affect the carburetor tuning any?

CM400A_0211-Tank_blasted.jpg CM400A_0214-Exhaust.jpg image1.JPG
 

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Exhaust changes often require jet changes. Since the original primaries for your bike were 68s, a one size increase as is commonly recommended would be to 70. Going up one more size for the mufflers would get you to 72s which just may be installed in your 24A carbs. If not, they're not hard to find.
 

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Looks like they might be actual mufflers (as opposed to "pipes"). And (I am not sure about these things, but...) the overall exhaust length does not looks to be substantially shorter than stock (which might change things more than a little). I can't tell from your pictures, does that exhaust still have the crossover piece (which is more than just a simple "H" pipe - search the forum for "power chamber" - and helps give the system some of the characteristics of both a single and a dual exhaust, for decent power at a wider RPM range)?

Regards,
 

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From the picture I'd say that it's just different mufflers since the heat shield is still in place and attaches to the power chamber.
72 jets should be sufficient
 
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