‘Spare’…. hmmmm… o ring

Windmill John

Windmill John

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Joined
Jun 4, 2022
Total Posts
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Location
East Sussex, England
Just rebuilt carb and….. argghhh!!! Where’s this bugger from!?

I removed again the accelerator pump, not that one. I removed again the two air cut off diaphragms, not the seal from either of those.

Any ideas? Cheers.
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IMG_0336.jpeg
 
Actually.. I do recall an o ring sitting in situ when I removed the accelerator pump weeks ago, but I cannot see a position for it now and I cannot see it in the exploded diagram in Clymer!
whilst I’d rather resolve this before sticking them back on the bike, I may try without….. and wait for a:
Fuel leak!
Air leak,
Nothing to happen… perfect 😊
 
Feel for your situation. Just went through the opposite on my cb160. CMSNL diagrams depict an air screw o-ring that was on neither of the existing air screws nor in the 'complete' rebuild kit from Common. Having said this... it's running great now and looks like it doesn't require one? Fun with vintage bikes! Best of luck.
 
Ahaa… checked David Silver and it probably is the mixture screw.
Clymer picture wrong. When I removed the mixture screws, I only recall the tiny metal washers.
See… I’ve answered my own question; possibly. 😉
 
Just saw your post. Yes mine didn’t have one in either mixture screw. I’ll pull them out and see how I feel. If Clymer was correct, then the spring and screwing them in would tear the o rings. So I guess it’ll be o ring, metal washer then spring.
 
Well, don’t tell me off, but having separated this type of linkage before and then had a leak at the crossover, I didn’t actually separate the carbs, so not that.
I did though, fully flush the crossovers.
 
if it ain’t broke, no sense in fixing it!

Is it possibly part of the old “boot” on the accelerator pump that tore off?
 
Not part of the boot. There’s definitely an indent all the way round the o ring where it’s been pressed against something.
No worries, when the novelty of searching wears off, I’ll refit the carbs and test.
Appreciate the input though.
 
Do you have this O ring in the accelerator pump bowl, since you have a leak in the drain pipe on this bowl? This picture is missing the O ring too, yet there is a round one that needs to be in there. It will leak like a #$%## if you don't have one in place. :(

P1090658.JPG
 
The O ring was there.
When I compared the ‘spare’ o ring size with the mixture screws, I decided to fit new o rings there, even though it’s not clear it has them.
They‘ll have a tiny effect on mixture, but I can tweak when running.
Thanks for all input, carbs can go back on the bike the next time I’m in the shed.
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Wrong order. From carb body out:

O-ring
Washer
Spring
Screw

Ring seals to limit air from entering around the mixture circuit.
 
I was just testing you…. 😉 The way I have it, wouldn’t that also stop fuel or air entering via the threads?
Also, if o ring goes in first, that would be a pain to remove. Maybe the spare o ring was blown out from there…
 
Windmill John said:
I was just testing you…. 😉 The way I have it, wouldn’t that also stop fuel or air entering via the threads?
Also, if o ring goes in first, that would be a pain to remove. Maybe the spare o ring was blown out from there…
Click to expand...
The O-ring seats against the carb body, the washer squishes the O-ring to seal on the screw. The way you have it the threads will just cut into the O-ring ruining it.
 
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