SOHC.co.uk Forums > CB350/400
Carbs overflow
AndyD:
Had another play with the carbs on the bench today and tried the original valve seats / needles but these let pressure drop significantly quicker than the Keyster ones despite repeated cleaning and polishing etc.
One thing I did notice was that without the bottom bowl, the floats could occasionally stick open when turned over and then drop down with any movement. Nothing seems to be rubbing or catching and I think the spring thingy in the bottom bowl would also limit how far the floats can drop when fitted.
I plugged in the float height gauges I made up for the GS1000 a while ago to see if this could shed any light on the problem and they certainly help see what's happening.
Sure enough as soon as fuel is turned on the carbs fill and then overflow at a quick rate.
Turned the fuel off, gave the whole assembly a good shake and when turned back on the fuel level stayed at the right level.
Left them for an hour or so and no leaks.
Drained them and then turned fuel on and once again the levels go too high and overflow. And again, turning off the fuel and shaking them stops the leaking.
So it looks like for some reason the floats on initial filling don't shut off the supply but once they are 'encouraged' with a shake they work fine.
Floats and pins etc. all look fine and move very easily so I can't see any reason for this behaviour so may play a bit more on the bench before wrestling with the airbox etc. to put on the bike again.
Cheers,
Andy
Bryanj:
Slightest bid of crud or roughness on the pivot pin or iside the pivot tube can cause all sorts of troubles
AndyD:
Thanks Bryan,
I'll pop the bowls off one last time and give the pivots a final check / clean then I think I'll try them on the bike and keep fingers crossed.
Cheers,
Andy
DaveN:
Does anyone know if you can buy replacement pivot pins?
One of mine has been mangled and is shorter than the others.
Nurse Julie:
--- Quote from: DaveN on June 22, 2020, 05:39:56 PM ---Does anyone know if you can buy replacement pivot pins?
One of mine has been mangled and is shorter than the others.
--- End quote ---
Buy a length of brass rod of the correct size, model makers use it a lot, and make your own, it works out very, very cheap. On ebay, just type in brass rod. Here is the item number 133013228554
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