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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 Midget and Sprite Technical - S U carbs

Hi all is there a specific oil to put in the dashpots on su carbs ( hands up im not really up on su more a weber person )?? my reason for asking is I put my etype back on road after a 3 year lay up over weekend, I restarted it sympathetically ( oiled bores , spun over without plugs in until oil pressure come up etc ) but while out for a drive yesterday my mate behind could see a constant swerle of blue smoke under accelleration ( wasnt like that before the layup ) ,i was thinking oil control rings gummed up ?? or have i over oiled the carbs ( used 20/50 in them ) what stops the oil in the carbs being sucked into engine by the engine vacuum ?? cheers for any ideas
Darren 2 litre frogeye

Darren.

In my opinion, 20/50 is too thick therefore make the mixture a little too rich on acceleration.

I use 3 in 1 oil, nice and thin and works well for me.

Buy with the E, I would give it some time and give it a good long run to warm it up properly and blow the cobwebs out of it, then set up the ignition and carbs.....

Mark.
M T Boldry

The Spring 2009 issue of “British Motoring” arrived in my morning mail – and despite this “publication” serving as a consumer marketing piece more than anything else, as luck would have it, there was a one page article about SU carbs by author Robert Goldman (whoever he is…).

On page #3, it appears that the author is actually testing some type of O2 sensor product but in the process of torturing the SUs on a MG midget – surprisingly the engine response was rather unphased. To me - this seems to put into perspective the dabbling & babbling that others have experienced regarding their own witches brew of multi-weight oils, Auto Trans fluid, Guinness beer and/or other precious fluids.

Never having done a scientific test of what works best for my 1275 engine – I use 20/50W Castrol or whatever is left over from the previous oil change. Therefore, it would appear that other engine tuning issues (compression, ignition, valve adjustments, etc.) might be much more important on driveability relative to what the optimum “secret sauce” might be to use in the SU carb.

Bottom Line? I am a big fan of the SU carb design. Simple to setup and quite cheap to maintain. Yes - an occasional replacement of the butterfly spindle or possibly the replacement of the spindle plus new bushings will likely keep your little British car on the road for a long time to come. Out my way - the real issue is keeping that pesky tin worm at bay in North America.

Just my 2 cents worth…

The hyperlink to the article:

http://www.britishmotoring.net/

Mike Pelone

My 2 cts: I filled up a set of SU's of a borrowed car with 20/50 and from that point on there was a little lag in acceleration that wasn't there when before I filled them uip with 10/40.
Defenitly too thick. I also used to put ATF in my twin-SU'd Volvo Amazon, as advised by the dealer.
Alex G Matla

ATF is good too....

Mark.
M T Boldry

I've got a little bottle of Penrite "Damper Oil for SU Carburettors".

http://www.classic-oils.net/penrite.htm
Nick

This thread was discussed between 20/04/2009 and 21/04/2009

MG Midget and Sprite Technical index

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