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MG MGB Technical - Carb springs

I have had my carbs rebushed and on dismantling I noticed there are only 2 springs both on the throttle lever.The heat shield has 3 attachment points and the Moss catalogue shows 4, 2 on the throttle and 2 for the choke. Any advice on how many springs there should be and where they attach; photo would be great.
R E Merrall

Need to know age of car and type of SU's fitted.
Allan Reeling

1975 bgt but with su hs4 carbs
R E Merrall

I have one spring per throttle, i.e. 2 springs. When I got my B it had 2 springs on the carbs. I had to put both feet each side of the choke Knob to activate. Tossed them, as the carbs have return springs which are adequate.

Some folks like a third spring on the throttle, at the end of the cable.

H J Adler

Rod, attached is a picture that may help. I have HIF's so don't have the problem with all those springs!


Andy Robinson

HS4 carbs 3 springs, as per Andy's attachment.
Allan Reeling

Agree - three on the throttle and one on the choke. The choke cable is of the 'under and up' type, with a little tag on the clamp pin for the spring to hook into. There doesn't seem to be a similar tag for the throttle cable, that just seems to hook over the clamp pin.

My 73-heat shield has four holes and a tab, and the two other holes are slotted, whether that's original or not I don't know. The shield itself does look original.
Paul Hunt

Ok, I get to add in another query. What holes do you use? I use 4 springs (one on the choke and one on the throttle and one on each end of the shaft) and note there are holes in the plate and also the small tabs that stick out with holes in them.
Bruce TD4139 Cunha

Bruce I used the 3 tabs that stick up for the throttle and 1 of the holes for the choke. This seems to line up OK
R E Merrall

I only have one tab, which hence could be for the throttle cable or the choke, I use it for the choke. See which spring needs to be stretched less to reach it and I'd use that.
Paul Hunt

as a matter of interest, did you have to strip the carp totally to get them rebushed, or just remove the throttle bits?
Graham Moore

When did they change to HIFs - my 75 came with them ?
Roger Walker

I believe that the change from HS4 carburetors to HIF4 carburetors came sometime in '72. RAY
rjm RAY


I just took the carbs off and took them to local mg specialist, he rebushed and checked them over. Ray is right but po changed them to HS4's don't know why.

R E Merrall

Depends on the market. According to Clausager all export cars got HIFs with 18V engines from August 71 i.e. for the 72 model year. For the UK it wasn't until November 1973 i.e. part way through the 73 model year.

When carbs have to be changed for some reason or major rework is due, HSs are often preferred as they are simpler to deal with, at the expense of slightly more emissions. Which may not be an issue, government-testing wise.
Paul Hunt

This thread was discussed between 17/01/2016 and 12/02/2016

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