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CB400N 1981 Keihin VB31B jets

CptCaveman

Member
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May 4, 2021
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Location
Nimes, France
Hi all,


I'm relatively new to tinkering with bikes. I have a CB 400 N from 1981 that I'm working on. I believe the carbs are Keihin VB31B. I'm looking at getting a set of jets to play around but am a little confused regarding the terminology. There are lots of sets on ebay along these lines: "for Keihin PWK PE OKO KOSOO" or "OKO CVK" etc. What do all these acronyms mean? What should I be looking for exactly?


Thanks in advance!

Edit: I've had a look at the stickies but all seem to be dealing with VB21, VB22 and VB24 carbs. Cmsnl.com as mentioned in some of these stickies doesn't help because it just gives part numbers but no information that help you identify the correct replacement jets.

Any help would be greatly appreciated.
 
ancientdad said:
I'm surprised you didn't see this sticky thread by LDR at the top of the very section you posted this in. Jim breaks down the carbs for the SOHC 400 as well as anyone, everything you need to know should be here.

https://www.vintagehondatwins.com/forums/showthread.php?64-Carb-Information-Years-Jetting-and-More
Click to expand...

Thanks AD... I did look through that thread, but since I have a VB31 Carb, the following applies to me:
There are VB31, 32 and 34 versions used elsewhere in the world but they all work the same as their US counterpart. Use www.cmsnl.com to find offered jetting for year/model if not listed here.
Click to expand...

I looked it up on www.cmsnl.com and when you look at the relevant nozzle sets etc, they don't provide any details that would allow you to find the rights parts on ebay.

The difficulty I am having is finding jet sets on ebay that are compatible with my carb... e.g. what do "PWK", "PE", "OKO", "CVK" etc. all stand for and how do they relate to my carb?
 
CptCaveman said:
The difficulty I am having is finding jet sets on ebay that are compatible with my carb... e.g. what do "PWK", "PE", "OKO", "CVK" etc. all stand for and how do they relate to my carb?
Click to expand...

I'm not sure what some of those abbreviations are referring to, but I do know that PWK is a KeiHin reference and not likely to do with your carbs. The part in the sticky I saw and thought would help is this:

VB31 carbs for non USA models
VB31 F carbs (32mm venturi), jets, primary #72, secondary #110, idle #35

And with that you should be able to go to JetsRUs and get what you need. I wouldn't buy jets from an eBay seller without knowing for sure that they actually know what they're selling, which many eBay sellers do not. If that doesn't help, Jim will be along later (he's on the west coast as I'm sure you realize) and he'll know.
 
JetRUs is a great resource but unfortunately they will only ship to the US. This baffles me but nothing you can do about it. I have had parts shipped to my buddy in Washington who then forwards them on to me in the mail. Could be a problem for you as I see you are located in France.

Ironically I was looking the JetRUs website this morning to see if the shipping policy might have changed recently and it has not.
 
I've never ordered from them so I was not aware of that, and it is unfortunate. Hopefully he can find a workaround similar to what you mentioned.
 
These are the Primary and Secondary main jets https://www.jetsrus.com/a_jets_by_carburetor_type/jets_keihin_99101-393_main_round_28-xxx.htm
I believe these are the idle/slow jets https://www.jetsrus.com/a_jets_by_carburetor_type/jets_keihin_N424-26_slow_36-xxx.htm I don't have any of the screw in versions to check measurements unfortunately.
To order the main jets from Honda the part number would read as 99101-393-????.
#100 and over will be 1??0 with the last 0 as a .5 measurement IE: 108.5 is 1085 and 108 is 1080
#99 and below will be 0??0 IE: 99 is 0900, 95 is 0950
 
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