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MG Midget and Sprite Technical - Refurbishing Carburettor

Hi, I am in the process of refurbishing the midget (1500) and thought I would have a go at the carbs. As can be seen from the pic of one carb, they are in a desperate need of a clean, however is it possible to restore the carb bodies to "as new" visually, myself, as opposed to sending away to be aqua blasted or similar.
Thanks


Kevin Fuller

Not sure if these would pass for factory fresh but this is the result after a few hours of elbow grease, carb. cleaner, paraffin and a little solvol on the dashpots. I'll post a pic of the before condition next.
Bill


W Dunsmore

Before.
Bill


W Dunsmore

Kevin

I undertake quite a bit of motorcycle restoration for which there is a deal of polishing up of engine cases. I would imagine carbs are of similar alloy material so here is what I do.

Degrease everything with gunk/jizer/similar. Scrub it in and rinse off thoroughly.

Initial surface prep. with Scotchbrite pad and T-Cut. Fine wire wool for the more inaccessible places - but take care it doesn't abrade the surface.

Clean it off every now and then to observe progress - I use petrol. You are after a smooth uniform finish.

Wet and dry starting with 400, 800, finish with 1500.

I then use a polishing mop and blocks of grinding paste to buff it up. This could work quite well on the dashpot, but would be tricky on the rest of it.

Elbow grease basically.....

Oggers

You're right about the elbow grease Oggers. Doesn't seem to be any substitute. But personally I don't like the idea of wire wool because you can get tiny particles of steel unobtrusively embedded in the alloy which can then corrode and leave you with annoying rusty stains. It's the same reason I don't use it on wood.

Oven cleaner spray is good for hard "baked on" grunge in awkward places, but be careful how long alloy is exposed to it - it's pretty aggressive.

BTW - nice job Bill.
Greybeard

You can buy chromed dash-pot covers for the lazy solution - but they make the rest of the carb, float chambers etc look even worse by comparison! Those spray on carb cleaner solutions are pretty good, especially for cleaning up all those awkward corners and crevices when assisted by paint and toothbrushes. Electric toothbrushes are also useful for this sort of thing!
GuyW

Grey

Fine wire wool is fine as long as you clean off the residue with petrol. I wouldn't use oven cleaner - far too alkaline and will corrode/stain any aluminium based alloy almost immediately. Brake fluid seems to work pretty well though - but again, clean it off before polishing/buffing.
Oggers

Kevin,
be very careful about cleaning the inside of the dashpot and the piston as they should match each other as a set and have close tolerances, clean them with petrol on a cloth and only put oil lightly on the rod part of the piston and no where else.

Personally I've gone off wire wool because it sheds small bits you don't always see, I'd try the synthetic steel wool pads 000, even plumbers have been using them for quite a while and they're a very (small c) conservative group.

For the final polish I'd use a liquid polish, metal polish or whatever.

Somewhere on the net is the SU Tuning book to download and your Driver's Handbook will also help with setting back up.

Also there are a load of John Twist videos on carbs, including matching the chambers to pistons, needles & seats, tuning, etc..
Nigel Atkins

"I've gone off wire wool because it sheds small bits you don't always see"

You can feel them, though...when they are embedded in your fingers!
Dave O'Neill 2

have used synthetic steel wool when I stripped the paint off a WW II Avenger. Did a pretty good job as well combined with the paint remover.

If you are going to use petrol as a solvent, be very careful. As you know, the stuff ignites very easily and petrol fumes are heavier than air so settle at the lowest level.

If you must, do it outside, away from any ignition sources and keep an extinguisher very handy for that "oh no!" moment that hopefully never happens.

Clare
Clare Ravenwood

Economy tip for ya - use worn washing up scourers, green or the white (non-scratch?), particularly the ones with sponge attached as they're easier to shape with and you can use the dampened sponge side to wipe off the muck caused by scouring and see your progress.

If like me you do the washing up then you can decide how worn (or course or fine) these will be before being used for cleaning/polishing metal.

Also 4-sided, sponge block, nail buffer blocks, four different levels of filing/polishing. I've used these very effectively on metal and other materials. You can get them from 29p each up to over £4 my wife tells me. The more expensive ones are more durable and often better at the job but you can get fourteen 29p blocks for the price of a £4 block - and the more expensive ones are not given up so freely.
Nigel Atkins

Many Thanks for the tips
Kev
Kevin Fuller

HI,

Don't have any pictures to hand but I did an initial clean / degrease then used a dremmel with a small polishing kit from halfords and a polishing compound, trying not to polish it too highly...

Alan
a reid

The carbs are now clean enough to dismantle for a proper clean & refurb, carb cleaner & tooth brushes works wonders


Kevin Fuller

This thread was discussed between 26/03/2017 and 27/03/2017

MG Midget and Sprite Technical index

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