Quick carburettor question

Mick Rae

Active Member
Background: I posted here in the summer about HIF6 cab overflowing. At the time, I took the float bowl components to bits, cleaned, reassembled. It was fine for 100miles, then overflowed again (pulsing out). Repeated, reset float height, replaced filter. Fine for 450miles, did it again.
Action to be taken: I noted at the time the spindle for the float looked very worn. So I have purchased new spindle, new float, new valve/seat.
The question: my old needle valve had no spring button where to contacts the float, but new valve does. Is there anything specific I need to do different when using this now valve with a spring? My plan it to take the old bits out, clean the bowl, install new parts. Then set the middle bit of the float to 1mm (approx!) below the edge of the bowl. Is this still the procedure even with spring needle? How accurate is the 1mm measurement needed to be (hard to measure completely accurate with things moving so easily is my thought!).
Thanks in advance for your time and advice, it is always very much appreciated.
Mick
 
I think you will find that the weight of the float will not compress the needle valve spring at all, but the rising fuel will be shut off when the float touches the spring button. Therefore I would set as before as when using an un sprung needle.

Constant flooding points to too high a fuel pressure, you may connect a gauge to see what you have, and aim to keep it under 3 psi.
 
What he said ^
The spring loaded valve a newer style and work fine.

I had similar problems a few years ago when switching to HIF6’s on my 2000TC. In that case it was ethanol causing it to boil on hot days. I cured it by adding extra self adhesive glass fibre heat shielding to the existing heat shield under the carbs. I’d say this is unlikely your problem as it had to be 88°f (29°c) or higher to happen.
 
Thanks both, much obliged to you. Something for Sunday morning, then if successful, perhaps a drive to a nice country pub for a roast dinner; want to use the old car as much as possible before the rusty weather starts.
 
Well, it's all been fine so far, thirty miles later and some nice lunch. I tempted to say job done, but the problem with intermittent faults.........the biggest difference was in float spindle, old one worn on ends, a bit rattly in the carb, new one snugger in carb and fixed to screw. Float was fine, but replaced anyway. Valve seemed in good condition, replaced anyway. Fingers crossed.
 
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