There are 3 sizes of VB carbs used on the CB/CM 400/450 engines.
VB21 are 32mm venturi, VB22 are 30mm venturi and VB24 are 28mm venturi.
Black floats which are adjustable are found on 1978 and ’79 carbs.
In 1980 the floats changed to white, although they rarely look white, and a different float needle. The white floats are non-adjustable[attachment=7:1bformrk]late float needle.jpg[/attachment:1bformrk][attachment=8:1bformrk]early float needle.jpg[/attachment:1bformrk] The black floats can be used in place of the white ones by changing the float needle.
1980 also started using accelerator pumps on all carbs.
1983 saw the change to a single main jet.
VB21 carbs are found on 1978/79 CB/CM 400 manual transmission bikes.
1978 T 1&2 use VB21A with a #75 primary main jet and a #105 or #110 secondary main jet.
1979 CB400T 1&2 use VB21B with #75/105 jetting. Both years use the same needle.
1979 CM400T uses VB21C with #70/112 and a different needle...
Mixture screw starts at 1 ½ turns out.
Slow jet is not documented but I suspect it’s#38.
Throttle plates measure at 1.448"
VB22 2 jet carbs are found on 1980 thru 1982 CB/CM 400/450 manual trans engines.
1980/81 CM400T & C use VB22A with 72/118 jetting.
1980/81 CB400T uses VB22B with 70/110 jetting.
1980/81 CM400E uses VB22E with 72/118 jetting.
1982 CB450T uses VB22L with 70/108 jetting.
1982 CM450C and CB450SC use VB22G with 72/115 jetting.
1982 CM450E uses VB22J with 72/115 jetting.
All of the 2 jet VB22 carbs use the same needle from 1980 thru 1982.
These all seem to use a #38 slow jet.
Throttle plates measure at 1.365"
Single Main Jet VB22 carbs started in 1983 thru the end in 1986
1983 CB450SC uses VB22N with a 120 main, #38 slow jet.
1983 CM450E uses an unknown number VB with a 120 main, #38 slow jet.
There are no 1984’s according to Honda but they do exist, no info on them.
1985 Federal(49 state) CB450SC uses VB22EA with a 125 main, #38 slow jet.
1985 CA only CB450SC uses a VB2FA with a 125 main, #38 slow jet.
1986 CB450SC uses a VB2FB with a 125 main, #38 or #40 slow jet.
There are 2 different needles in 1983 for both versions. 1985 uses the later of those 2 on both version. 1986 uses 2 different needles one from the 85 carbs and a different number one.
VB24 carbs are found on Automatic transmission models only
1978 CB400A uses VB24A with #72/105 jetting Note post#97: slow/idle jet #42
1979 CM400A uses VB24B with #65/110 jetting with a different needle.
1980 uses VB24C with #68/112 jetting.
1981 uses VB24C with 68/112 jetting. 1982 uses VB24E with 75/108 jetting and a #35 slow jet.
1983 is a single main jet #120 with a #38 slow jet and a different needle.
1980/81 are the only years using the same needle.
VB31 carbs for non USA models
VB31 F carbs (32mm venturi), jets, primary #72, secondary #110, idle #35
Float levels for all of the carbs and variations are 15.5mm +/-.5mm. A higher float level, lower measurement number, enriches the carb thru out its range while a lower level, higher measurement number, leans the carb.
Initial Mixture settings range from 1.5 to 2.5 turns out. These are purely an initial setting to get the engine running. The mixture on each carb has to be tuned after the engine is hot and the bike ridden for @10 minutes.
High altitude adjustments (over 6500 ft.)
1979 CM400T #108 secondary main jet, ½ turn in on mixture screw
1979 CM400A ½ turn in on mixture screw, no jet change
1980 CB400T #105 secondary main jet, ½ turn in on mixture screw
1980 CM400E #112 secondary main jet, ½ turn in on mixture screw
1982 and later ALL Models ½ turn in on mixture screw
Bulletins:
1982 CM450A Drivability Performance Improvement
“Under part-throttle at low speeds some CM450 Automatic owners may experience poor drivability. This condition can be improved by installing a vacuum cylinder Spring Collar kit and wider gapped spark plugs specified for 1983 450’s “.
Part number 16020-MC1-305 Spring Collar Kit. This is that white plastic ring on top of the carb body when you remove the piston.
Spark plugs specified are NGK DPR8EA-9 gapped at .032”-.036”
1982 CB/CM 450 Drivability Performance Improvement (all manual transmission models: CB450SC, CB450T, CM450C and CM450E
“ Under part throttle operation, some owners of these motorcycles may experience poor drivability performance. This condition can be improved by fitting replacement jet needles”
First step is to replace the needles #61A with new needles #61C. Second step is to replace the mixture screws.
Part numbers: 16113-MC0-305 Needle Jet #61C and 16016-413-751 Pilot Screw
The needle is a the standard needle for a 1983 CM450 A and the Pilot/mixture screw changes numbers to 16016-KC2-970 and shows available still on 4-23-2013. The screw has been used on 121 different engines from 1980 to 2004.
New Info: viewtopic.php?f=59&t=22607&p=176386#p176386
Carb Insulators/Boots
The boots for CB/CM 400 manual transmissions seem to be available thru Honda sporadically. 16211-447-000
The insulators for the 450 engines do fit and work without modification 16211-447-670 . The o-rings to seal them are always needed 91325-413-830 .
I would suggest using a Dremel with a sanding drum to smooth the transistion from the carb to the boot as well as the transistion from the boot to the head for better flow.[attachment=9:1bformrk]201_4550.JPG[/attachment:1bformrk] The insulators for the 400A aren't available and it seems the ones for the manual transmission are too large.
Emission Controls
In 1985 a "evaporative emmisons control system" was added.[attachment=1:1bformrk]201_4577.JPG[/attachment:1bformrk][attachment=0:1bformrk]201_4576.JPG[/attachment:1bformrk]
Spark Plugs
Since they are critical to how the carbs work I've included them
1978 thru 81 use either NGK D8EA or Nippon Denso ND X24ES-U gapped at .024-.028"
For cold weather running, under 41*F D7EA or X22ES-U, same gap
For extended or high speed running D9EA or X27ES-U
Always the same gap
1982 is a different plug. NGK DR8ES-L or ND X24ESR-U gapped at .024-.028"
Cold weather is DR7ES-L or ND X22ESR-U
High speed is DR9ES-L or ND X27ESR-U
1983 is another plug change and new gap. NGK DPR8EA-9 or ND X24EPR-U9 gapped at .032-.036"
Cold weather is DPR7EA-9 or X22EPR-U9
High speed is DPR9EA-9 or X27EPR-U9
This plug runs thru 1986
Canadian 400's use DR8ES-L gapped at .024-.028"
Here's a chart for plug readings[attachment=6:1bformrk]spark-plug-condition-colour-640x266.jpg[/attachment:1bformrk]
This is the best information I have been able to retrieve to date. Errors? Let me know. More info, let me know and I'll add it.[attachment=5:1bformrk]201_4577-001.JPG[/attachment:1bformrk][attachment=4:1bformrk]201_4577-002.JPG[/attachment:1bformrk][attachment=3:1bformrk]201_4577-003.JPG[/attachment:1bformrk][attachment=2:1bformrk]201_4577-004.JPG[/attachment:1bformrk]
VB21 are 32mm venturi, VB22 are 30mm venturi and VB24 are 28mm venturi.
Black floats which are adjustable are found on 1978 and ’79 carbs.
In 1980 the floats changed to white, although they rarely look white, and a different float needle. The white floats are non-adjustable[attachment=7:1bformrk]late float needle.jpg[/attachment:1bformrk][attachment=8:1bformrk]early float needle.jpg[/attachment:1bformrk] The black floats can be used in place of the white ones by changing the float needle.
1980 also started using accelerator pumps on all carbs.
1983 saw the change to a single main jet.
VB21 carbs are found on 1978/79 CB/CM 400 manual transmission bikes.
1978 T 1&2 use VB21A with a #75 primary main jet and a #105 or #110 secondary main jet.
1979 CB400T 1&2 use VB21B with #75/105 jetting. Both years use the same needle.
1979 CM400T uses VB21C with #70/112 and a different needle...
Mixture screw starts at 1 ½ turns out.
Slow jet is not documented but I suspect it’s#38.
Throttle plates measure at 1.448"
VB22 2 jet carbs are found on 1980 thru 1982 CB/CM 400/450 manual trans engines.
1980/81 CM400T & C use VB22A with 72/118 jetting.
1980/81 CB400T uses VB22B with 70/110 jetting.
1980/81 CM400E uses VB22E with 72/118 jetting.
1982 CB450T uses VB22L with 70/108 jetting.
1982 CM450C and CB450SC use VB22G with 72/115 jetting.
1982 CM450E uses VB22J with 72/115 jetting.
All of the 2 jet VB22 carbs use the same needle from 1980 thru 1982.
These all seem to use a #38 slow jet.
Throttle plates measure at 1.365"
Single Main Jet VB22 carbs started in 1983 thru the end in 1986
1983 CB450SC uses VB22N with a 120 main, #38 slow jet.
1983 CM450E uses an unknown number VB with a 120 main, #38 slow jet.
There are no 1984’s according to Honda but they do exist, no info on them.
1985 Federal(49 state) CB450SC uses VB22EA with a 125 main, #38 slow jet.
1985 CA only CB450SC uses a VB2FA with a 125 main, #38 slow jet.
1986 CB450SC uses a VB2FB with a 125 main, #38 or #40 slow jet.
There are 2 different needles in 1983 for both versions. 1985 uses the later of those 2 on both version. 1986 uses 2 different needles one from the 85 carbs and a different number one.
VB24 carbs are found on Automatic transmission models only
1978 CB400A uses VB24A with #72/105 jetting Note post#97: slow/idle jet #42
1979 CM400A uses VB24B with #65/110 jetting with a different needle.
1980 uses VB24C with #68/112 jetting.
1981 uses VB24C with 68/112 jetting. 1982 uses VB24E with 75/108 jetting and a #35 slow jet.
1983 is a single main jet #120 with a #38 slow jet and a different needle.
1980/81 are the only years using the same needle.
VB31 carbs for non USA models
VB31 F carbs (32mm venturi), jets, primary #72, secondary #110, idle #35
Float levels for all of the carbs and variations are 15.5mm +/-.5mm. A higher float level, lower measurement number, enriches the carb thru out its range while a lower level, higher measurement number, leans the carb.
Initial Mixture settings range from 1.5 to 2.5 turns out. These are purely an initial setting to get the engine running. The mixture on each carb has to be tuned after the engine is hot and the bike ridden for @10 minutes.
High altitude adjustments (over 6500 ft.)
1979 CM400T #108 secondary main jet, ½ turn in on mixture screw
1979 CM400A ½ turn in on mixture screw, no jet change
1980 CB400T #105 secondary main jet, ½ turn in on mixture screw
1980 CM400E #112 secondary main jet, ½ turn in on mixture screw
1982 and later ALL Models ½ turn in on mixture screw
Bulletins:
1982 CM450A Drivability Performance Improvement
“Under part-throttle at low speeds some CM450 Automatic owners may experience poor drivability. This condition can be improved by installing a vacuum cylinder Spring Collar kit and wider gapped spark plugs specified for 1983 450’s “.
Part number 16020-MC1-305 Spring Collar Kit. This is that white plastic ring on top of the carb body when you remove the piston.
Spark plugs specified are NGK DPR8EA-9 gapped at .032”-.036”
1982 CB/CM 450 Drivability Performance Improvement (all manual transmission models: CB450SC, CB450T, CM450C and CM450E
“ Under part throttle operation, some owners of these motorcycles may experience poor drivability performance. This condition can be improved by fitting replacement jet needles”
First step is to replace the needles #61A with new needles #61C. Second step is to replace the mixture screws.
Part numbers: 16113-MC0-305 Needle Jet #61C and 16016-413-751 Pilot Screw
The needle is a the standard needle for a 1983 CM450 A and the Pilot/mixture screw changes numbers to 16016-KC2-970 and shows available still on 4-23-2013. The screw has been used on 121 different engines from 1980 to 2004.
New Info: viewtopic.php?f=59&t=22607&p=176386#p176386
Carb Insulators/Boots
The boots for CB/CM 400 manual transmissions seem to be available thru Honda sporadically. 16211-447-000
The insulators for the 450 engines do fit and work without modification 16211-447-670 . The o-rings to seal them are always needed 91325-413-830 .
I would suggest using a Dremel with a sanding drum to smooth the transistion from the carb to the boot as well as the transistion from the boot to the head for better flow.[attachment=9:1bformrk]201_4550.JPG[/attachment:1bformrk] The insulators for the 400A aren't available and it seems the ones for the manual transmission are too large.
Emission Controls
In 1985 a "evaporative emmisons control system" was added.[attachment=1:1bformrk]201_4577.JPG[/attachment:1bformrk][attachment=0:1bformrk]201_4576.JPG[/attachment:1bformrk]
Spark Plugs
Since they are critical to how the carbs work I've included them
1978 thru 81 use either NGK D8EA or Nippon Denso ND X24ES-U gapped at .024-.028"
For cold weather running, under 41*F D7EA or X22ES-U, same gap
For extended or high speed running D9EA or X27ES-U
Always the same gap
1982 is a different plug. NGK DR8ES-L or ND X24ESR-U gapped at .024-.028"
Cold weather is DR7ES-L or ND X22ESR-U
High speed is DR9ES-L or ND X27ESR-U
1983 is another plug change and new gap. NGK DPR8EA-9 or ND X24EPR-U9 gapped at .032-.036"
Cold weather is DPR7EA-9 or X22EPR-U9
High speed is DPR9EA-9 or X27EPR-U9
This plug runs thru 1986
Canadian 400's use DR8ES-L gapped at .024-.028"
Here's a chart for plug readings[attachment=6:1bformrk]spark-plug-condition-colour-640x266.jpg[/attachment:1bformrk]
This is the best information I have been able to retrieve to date. Errors? Let me know. More info, let me know and I'll add it.[attachment=5:1bformrk]201_4577-001.JPG[/attachment:1bformrk][attachment=4:1bformrk]201_4577-002.JPG[/attachment:1bformrk][attachment=3:1bformrk]201_4577-003.JPG[/attachment:1bformrk][attachment=2:1bformrk]201_4577-004.JPG[/attachment:1bformrk]
mine is vb31 too
