Morris Minor Owners Club

I'm pretty sure my SU isn't all that happy.

I did check the float when doing the 6k service and re-set it to the prescribed level, but Hebe isn't too happy when she's cold. (needs a lot of choke and about 45 seconds of driving before she's happy and has much power).

Yesterday in the terror which was the Hangar Lane Gyratory (solid solid traffic for about 50 mins) she was perfectly fine with the water (didn't loose a drop - horay! ) but after a while was starting to sound a bit uneven on the tickover until we got on the move again (she also juddered a bit until we got going) - almost as if the fuel was too rich?

When she's actually going, she's fine. The fixed speedo (I completely dismantled and cleaned mine) now reads the right speed and her ride is a lot better (now the suspension is sorted).

Question is...
Should I play with the idle speed? Or do I dismantle the SU (is it easy?) and clean it...

Or, just wait for my local garage who are going to "tune" her at the end of the month, on the whole "if it ain't broke don't fix it (Ie, she works so don't play) " mantra...?

She's also started running on a bit after turning off... so I suspect it's the mixture...

Nikki

solid solid traffic for about 50 mins)......... .............she also juddered a bit until we got going) - almost as if the fuel was too rich?

If the 2 things were coincident, then they may well be related. 50 mins of solid traffic on a warm day is enough to give most Minors a problem with fuel vapourisation.

Hi Ray

Yeah... that sounds about right then


I just had a play, and I've re-set the mixture to 12 flats down... seems ok

I did notice though that there is some fuel evaporation from the SU - I wonder if I'm missing a gasket between float chamber reservoir and the chamber top...

Nikki

Yes there should be a gasket on the top of the float chamber bowl
you should be able to see if it is present. It does not prevent
petrol from leaking under normal circumstances, because the level of fuel should never reach
the joint but it will prevent loss of fuel vapour. if the float needle
is faulty then excess petrol should emerge from above the actual float
chamber lid, not from the bowl itself.

Hello MP,
if you really want some good S.U. information you can't do better than Burlen Fuel Services' S.U. Reference Catalogue. This list all the spares, maintenace, overhaul and setting information for carburettors and fuel pumps. I have found it invaluable even if it is not particularly cheap.

Alec

cheers Alec - I'll look 'em up once our guests have departed... er... gone

Here you are Nikki
http://www.burlen.co.uk/

ooooh thanks Kevin!

Triple SUs... Hmmmmm.......... Complicated........ *droooooooools*

Minors are a bit down on power when cold - it's very noticeable when I leave for work that (when already warm) my Minor hits 60mph much more quickly than when cold. This is one of the areas when fuel injection assists modern cars.

I fiddle with the engine idle screw every Autumn and Spring - to slow the revs down in Summer and speed them up again in Winter. It works fine except on long Winter runs where I need to slow it down after the engine gets hot.

Just for added information - Haynes also publish a workshop manual that covers SU type H,HD,HS and HIF to 1988. Haynes reference 299.

Also very useful - http://www.moreg.org.au/carburettors.htm

This is one of the areas when fuel injection assists modern cars.

That's one of the benifits of the later HIF type SU as they have a bimetalic spring the allows them to compesate for different temperatures..

Hello Iain,
don't forget that the later HS had a waxstat jet, supposed to compensate for temperature, although I believe that it could be troublesome.

Alec

I believe that it could be troublesome.

I have heard that as well but thought the waxstat was only fitted to the earlier HIF`s

I had a waxstat carb on my '85 Mini and it was fine. I think there was one on my '79 Mini too.