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CB400f - carb Air Screw query. Two screws different appearance ?

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400 Cafe Racer:

--- Quote from: Laverda Dave on September 27, 2021, 10:38:17 PM ---The black plastic caps were fitted over the screws to limit the amount of adjustment by the owner as K2-K6 suggested. If you find all these still in place on a 400/4 consider yourself very lucky as they were frequently removed during a carb adjustment and lost (trying to put them back onto the brass screws on carbs 2&3 requires fingers six inches long and as thin as a matchstick)!
They are like gold dust to find s/h, you might find the odd one but never four together!
On a personal note, when I rebuild the carbs on a 400/4 (seems to be a frequent thing I have to do!) I adjust the air screw to two turns out and then replace the plastic caps with the stops at the six o'clock position. This will allow the air screw to be adjusted 1/2 turn either way.

--- End quote ---

Hi Dave and K-K6,

Thanks very much for your confirmation, this is how it appeared to me on close up examination of the photo. I appreciate the tip about how to remove and replace the caps.

At the moment Cyl 1 seems too rich on idle and will not respond to the capped adjustment. It is so rich it prevents combustion. I have set float levels and there is no visible flooding or petrol from the drain tubes. I am working on the assumption that if these are capped they may well have never been removed, so I will remove them all, soak well down the tubes and airways with cleaner, and then give them a good blow through withh compressed air. The pilot jets seem clear.

Cheers :)

Dennis

wildtapholer:

--- Quote from: 400 Cafe Racer on September 27, 2021, 09:37:07 PM ---Hi Guys,

Just getting down to adjusting the carbs after the engine, strip, inspection, rebuild.  I have noticed that 3 carbs, 1,3 and 4 have a black largish air screw that will only rotate 270 degrees before it meets a "stop" on the carb casting. (Picture 1)

Carb 2 has a smaller diameter screw with a spring which looks like a conventional type that will screw all the way in or out over several turns.
(Picture 2)

Have you come across this ?

--- End quote ---
I was lucky, my carbs had the plastic cover on all my air screws and I asked what they were on the American site before joining this one, just a cover really with a stopper as to not go more than one turn when in place, he actually asked if I would sell them. When I stripped my carbs down I turned the screws all the way in then out 2 turns then placed the caps back on so can turn out one full turn before hitting stopper making 3 turns out if needed being as my manual says 2 turns out.

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