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MG Midget and Sprite Technical - Hesitation

Hello all.

This morning I detected a hesitation at around 2,500rpm on load.

I have a 1275 & single HIF 44 with an electronic dizzy from Simon BBC.

I have been running this combination with a redtop rota for several years without any problems.

I have removed the suction chamber from the carb and the needle looks true & undamaged.

On removal of the plugs all 4 were very sooty black - quite unlike the light tan I am used to.

I would welcome suggestions as to how I should proceed from here.


Thanks.
Gavin Rowles

Easy things first. Check air filter isn't clogged, float height is correct, or float itself isn't leaking, damaged or fouling the body thus messing up the fuel level. Check float needle and seat whilst your are there. IRRC on the HIF 44 it is imperative that the air hole? on the flange on the filter side isn't blocked up - by loose gasket material or some such. Next obvious thing is mix is off for some reason. SU manual on web somewhere - simple enough.
Oggers

Trying to remember something Iíve read/heard about the HIF having an o-ring which fails, causing rich running etc. Possibly due to ethanol?
Dave O'Neill 2

Thanks both.

Will get the carb off & take a look at the SU site.
Gavin Rowles

Before disturbing the carb I would check that the choke cable and cam are returning fully when you push in the control knob.
GuyW

The HIF carbs have a valve choke, the body of which can erode and allow extra fuel through.

If I remember correctly there are a couple of screws holding the choke valve in place, easy enough to remove and check.
Chris at Octarine Services

But make sure you align it properly when reassembling. The flange of the valve body has a little cut-out which should align with either screw. We have found misalignment on a surprising number of cars. This can result in the choke being off when you think it's on, but worse still on when the choke cable is fully in.

Dave, I don't think it is ethanol, just old age. We don't have much ethanol here and it was an issue well before ethanol was introduced.
Paul Walbran

This thread was discussed between 14/05/2019 and 17/05/2019

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.