VB22P Carbs for CB450SC Nighthawk

Jflava7

Jflava7

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I had my motor rebuilt a year ago, but the mechanic was unable to tune the carbs due to time constraints. I have tuned them multiple times so this was no trouble for me. I disassembled them and cleaned everything with an ultrasonic cleaner. I replaced my accelerator pump and a couple gaskets. Afterward, it ran well, but had a mid rpm range stutter. I was able to push past it only with aggressive throttle input. Someone with more knowledge of carbs than I took them apart a few weeks ago and reported pinholes in the air cut valve and badly scored slides, as well as a missing slide ring seal. It's amazing that I was able to run the bike for as long as I did!

All of that to say: My VB22P carbs are nearly impossible to find replacement parts for. The bike is rare enough already, and it seems the carbs are even more rare.

I need 1 of 2 things. Either a reliable source for obscure Keihin carburetors and parts, or info on the usage of Mikuni VM32s with pod filters for my bike. Thanks!
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I realize yours aren't exactly the same, but for informational purposes have you seen this thread? I'm sure LDR will be along later.

How to Rebuild the VB Carburetors

This is dealing with the VB22J carbs in particular but most of it applies to the VB21 and VB24 carbs. As everyone knows that has done these they are problematic to get right the first time at best so hopefully this will help you get there. In this case I'm dealing with VB22J carbs that have had...
www.vintagehondatwins.com www.vintagehondatwins.com
 
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ancientdad said:
I realize yours aren't exactly the same, but for informational purposes have you seen this thread? I'm sure LDR will be along later.

How to Rebuild the VB Carburetors

This is dealing with the VB22J carbs in particular but most of it applies to the VB21 and VB24 carbs. As everyone knows that has done these they are problematic to get right the first time at best so hopefully this will help you get there. In this case I'm dealing with VB22J carbs that have had...
www.vintagehondatwins.com www.vintagehondatwins.com
Click to expand...
I've definitely seen this one. It was a huge help last year when I was troubleshooting. My biggest issue is that I have no idea where to source OEM Honda parts from (jets, needles, etc.) or what aftermarket parts to trust
 
PS: I can see someone shoved a bolt where a float bowl screw should be. Signs this carb was really messed with. Don't bother with those Mikuni kits. Every vendor lies and say it's plug and play. It isn't. I don't care what the clowns on FB/Reddit say. It never works out right. The stock carbs are more than adequate, and you won't find any additional power by putting a Mikuni/Pods/K&N on these bikes.

Do not use aftermarket float valves ("needles"), do not replace the jets except with OEM, do not replace the needle jet/jet needle assembly. It is OK to use aftermarket air cut off valves, passage plugs and fuel accelerator pumps. The pump you'll have to trim the rod to fit and you will need a pair of calipers and very thin feeler gauges to set the gap. It's critical for performance or you will have a dead spot a bit past 1/4 throttle.

Since there's signs the carb has been messed with you may want to post pictures of the jets. Very likely someone put a bologna "carb kit" in it and replaced the jets which is bad.

SCI is in Canada and should have the aftermarket parts you need. Again, absolutely no aftermarket float valves. I promise you it will never run right if you do. It sucks paying $60-$70 USD for two measly pieces of rubber but it's 100% critical that you do so.
 
Your stumble sounds like the accel pump isn't working or only working on 1 carb.
The rarity issue is due to the 1984 model year, Canadian and European distribution only.
That said your carbs use the same parts as the 1986 USA CB450SC Nighthawk.
As Frank mentions only use the Honda float needles.
Here's the air cut valve needed https://4into1.com/air-cut-off-valve-honda-xl250-500-xr250-350-600-ft500-cx-gl650-cb1000c-cb1100f/ Honda part # 16048-MC9-761
I have some spare used parts I can send, piston/slide, caps, plastic stop ring, plastic stopper for slide, etc. if you want to continue with this set of carbs.
Alternative to this set are carbs from the 1978-1983 CB/CM 400/450 manual trans models. The VB21A, B or C and VB22A-G. The VB21's do not have or need the accel pump. All VB22's need the accel pump.
I would not go with the Mikuni carbs.
 
Maraakate said:
PS: I can see someone shoved a bolt where a float bowl screw should be. Signs this carb was really messed with. Don't bother with those Mikuni kits. Every vendor lies and say it's plug and play. It isn't. I don't care what the clowns on FB/Reddit say. It never works out right. The stock carbs are more than adequate, and you won't find any additional power by putting a Mikuni/Pods/K&N on these bikes.

Do not use aftermarket float valves ("needles"), do not replace the jets except with OEM, do not replace the needle jet/jet needle assembly. It is OK to use aftermarket air cut off valves, passage plugs and fuel accelerator pumps. The pump you'll have to trim the rod to fit and you will need a pair of calipers and very thin feeler gauges to set the gap. It's critical for performance or you will have a dead spot a bit past 1/4 throttle.

Since there's signs the carb has been messed with you may want to post pictures of the jets. Very likely someone put a bologna "carb kit" in it and replaced the jets which is bad.

SCI is in Canada and should have the aftermarket parts you need. Again, absolutely no aftermarket float valves. I promise you it will never run right if you do. It sucks paying $60-$70 USD for two measly pieces of rubber but it's 100% critical that you do so.
Click to expand...
Well, to be fair, some of that may be my bologna 🤣
But yes, I purchased the bike 11 years ago fully disassembled and in a box. I'm not sure who all touched it but things were quite messed with when I got it. I'll need to double check on the jets and needles for sure. Would it be wise to verify those, replace the air cut off valve and ring seat, and attempt tuning before trying to find the pistons and top covers?
 
LongDistanceRider said:
Your stumble sounds like the accel pump isn't working or only working on 1 carb.
The rarity issue is due to the 1984 model year, Canadian and European distribution only.
That said your carbs use the same parts as the 1986 USA CB450SC Nighthawk.
As Frank mentions only use the Honda float needles.
Here's the air cut valve needed https://4into1.com/air-cut-off-valve-honda-xl250-500-xr250-350-600-ft500-cx-gl650-cb1000c-cb1100f/ Honda part # 16048-MC9-761
I have some spare used parts I can send, piston/slide, caps, plastic stop ring, plastic stopper for slide, etc. if you want to continue with this set of carbs.
Alternative to this set are carbs from the 1978-1983 CB/CM 400/450 manual trans models. The VB21A, B or C and VB22A-G. The VB21's do not have or need the accel pump. All VB22's need the accel pump.
I would not go with the Mikuni carbs.
Click to expand...
That's a lot of great info! Thank you!
I suppose the accelerator pump could be the culprit, but that is one thing I'm confident I did well. I followed your cleaning guide and set it up accordingly last summer. The passages were quite gunked up, but I was able to clean them out with a good long bath in the ultrasonic cleaner.
I'll make sure my jets and needles are Keihins/Hondas and I'll get back to you on the parts. Thanks again!
 
This is a Canadian only bike model and carb set as you have discovered and no OEM Honda parts are available from any vendor anywhere. The main and slow jets may still be available from Honda. Honda Canada does have a parts fiche for this bike. Where any other online parts fiche isn't for this specific Canadian model in the USA or the European ones. This bike was never sold in Europe or USA. I have the same carbs on very clean and low kilometre bike, which had the same mid range stumble.
You will need the fix any worn or missing parts first and can possibly substitute slides and other pieces from comparable CV models. So either LDR or Frank may be able to assist you there.
I corrected the issue by shimming the needles on my P series and it is still somewhat lean but doesn’t stumble anymore. It could still benefit from some slight jet upsizing.

Ask LDR for suggestions on upsizing the jetting slightly from your stock sizes. These are a two jet only carb and not a three jet like others in this VB series.
 
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Jflava7 said:
That's a lot of great info! Thank you!
I suppose the accelerator pump could be the culprit, but that is one thing I'm confident I did well. I followed your cleaning guide and set it up accordingly last summer. The passages were quite gunked up, but I was able to clean them out with a good long bath in the ultrasonic cleaner.
I'll make sure my jets and needles are Keihins/Hondas and I'll get back to you on the parts. Thanks again!
Click to expand...
Did you actually extract the emulsion tube and idle jets? Many don't. Did you physically separate the carbs?

Not sure which you mean by "ring seat, and attempt tuning before trying to find the pistons and top covers?"
 
I also see a lot of boogered up and rounded off screws. The screws, float valves, and jets should still be available from Honda. If not, there are other places to source those.
 
Maraakate said:
Did you actually extract the emulsion tube and idle jets? Many don't. Did you physically separate the carbs?

Not sure which you mean by "ring seat, and attempt tuning before trying to find the pistons and top covers?"
Click to expand...
Frank,

Same issue I had on my P series VB carbs. They were only used on the one year Canadian 1984 CB450SC Nighthawk. There is no emulsion tube for the middle jet used in a regular VB series setup. They are a two jet only carb with a slow jet with an emulsion nozzle attached to the jet, plus the main jet emulsion tube on the slide jetting.
The ring seat is possibly the damper ring for the slide cushion used in the carb top section under the cap.
 
https://www.partzilla.com/catalog/honda/motorcycle/1986/cb450sc-a-nighthawk-450/carburetor - For 1986 year. Jets will be different sizes from what you have, do not order those. Here's what you can (and should) order:

  • 16155-397-971 - Float Valve ("Needle") - Quantity 2. Do not aftermarket this part. If you have to get it from a dealer, then do so. If you order from someone who is not Partzilla, but another online vendor post us a link before ordering as people like to say things like "OEM quality", "OEM style" and so on in order to fool you.
  • 93892-04016-00 - Float bowl screws. Order as many as you need for the ones that are boogered up. In the future, use a JIS #2 bit and tighten until it stops. People love to over torque these. Replacing with allens promotes over torquing as well so don't even bother unless you really must have it... but I'm asking you as a personal favour not to.
  • 93892-04012-00 - Air cut off valve cover screws. You need at least one. Order as many as you need.
  • 93892-05016-00 - CV Piston cover screws. Another one that is almost always boogered. If you need to replace them, this is the part.
  • 93892-05012-00 - Smaller bracket screws. I almost always see one ruined.
  • 93892-06014-00 - Larger bracket screws. If one is damaged (almost always assured) use a T-Handle with a JIS #3 bit in it to remove and install in the future.
  • K&L 18-2795 - Air cut off valve. You need to order two. Here is a Canadian vendor who is trusted: https://www.siriusconinc.com/products/detail/122161
  • Passage plugs - NOT NEEDED ON YOUR CARB
  • Accelerator pump - https://www.siriusconinc.com/products/detail/1094 - Please note you WILL have to trim it to fit and check everything carefully with regards to the gap.
  • K&L float bowl gaskets - https://www.siriusconinc.com/products/detail/124813 - I don't bother with other brands they all tend to swell really bad after being taken off once or twice
If you separated the carbs (and you should) you must replace the o-rings. I would do them anyways if you have not or you're unsure of their quality. Here's a spreadsheet with all the info you would need in order to assemble your own o-ring kit from a local supplier which would be of way better quality than any of the kits being sold: https://docs.google.com/spreadsheet...dT4_K5CoqDOs/edit?gid=124936446#gid=124936446
 
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If you have the money to spend I highly recommend replacing the insulators and the bands ("clamps") and the o-ring to them. They are a source of leaks on these bikes and are usually overlooked during a refresh.

https://www.partzilla.com/product/honda/16211-447-670 - Rubber insulators, you need two.
https://www.partzilla.com/product/honda/16219-ME9-000 - Insulator bands, you need two.
https://www.partzilla.com/product/honda/91325-413-830 - O-ring for the insulators, you need two. HOWEVER, I have this listed in the spreadsheet so you can probably source it cheaper locally.
https://www.partzilla.com/product/honda/95018-60250 - Air band connector (aka the air box side clamps), you need two. Really check the rubbers on that side. If they're hard and difficult to work with then heat them up with a heat gun. Not your girlfriend's hair dryer, but an actual heat gun.
 
Maraakate said:
https://www.partzilla.com/catalog/honda/motorcycle/1986/cb450sc-a-nighthawk-450/carburetor - For 1986 year. Jets will be different sizes from what you have, do not order those. Here's what you can (and should) order:

  • 16155-397-971 - Float Valve ("Needle") - Quantity 2. Do not aftermarket this part. If you have to get it from a dealer, then do so. If you order from someone who is not Partzilla, but another online vendor post us a link before ordering as people like to say things like "OEM quality", "OEM style" and so on in order to fool you.
  • 93892-04016-00 - Float bowl screws. Order as many as you need for the ones that are boogered up. In the future, use a JIS #2 bit and tighten until it stops. People love to over torque these. Replacing with allens promotes over torquing as well so don't even bother unless you really must have it... but I'm asking you as a personal favour not to.
  • 93892-04012-00 - Air cut off valve cover screws. You need at least one. Order as many as you need.
  • 93892-05016-00 - CV Piston cover screws. Another one that is almost always boogered. If you need to replace them, this is the part.
  • 93892-05012-00 - Smaller bracket screws. I almost always see one ruined.
  • 93892-06014-00 - Larger bracket screws. If one is damaged (almost always assured) use a T-Handle with a JIS #3 bit in it to remove and install in the future.
  • K&L 18-2795 - Air cut off valve. You need to order two. Here is a Canadian vendor who is trusted: https://www.siriusconinc.com/products/detail/122161
  • Passage plugs - https://www.siriusconinc.com/products/detail/2766
  • Accelerator pump - https://www.siriusconinc.com/products/detail/1094 - Please note you WILL have to trim it to fit and check everything carefully with regards to the gap.
  • K&L float bowl gaskets - https://www.siriusconinc.com/products/detail/124813 - I don't bother with other brands they all tend to swell really bad after being taken off once or twice
If you separated the carbs (and you should) you must replace the o-rings. I would do them anyways if you have not or you're unsure of their quality. Here's a spreadsheet with all the info you would need in order to assemble your own o-ring kit from a local supplier which would be of way better quality than any of the kits being sold: https://docs.google.com/spreadsheet...dT4_K5CoqDOs/edit?gid=124936446#gid=124936446
Click to expand...
Thanks for the great info! I did separate and fully disassemble the carbs, and replaced most of the o-rings. I closely followed the breakdown from LDR but didn't have all the parts to complete it. This will help though!
 
Jflava7 said:
Someone with more knowledge of carbs than I took them apart a few weeks ago and reported pinholes in the air cut valve and badly scored slides, as well as a missing slide ring seal.

I need a reliable source for obscure Keihin carburetors and parts
Click to expand...
This eeeBay seller has a very good selection of used Keihin parts which I bought from once successfully. High shipping charge, so I offered him a very low price and he accepted. And if you "watch" particular listings, he seems to automatically send lower priced offers soon after one begins "watching" the listing.
I am going to guess that the slide pistons in the VB 22G carbs (which are also original to 1982 CB450SC NightHawks) are the same slide pistons used in your CB's VB 22P carbs - @LongDistanceRider , @Maraakate , or @Flyin900 can maybe verify this.

www.ebay.com

Honda CM450-A 22G Hondamatic Carburetor Vacuum Needle Slides 1982 1983 #48 ACP15 | eBay

Parts /Bodys all threads and mating surfaces are good, brass is solid, no bad damage. Has been sonic cleaned and hand detailed pretty well, all ports/passages have been sprayed out with carb cleaner and are clear. All other removable parts have been removed. Could use a little more hand...
www.ebay.com

www.ebay.com

Honda CB400-T CM400 Carburetor Top Cover Gasket 1978 1979 VB21A # UO AP- | eBay

Find many great new & used options and get the best deals for Honda CB400-T CM400 Carburetor Top Cover Gasket 1978 1979 VB21A # UO AP- at the best online prices at eBay! Free shipping for many products!
www.ebay.com

Genuine Keihin jets will have what is called a "K-Star" symbol punched/stamped into them along with a size number like seen on these 118s :
www.ebay.com

NEW CM400 CB650 GL650 VT750 VT700 VF1100 XL600R VFR700 CBR900 CARBURETOR JET 118 | eBay

1983 GL650 A - CARBURETOR. 1984 XL600R AC - CARBURETOR. 1985 XL600R A - CARBURETOR. 1985 XL600R AC - CARBURETOR. 1986 XL600R A - CARBURETOR. 1986 XL600R AC - CARBURETOR. 1987 XL600R A - CARBURETOR. 1987 XL600R AC - CARBURETOR.
www.ebay.com
 
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Boosted said:
This eeeBay seller has a very good selection of used Keihin parts which I bought from once successfully. High shipping charge, so I offered him a very low price and he accepted. And if you "watch" particular listings, he seems to automatically send lower priced offers soon after one begins "watching" the listing.
I am going to guess that the slide pistons in the VB 22G carbs (which are also original to 1982 CB450SC NightHawks) are the same slide pistons used in your CB's VB 22P carbs - @LongDistanceRider , @Maraakate , or @Flyin900 can maybe verify this.

www.ebay.com

Honda CM450-A 22G Hondamatic Carburetor Vacuum Needle Slides 1982 1983 #48 ACP15 | eBay

Parts /Bodys all threads and mating surfaces are good, brass is solid, no bad damage. Has been sonic cleaned and hand detailed pretty well, all ports/passages have been sprayed out with carb cleaner and are clear. All other removable parts have been removed. Could use a little more hand...
www.ebay.com

www.ebay.com

Honda CB400-T CM400 Carburetor Top Cover Gasket 1978 1979 VB21A # UO AP- | eBay

Find many great new & used options and get the best deals for Honda CB400-T CM400 Carburetor Top Cover Gasket 1978 1979 VB21A # UO AP- at the best online prices at eBay! Free shipping for many products!
www.ebay.com

Genuine Keihin jets will have what is called a "K-Star" symbol punched/stamped into them along with a size number like seen on these 118s :
www.ebay.com

NEW CM400 CB650 GL650 VT750 VT700 VF1100 XL600R VFR700 CBR900 CARBURETOR JET 118 | eBay

1983 GL650 A - CARBURETOR. 1984 XL600R AC - CARBURETOR. 1985 XL600R A - CARBURETOR. 1985 XL600R AC - CARBURETOR. 1986 XL600R A - CARBURETOR. 1986 XL600R AC - CARBURETOR. 1987 XL600R A - CARBURETOR. 1987 XL600R AC - CARBURETOR.
www.ebay.com
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I saw this seller yesterday but the high shipping charges made me shy away. Nothing like $60 shipping for a $15 part
 
Yeah, but we need pictures of all the components to determine if they need replacing. Replace the float valves at a bare minimum though. Should be part of every rebuild. The jet needles, if original, don't need replacing and neither do the jets.

I've never really seen those CV pistons go bad unless someone really tried to hammer them in there or some severe corrosion from bad storage. The nylon cushions can get warped/cracked and I've seen people put them in upside and attempt to force them on and ruin them that way.
 
Jflava7 said:
I saw this seller yesterday but the high shipping charges made me shy away. Nothing like $60 shipping for a $15 part
Click to expand...
$60 ? When I input both a Winnipeg and Thompson Manitoba postal zip code into the listing for the above linked slide-pistons, it showed me only a $26 shipping charge to those areas. But, I don't know if that would become higher because of an across-the-US/Canada-border duty, tariff, or Customs import fee... I've only bought once from a Canadian-located eeeBay seller, but that occurred over a year and a half ago...
 
Boosted said:
$60 ? When I input both a Winnipeg and Thompson Manitoba postal zip code into the listing for the above linked slide-pistons, it showed me only a $26 shipping charge to those areas. But, I don't know if that would become higher because of an across-the-US/Canada-border duty, tariff, or Customs import fee... I've only bought once from a Canadian-located eeeBay seller, but that occurred over a year and a half ago...
Click to expand...
A lot changed from a year and a half ago... Not going there, but the fact remains is that shipping and fees have made things like this very cost prohibitive when buying individually.
 
Boosted said:
$60 ? When I input both a Winnipeg and Thompson Manitoba postal zip code into the listing for the above linked slide-pistons, it showed me only a $26 shipping charge to those areas. But, I don't know if that would become higher because of an across-the-US/Canada-border duty, tariff, or Customs import fee... I've only bought once from a Canadian-located eeeBay seller, but that occurred over a year and a half ago...
Click to expand...
I looked at a lot of listings last night. I remember seeing $60 but that may not have been this same seller. Either way, if I can bundle some parts into one box and save on all the individual shipping estimates, I'll definitely do that
 
Here's the pics of the worst one. Any thoughts? Does it need changing or is this normal for a 40+ year old bike?IMG_20260428_173227(1).jpgIMG_20260428_173223(1).jpg
 
Somewhere in that eeeBay cart or before u add item to the cart, you can choose from 3 shipping options…That Priority Mail Int’l one is the most expensive of the seller’s 3 offered shipping options to Canada

Edit: OR, you will find the other shipping options at Checkout and before you choose payment type and then pay
 
Last edited:
Boosted said:
Somewhere in that eeeBay cart or before u add item to the cart, you can choose from 3 shipping options…That Priority Mail Int’l one is the most expensive of the seller’s 3 offered shipping options to Canada

Edit: OR, you will find the other shipping options at Checkout and before you choose payment type and then pay
Click to expand...
Yeah, that could be. Maybe the seller displays the most expensive estimate. I'm a bit disappointed that the shipping estimate went up with the discount, from what I saw previously
 
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