MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - SU rebush

I just finished rebuilding my HS4s after the bodies were re-bushed at Burlen. They use steel back Teflon bushes, it will be interesting to see how they last. You can get brass bushes but I used Burlen because they are used to doing this job and the spindles need to line up so the butterfly closes well.
The old spindles had worn and possibly were causing a misfire through weak mixture at high manifold depressions and there was clearly no point trying to trouble shoot it with a known problem.
Has anyone else on here done this job and how did it go?
I always kept the spindles oiled because I would have preferred to avoid this job, hopefully it wont need to be done again for along time.
Stan Best

Hi,

I did this for a carby, for my Wolseley. Daunting to start but it went well.
I've attached details of how I did it.

Herb


H J Adler

Hi,

I have two SU HS2 on my 1275cc midget, and I was looking at this opportunity too.
I just changed my spindles while refreshing my carbs, and they were both clearly worn at the two "pivot" contact with the carbs body.
Just fitted new spindles, but I can still feel a light play along the axis when installed in the body. I don't think it impact the butterfly operation (yet), but putting bushes is definitely something I would do during the next refurbish.

It is interesting to know they use Teflon. I am not an expert in materials, I would assume they use bronze, as the spindles are.

Also, I wonder what is the effect of the dirt getting in, and the benefit of installing any device/cap to prevent dirt entering the pivot....

Can you feel any (light) play still, or it is perfect ? :)

To finish, there is also an interesting topic here with a nice pic, and a PDF explaining how to DIY : https://www.mgexp.com/forum/mgb-and-gt-forum.1/su-brass-throttle-shaft-bearing-options.2259015/


CH Hamon

It's not so much butterfly operation that's affected but vacuum leaks upsetting the mixture balance across the range. In extreme cases as well as that mixture can get past the fully closed butterfly and you can't get the idle down.
paulh4

The action of the butterfly is perfect after the re bush. It moves smoothly with very little force needed and you cant feel any play.
I used Burlen as they already had a jig. They also replace the spindle and butterfly. Although they ask for the carb to be stripped down I took everything else off but left the old spindles in so they could see which one went where, they were fine with that.
Stan Best

I'm not sure what the bush material is, could be Teflon or Delrin. Anyway it's one of those slippery engineering plastics.

Herb
H J Adler

I spread a film of RTV over the exposed spindle end on my Midget. On the B, I slipped a piece of hose over the exposed spindle end. This will protect the pivot surface from dirt blown by the engine fan and greatly reduce spindle and bushing wear. The RTV will not affect spindle movement.
Glenn Mallory

Good idea, it was that pivot that was most worn so I will look for some hose that fits, thanks.
Stan Best

This thread was discussed between 19/11/2019 and 04/01/2020

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.