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MG MGB Technical - Float level settings

I am trying to adjust the float bowls on my HS4 SUs. The old valves were slightly different and worn, so I obtained two new ones - with Viton tips.
Now to adjust the position of the floats I reviewed the literature.
One diagram (bottom right from Speedsport manual,is similar to the Haynes manual diagram and shows a straight float arm. The other (from MG Experience site) is unclear about the float arm, but the float is clearly at a significant angle to the bowl. On my bowls, the float is held quite "high" with the new valves, and to get the gap to 3/16" would involve quite a bend and the float would be at quite an angle (like the LH diagram).

So, for a "bent" float arm, is the 3/16" still the right measurement? The current gap is more like 5/16".
Is it more critical that they both floats are in the same position (ie the fuel levels will be equal, albeit at a lower level) - or will a lower level cause low fuel flow problems?

Or should I have floats with straight arms as per Haynes manual?


John Minchin

John-
There are no straight arms, they all are Z shaped. But, the Z is comprised of three straight sections with 90degree bends between them. Yours is mangled. At least, the section riveted to the float should be flat, as should the part adjacent to the pivot. All adjustment is at the "90deg" bends. It also looks like the pivot section, which can't be seen, is bent so that the pivot "hole" is not centered on the arm.
In any case, the float level is very far out. The top of the float is not flat, but a flat cone shape, and the edge away from the pivot should be approximately parallel to the lid, which will give the requisite 1/8-3/16". Note that there is no washer under the float valve (I've met a few!), which would affect the float height drastically.
AFAIK, the only new floats available have no arm, but are all nylon and cannot be adjusted, short of machining the shoulder of the valve and/or fitting shims under it.

FRM
FR Millmore

Yes they have been bent a bit out of shape (not by me I hasten to add)
With as much care as possible to avoid damaging the floats, I managed straighten and rebend the gloat lever to get the required 3/16" spacing, with the pivot free but not too loose.
With floats back in and new valves, the fuel pumped until the float was full and there was no overflow and no leakage through the jets. The pump was still clicking more than the requisite 1 per 30-40 seconds, so there must be leakage back through the pump. At least I seem to have stopped the fuel leakage that was a bit concerning.
John
John Minchin

FRM-
Burlen Fuel Systems is marketing new adjustable height StayUp® floats for the SU HS2, HS4, HS6, and HS8 carburetors, are resistant to modern ethanol based fuels and has a military specification closed cell construction that makes it puncture proof. The ability to adjust the float arm allows for quick and easy minor alterations to float levels where required.
Stephen Strange

That's good news, hope they make HIF ones too!

FRM
FR Millmore

This thread was discussed between 07/12/2011 and 08/12/2011

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