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Looking for a little help. I've been asked to fix up a CB450 K0 and make it reliable. I've done a complete rewire, and rebuilt the carbs. Trying to get it running 100% before I fit a Pamco ignition.

I'm used to working on electrics but never worked on carbs before. I cleaned them out and replaced the needle, jets, valve, floats and seals. Checked the sliders and they're free and slide up and down nicely. There were some springs on them to push them down which I removed as I didn't see them on any parts diagram. Bench set and throttle synced according to common-moto youtube video.

Started it up and it runs nice but the idle is high (4000). Butterfly stop was set with a guitar string and the idle screw was set by fully screwing in and backing off 1 1/2 turns.

Looking for some advice where to start. The butterfly is definitely a little open because it was set with a guitar sting my instinct is to back this off and shut the throttle completely just wanted some advice first. What is the effect of the butterfly stopper and what is the effect of the idle mixture screw? How do I adjust each one.

Also there is a little leak around the float bowl gasket. I can't really put and pressure on it how do I fix this? Gasket maker?
 

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I am fairly certain those springs in the slides are needed.
 

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The guitar string/drill bit/ whatever is to bench sync the carbs. For idle adjustment the butterflies will be very nearly completely closed.

I don't see any springs on the parts fiche for the K-0 either, possibly someone has swapped in a newer set of carbs. In any case there are bonafide experts on the 450s around here who will be able to help you get it on the road.
 

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I don't believe there were ever any springs in the 450's CV carbs - the weight of the aluminum piston does it for them, as opposed to the most-likely lighter slide with diaphragm on the 350's CV carbs. Possibly someone had an issue with it returning to idle in the past and took that route to "fix" it
 

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K0 bikes had issues early some of them got retrofitted with springs in the carbs. Can't remember exactly why but they did get them. Bill will surely chime in with the reason if he sees this.

We used to have some of the recall paperwork here on the for them, one of then was for that. If I remember in the morning I will dig through my files and see if I have them stlll.

Sent from my SAMSUNG-SM-G891A using Tapatalk
 

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So I tried it again this morning and partially closed the choke and was able to get it to idle nicely around 1200rpm. So my first step is to back off the air screw or stop screw.

Do I need to adjust the idle mixture screw after this?

Also as it air-cooled is then much risk of it over heating? The oil is 1000miles or 3 years old so I'm going to change that in advance of fitting the electronic ignition .
 

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As long as the bike is moving and gets some air flow, it won't overheat - but you can't let it sit still and idle for too long.
 

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did you put genuine Honda jets in the carbs? If not, do so because many aftermarket kits do not contain the proper sized jets thus causing all sorts of issues.
lastly, not talking junk but a lot of our members have had ongoing reliability issues with PAMCO. do a search here for good measure before you proceed. Doesn't hurt to gather info and draw your own conclusion.
 

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So I tried it again this morning and partially closed the choke and was able to get it to idle nicely around 1200rpm. So my first step is to back off the air screw or stop screw.
You need to sync the carbs, they need to be working in unison before you start screwing things in and out. set the idle stop screws so that your idle is around 1k, 1.2k is fine too, you can do this with the throttle cables disconnected to eliminate them hanging up the stop screw. once you have the bike idling nicely with both carbs identical, don't touch. Your choke should NEVER need to be on during normal operation, only during start-up if at all.

Do I need to adjust the idle mixture screw after this
yes, you need to adjust to get proper mixture. follow instructions in your FSM. Turn in to lean, and out to enrich. Check your plugs goldilocks style, white is too lean (hot) black is too rich (cold/too much fuel) golden brown, tan, honey glazed, crispy croissant color are good. There are probably around 50+ posts that outline the procedure for this, many by members more qualified to give advice than I am. Do a thorough search if you are still encountering problems.

***MAKE ALL FINAL ADJUSTMENTS AT OPERATING TEMP***


Also as it air-cooled is then much risk of it over heating? The oil is 1000miles or 3 years old so I'm going to change that in advance of fitting the electronic ignition .
hope this helps
 
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