1982 CM450 Carb Rebuild Kit

zhuffy

zhuffy

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I need to rebuild my carbs on my 1982 CM450C Custom and was wondering if anyone had some advice on kits. My bike is popping a bit on decel and I am told that rebuilding a dirty carb might clear this issue up. I know not to replace the brass but am I good replacing all the rubber gaskets and seals and such? How about the floats? Thanks in advance!
 
Gaskets and seals, yes. It's difficult to rebuild those VB carbs without replacing the bowl gaskets and o-rings. The floats are $$$ to get the right ones, but you only need to replace those if they've failed - most of the time they can be cleaned and reused like the jets.

I just got done with mine for the GL, essentially the same carb as yours. Use this thread for a step by step:

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

You're going to need:
Ultrasonic cleaner
can of carb spray - you'll use the whole thing.
assorted pokey objects like guitar wires, single or double strands from old control cables, etc.
a flat head screwdriver filed down to exactly fit the slots in the jets ( I want to say it's a 4MM wide blade with the tip filed to a 1MM thickness and squared off. LDR does a how-to on the one he made in the thread)
Patience
Camera phone. Take a lot of pictures of the linkage before hand.
 
Air-cutoff valve daiphragm set, (Honda) #16048-429-771
superseded to: #16048-443-901
or K&L Supply #18-2795 ?
or K&S Tech. #1003-0299 or 1003-2028

accelerator pump kit, Honda #16021-438-671
= K&L Supply 18-2808
= K&S Tech 1003-1926

Air-fuel mix pilot screw set :
K&S 56-2000

Keyster (SiriusConInc) rebuild kit : KH-1172NF

K&L float valve : 18-8955
K&L float bowl O-ring (4x) : 1003-0497
 
zhuffy said:
Also, what kinds of carbs do I have if you're able to tell by the year and bike? (as in VB22, 21, or 24): It is a 1982 CM450C Custom. Do you need a pic?
Click to expand...
The information is on the left side of the body above the float bowl mating line. Should be VB22?

Carb Information: Years, Jetting and More

There are 3 sizes of VB carbs used on the US CB/CM 400/450 engines. VB21 are 32mm venturi, VB22 are 30mm venturi and VB24 are 28mm venturi. 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...
www.vintagehondatwins.com www.vintagehondatwins.com
201_4642.JPG
 
LongDistanceRider said:
Aftermarket air cut valves are fine to use. There's tip on that in the Rebuild sticky posted earlier
Click to expand...
LDR, you seem to be the jet/needle guru. I know you have discussed this in previous discussions. I really need a source for the suggested replacement parts.

She, Mabel, is 1982 CM450E. I have rebuild the carbs using randacks $20 special rebuild kit. I know, scold me later. All brass replacement, which I now know is frowned upon. Prior to the build, it was painful to ride, spluttering shaking, barely pulled above 60 kph, backfired, front fired, (burped and farted fire as we used say with the cars) blew smoke, left side ran way hotter way quicker, was a general misery to ride. A cheap rebuild fixed 93.5% of that, leaving now just the mid range quiver. The kit I bought had different air cut off valves, so they were not changed. I cleaned the existing ones and replaced them. I get almost no backfire on downshift deceleration. The stem shafts were a mm thicker and rounded as opposed to the squared ones in the carbs.

I am dealing with, after a rebuild, bog out, gasping and shudder at mid range rpm. eg; in 5th, trying to cruise between 80 kph and 90 kph, I have to be really gentle on the throttle otherwise she will protest, after 90 though, she'll open up and keep pulling very well. It does happen periodically in 2nd, 3rd and 4th, but it is less noticeable, as most of the time i really pushing to catch up my brother's 650 before i get left behind to cruising speed at about 80 to 90.
Where can I get the ridabiltiy performance upgraded jets #61C? And to verify, that is a good step in the right direction?

I know there is a vibration from the engine at certain rpms, forcing some an early shift, which I have noted, but the quiver I refer to is fuel related as there is a stumble in the motivation. I also get a vibration from the front wheel, as it turns out is oblong not round. It's heavily weighted to counter the shake. I am looking for a wheel, which brings up another question? Is there an article, paper, video, anything related to replacing drums with disc on the front end of a CM? I figured now would be the time. After 5 day trip, loaded with camping equipment, the braking is a bit squishy.
I have many questions and will start separate threads for each.
Cheers
 
Well I'm hoping that you saved the original jets. Looking at Randakk's page I see this kit https://www.randakks.com/carburetor-kit-cb450-1983-1986-premium.html but nothing for the CM versions.
Your original jetting was a 72/115 combination, I'll recommend a 75/118 combo. Jet-R-Us sells original Keihin jets plus no name versions. Only use the Keihin jets https://www.jetsrus.com/a_jet_kit_street/honda_400_CM400_1980.html Yeah it says 400 but the jets are all the same.
I'll suggest going thru the carbs again using this thread https://vintagehondatwins.com/forums/threads/how-to-rebuild-the-vb-carburetors.24/
Float level is of concern because the only known correct float valve needles are from Honda, aftermarket ones are too long or short.
 
LongDistanceRider said:
Well I'm hoping that you saved the original jets. Looking at Randakk's page I see this kit https://www.randakks.com/carburetor-kit-cb450-1983-1986-premium.html but nothing for the CM versions.
Your original jetting was a 72/115 combination, I'll recommend a 75/118 combo. Jet-R-Us sells original Keihin jets plus no name versions. Only use the Keihin jets https://www.jetsrus.com/a_jet_kit_street/honda_400_CM400_1980.html Yeah it says 400 but the jets are all the same.
I'll suggest going thru the carbs again using this thread https://vintagehondatwins.com/forums/threads/how-to-rebuild-the-vb-carburetors.24/
Float level is of concern because the only known correct float valve needles are from Honda, aftermarket ones are too long or short.
Click to expand...
Hey LDR, I am revisiting old threats for clarity. When you recommend 75/118, is that primary/secondary respectively?
I have been confused with the naming of the jets and it needles, pins etc
.I have the 61c needles, and replaced the primary and secondary (as far as I see with 74/118. I have no power passed 2500 rpms now....
 
Yes. 75 primary and 118 secondary.
"have no power passed 2500 rpms now...." Make sure you didn't switch positions of the jets, Smaller one screws directly into the body and is closest to the mixture screw.
Is this with the airbox connected? air filter in place with lid screwed down?
 
LongDistanceRider said:
Yes. 75 primary and 118 secondary.
"have no power passed 2500 rpms now...." Make sure you didn't switch positions of the jets, Smaller one screws directly into the body and is closest to the mixture screw.
Is this with the airbox connected? air filter in place with lid screwed down?
Click to expand...
I am going to double check all that.
I was planning on removing the air box and replacing it with individual air filters (cones) how will that affect the jets/needles etc?
 
biscuits said:
I was planning on removing the air box and replacing it with individual air filters (cones) how will that affect the jets/needles etc?
Click to expand...
Some older Hondas are less bothered by it, but your bike is one of the most sensitive to complete airbox removal for pod filters and it will not run well without a LOT of jetting experimentation.
 
So she will be temperamental, like her rider...lol
Should I start with big jets or little jets?

I've seen a few cafe builds with this bike and not much detail in the carbs. I was also wondering if down the road a set of mikunis would be beneficial.
 
biscuits said:
So she will be temperamental, like her rider...lol
Should I start with big jets or little jets?

I've seen a few cafe builds with this bike and not much detail in the carbs. I was also wondering if down the road a set of mikunis would be beneficial.
Click to expand...
Mikunis might make it easier only because they're not CV carbs, but then you have more of the trial and error seat of the pants tuning to get them jetted right.

Here are a couple of threads to look at.

CM400T with pod filters needs fatter mixture.

CM400T with pod filters needs richer mixture. CM400T with pod filters needs richer mixture. What kind of main jets would be an upgrade ? Is this correct original? 1981 CM400C - 72 Primary, 118 Secondary
www.vintagehondatwins.com www.vintagehondatwins.com

'85 CB450SC Rejet/Tune w/pod filters & open exhaust

So I have been struggling getting my bike to run 'right'. I had cleaned the carbs a bunch of times. Tried working with what the PO did, they had changed the main jet to 130 (from 125 stock). Didn't run well. Added some washer/shims to the needle jet as well. That helped open throttle, and...
www.vintagehondatwins.com www.vintagehondatwins.com
 
A long time ago I found a place that would jet the mikunis according any mods in the I take/exhaust. Unfortunately I cannot, for the life of me, find that again. Still lookin though.
In the meantime I am going to remove the carbs ... again... this weekend and rejet with different sizes. It will be a loooong weekend.
Any other suggestions, clues, tips would be vastly appreciated. I have decided to go with the pods, I'm this deep already....may as well go all the way, in for a penny, in for a pound, eh?!?
 
IIRC the best jetting has been 90/125 with pods. You will need to make a ram pipe, similar to a velocity stack, that's the length of the airbox to carb boot. Entire length no just what you see.
These carbs really don't like pod filters and using them will mean some compromising in riding style and throttle use.
The company you're thinking of is Sudco which is out of business.
 
90 is big. I'd have to find some.
What would one make the ram shaft out of? Is there such thing as an aftermarket piece? Ultimately best not to fiddle with it.
 
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