SOHC.co.uk Forums > CB500/550

New needles don't fit!

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Sesman:
I was caught out by this very same issue. I bought a set of refurbished carbs from overseas intending to replace my existing 069a variants, but in the end decided to rebuild my own set to maintain the bikes originality. It was only after I sold them on to another member I later discovered they were the ones for Germany/France export.

I have absolutely no idea what the technical implications are will be using o22a carbs on a UK/USA model , but I wager Oddjob will.

bbrian66:
Ok here's a little update. I've found a set of 069a carbs which are of another bike i own but are in a terrible state. I've stripped them down today. The needle is stamped 273004 which seems correct for an 069a carb, according to the book.this needle is faster than the 272304 needle that's in the 022a carb and will not fit into the throttle valve from the 022a.
To my OP, the new needle in the refurb kit still doesn't fit in the throttle valve of the 069a carb so i guess that's an issue I need to take up with the vendor of the kit.
Today's thought: the bare carb bodies of the 022a and 069a look identical. The only identifying marks are casting inside the float chamber that says A-2. This is present in both carbs. The 069a carbs are in a terrible condition,  with lots of corrosion inside the passageways.  The 022a carb bodies are immaculate. The choke levers in the 069a carbs are seriously rusty whereas the 022a choke levers are in really good condition.
So - can i build all the necessary 069a parts into my 022a carb bodies,  using the 022a choke levers and shafts but the 069 throttle valves  along with a decent set of new 069a jets, needles, etc.

bbrian66:
Edit: both needles are the same o/a diameter, which makes more sense! Don't know where i got that from

Oddjob:
There appear to be some differences between the 022a and the 069a carbs.

First off the jets are different, 100/40 in the 022a and 98/38 in the 069a.

As you've found out the needles are different, 272304 in the 022a and 273004 in the 069a. The emulsion tube changed as well, more holes in the 069a ones so more air v fuel, in line with the drive to make the bike more emission friendly back in the day. The clip position changed as well from 4th to 2nd.

The airscrews went from hollow tipped in the 022a to solid tipped in the 069a.

In total the 022a was not designed to suit the 550F, it's meant for a 4 into 4 exhaust system. Will it work, yes, after a fashion.

The question of swapping all the internals from the 069a carbs into the 022a bodies is a good one. As long as you swap everything, including the slides holding the needles I'd say it will work. The bodies are almost identical with no extra drillings I can recall.

So go for it. Let us know if it improves anything. Chokes are the same on both bodies so you can swap those as well.

bbrian66:
Great stuff - thanks Oddjob!
I'll do just that. It will be a good while before I'll know any results as I'm still waiting to assemble the engine.

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