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Discussion Starter · #1 ·
This is probably a really really dumb question... AND would be fairly obvious if I had a 450 here to look at, but since I dont Ill ask here and suffer the humiliation LOL :?

Are the carbs the same on a 450 as a 500T?
I know the jets could be different sizes (but not necessarily from what Ive seen) and there is that blasted air cutoff valve, but, are they physically the same carbs otherwise? Would they work and mount up OK?

I guess my ?? is this..would it be a simple swap out to put 450 carbs on a 500T? What probs would I likely encounter other than possibly rejetting?

Bring on the "Are you nuts" stuff :lol: :lol: :lol: It's justa thought I think Im thinking since repair parts for these 500 carbs are impossible to find... :? :D



NOTE: what Im really needing are 2 bowl gaskets and the orings for the air cut off valve (can prolly match some up at the hardware store that will work on these if need be). If anyone would have them and willing to part with them let me know.Please ;)
 

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Looking at the parts numbers, a lot of stuff in a 500 carb actually has 283 and 292 part numbers (450 numbers).
The manifold rubber things ("carb insulators") are a 500 part number (375), not sure why - the gasket between it and the head is a 450 number.
Throttle cable is a 500 number, again not sure why, maybe because it's black.
As far as I know, all the 500 cables are the same as 450, just black.........

Jet sizing is pretty equivalent - I think 500's had 140-150 mains, slow jets were 35-40 maybe???
Same part numbers on 500 jets as 450.

So I'd say there's a high probability of success on your idea.
Certainly something I'd think about if I had a 500T.
 

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Discussion Starter · #3 ·
tbpmusic said:
Looking at the parts numbers, a lot of stuff in a 500 carb actually has 283 and 292 part numbers (450 numbers).
The manifold rubber things ("carb insulators") are a 500 part number (375), not sure why - the gasket between it and the head is a 450 number.
Throttle cable is a 500 number, again not sure why, maybe because it's black.
As far as I know, all the 500 cables are the same as 450, just black.........

Jet sizing is pretty equivalent - I think 500's had 140-150 mains, slow jets were 35-40 maybe???
Same part numbers on 500 jets as 450.

So I'd say there's a high probability of success on your idea.
Certainly something I'd think about if I had a 500T.
Just the guy I had in mind to respond to this! THANKS BILL! :cool: I figured if anyone would know it might be you bud. :cool:

Thats kinda what I was looking at as well ..there are a lot of interchangable parts in those carbs.
I also have no idea why the insulators are a different number... but I cant see where/why they would be any different.Hmmm...Possible a slightly different angle/length is all I can think of ..and if thats all it is I can simply reuse the 500 rubbers and put them on the 450 carbs.

The throttle cable on mine is broken also, and it IS impossible to find.

Are the 450's Gray instead of Black like the 500? :lol:
And does the cable split into 2 cables about halfway down? Going to each carb?
Orrr...Does the 450 use 2 cables on it coming out of the handlebar control.1 Push/1 Pull cables? THAT may well be the difference if so.

If so I may have to just replace the cables and handlebar control to the 450 ones and Ill be good to go.

YUP! The jet sizes are pretty much the same from what I see too..the 450 uses #145-150 mains. The 500 uses #140-150 mains
450 pilots are 38's? The 500 uses 35's-40's
450 slows are 38's as well? The 500 uses 35-40's as well, sooo...again same.

:eek: WOW!Im thinking this just might be the way to go here, bud! :cool: :cool:
 

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I'm pretty sure the throttle cables are the same, just different colors.
All 450 cables were gray, a single cable from the grip splitting under the tank.
Same "throw" and everything, I think.
Black ones are around - when I redid my 450 I used black cables. The Tach cables are pretty scarce, but not the others.

A large number of 450's used 130 or 135 mains - depends on the K-series.

There are actually only two jets in a 450 carb, the main and the slow. Another which appears to be a jet is actually a solid plug, over the slow jet area. That's what the pencil is indicating.
It's brass, screws in, looks like a jet, might even have a number on it - but there ain't no hole in it.
The real slow jet is down that hole that's being plugged - that jet is a long, slender affair, takes a little bitty screwdriver.
All the fuel to the slow jet goes through a cross-drilled channel.



Remove that plug, you'll see this -

#1 is where the plug was removed, down in there will be the slow jet - #2 is the area where you can see the cross-drill to the main jet area, #3 is a round brass ball they use to seal the cross-drill after it's made (you can also see it in the first photo).
So fuel goes through the main jet, through the cross-drilled channel (with the plug in place), then through the slow jet.



The only real question is WHY would they want to change something so simple and effective??
Never figured it out.
 

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Discussion Starter · #5 ·
Only 2 jets? WOW! I see it sure does. :shock: :shock: Thanks for the photos Bill :)
I was going on the fiche from Western Hills Honda for a '74 450 K7 for the jet sizes etc. Thats what they have listed.Weird! :shock:

Man...THAT really is a simple and effective design, and I too have to question ...WHY mess with it??

Im pretty sure i know what that slow jet looks like you're talking about and yup , one of those nice lil pocket screwdrivers NAPA used to giveaway works really nice on getting those out. ;)

Thanks for the tip on the cables as well. After searching everywhere to no avail for a correct 500 cable I ended up getting a universal inner cable for $2 bucks and change from Dennis Kirk. It already has the upper handle clip on it, its exactly the same size cable as well and all ill have to do is hook the carbs up and cut the cable to length and crimp a lil lead fishing weight on it to hold it then and it should work just fine now. Cheap but good fix for a broken cable with a good outer housing. ;)

Ill try these 500 carbs out now that ive cleaned em and see how they do. BUT if theyre not right Im swapping to 450 carbs! ;)


Thanks a million Bud!! :cool: :cool: You ARE the man!
 

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trublu said:
Only 2 jets? WOW! I see it sure does. :shock: :shock: Thanks for the photos Bill :)
I was going on the fiche from Western Hills Honda for a '74 450 K7 for the jet sizes etc. Thats what they have listed.Weird! :shock:
Thanks a million Bud!! :cool: :cool: You ARE the man!
No, the fiche is right - last few years of 450's did use 140-150 mains.
Mine is a K4, and I run 130's right now.......my K2's also ran 130's..............
 

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If you're gonna go crimping something on the end of that cable then I highly recommend slightly fraying the cable underneath of the crimped on "barrel" and then applying flux/solder to the cable to prevent it from ripping loose..

GB :mrgreen:
 

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Discussion Starter · #9 ·
Yeah gonna put a lil solder ball on the tip to stop that . ;) Theres really plenty of room in the (cable splitter housing?) for it.

GB, I sure dont think its what was originally used BUT the little ball thingy on the splitter end of the upper cable looks and feels like a regular ol lead split fishing weight crimped on there. :eek:

Hey, its wortha shot guys. The worse that could happen is that it just comes off somehow and I'll have no throttle.

Eh, And..If it dont work. I'll just pony up and buy a new fo fitty cable (THANKS Bill!) :cool:
 

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Discussion Starter · #10 ·
tbpmusic said:
trublu said:
Only 2 jets? WOW! I see it sure does. :shock: :shock: Thanks for the photos Bill :)
I was going on the fiche from Western Hills Honda for a '74 450 K7 for the jet sizes etc. Thats what they have listed.Weird! :shock:
Thanks a million Bud!! :cool: :cool: You ARE the man!
No, the fiche is right - last few years of 450's did use 140-150 mains.
Mine is a K4, and I run 130's right now.......my K2's also ran 130's..............
Ahhh..Ok now that makes sense. ;) My 500 is a '75 and I just went back to the closest year 450 for the illustration is how I got the K7 one to go by.
 

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Discussion Starter · #12 ·
:shock: Thats a GREAT site!! :cool:
THANKS GB!! ;) :cool:
 

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No problem man.. I ordered all of my parts for my cables from them when I built them for my Mikunis. They shipped em out really fast and everything was perfect. Worked like a charm while testing/jetting but I have yet to re-assemble and put any miles on anything..

Flanders has a little (or a lot) of everything.. Plus they've been around and in business forever.... ;)

GB :mrgreen:
 

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You can get thin gasket paper and make the bowl gaskets. Making gaskets when you need 'em simplifies one's life - and saves money. And gets you gaskets when you need them.
 

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Discussion Starter · #15 ·
GB, They sure do have a little of everything . Perfect!WOW! THAT site is definitely a "favorites" saver guys! Thanks again bud. :cool:

Kerry, Im not to worried about the bowl gaskets. Like you said I can make those. I really need the air cut off orings. Ill have to see what I can come up with locally. Im about ready to just block off the dang things really. :twisted:
 

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Figure I'd ask my question here rather than start a new thread.

500t carbs on my cb450?

The guy who owns a local shop (http://www.charlies-place.com/) that works only on late 60's - late 70's Hondas recommended this as an upgrade. He said the 500t carbs bolt right up with the 450 but have a different diaphragm and I think he said "accelerator pump" that make them more efficient and improve throttle response. Judging by his website alone he seems like a guy I might listen to.

Any thoughts?
 

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brokenglass said:
Figure I'd ask my question here rather than start a new thread.

500t carbs on my cb450?

The guy who owns a local shop (http://www.charlies-place.com/) that works only on late 60's - late 70's Hondas recommended this as an upgrade. He said the 500t carbs bolt right up with the 450 but have a different diaphragm and I think he said "accelerator pump" that make them more efficient and improve throttle response. Judging by his website alone he seems like a guy I might listen to.

Any thoughts?
There is no "diaphragm" on either the 450 or 500T carbs.
There is also no "accelerator" pump on either type, just an anti-backfire device on the 500T carb, Honda calls it a "cutoff valve", not present on the 450 type. This device does have a small diaphragm of sorts - mainly it's a pain in the butt.

Otherwise they're about the same, except for jetting (typically, depending on your "K" model).
Personally I'd stay with the 450 carbs, I wouldn't consider it an upgrade at all. You can't get any more simple than a 450 carb, and simple usually equals good.

But you can do what you like, of course, listen to whomever you wish - it's your bike.
 
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