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MG Midget and Sprite Technical - Carb balancing

After trying for 2 1/2 hours this afternoon i have had to conceded that i must be doing something wrong, followed manual but cant seem to get them right is there anyone local to Preston lancs who would be willing to demonstrate / instruct in how to adjust them.Failing that is there a mobile mechanic in the area that you could recommend last job before the MOT.
mark 1500 nearly on the road

carbs come at the end of the chain of checking/setting up in this order - tappets, CB points, plugs, timing, carb mixture

if you adjust any item in that chain them you may need to check the items that follow in the chain

don't worry I am getting there but you do need the correct steps in place to set the carbs up

the dashpots and their pistons need to be matched - 41 Matching SU Air Pistons - http://www.youtube.com/watch?v=IfU47Oqq9wA

principles of setting here - 147 MG Carburetter Tuning - http://www.youtube.com/watch?v=4nvGLgO6pj0&feature=plcp

and here - 35 Tuning HIF Carburetters - http://www.youtube.com/watch?v=ASeMfXfjNpw&feature=plcp
Nigel Atkins

if they don't set then there could be faults or wear

these might help -
123 MG Carburetors & Doors (first part needles and seats, springs and carb oil) –
http://www.youtube.com/watch?v=v9QI3NlvwiY&feature=plcp

Needle and seat - http://www.youtube.com/watch?v=pVX_JClyeDQ&list=FLr4Udxf9e9Cq7fxH4V23MWQ&feature=mh_lolz

Setting the Float Height - http://www.youtube.com/watch?v=82YNx-RkGNI&list=UU40j4KqUJPMVv4FQ29ro-xQ&index=11

for background info -
44 Secrets of the SU Carburettor Part 1 of 2 - http://www.youtube.com/watch?v=7GRAcqDySog&feature=plcp

43 Secrets of the SU Part 2 of 2 - http://www.youtube.com/watch?v=60Bj_2cZQnc&feature=plcp
Nigel Atkins

Right took carbs off to check if everything ok ,PO said he had refurb carbs but looking they have new THROTTLE SPINDLES but play in them bushes not changed, ordered some new bushes, front carb more wear than back would explain difficulty in balancing done all other things timing etc hope this is the problem
mark 1500 nearly on the road

Mark,

Do you have bushes in your carbs ? most originally ran direct in the alloy casting.

Putting bushes into the carb bodies where not fitted previously is not that simple as correct alignment is essential.
Burlen do not recommend drilling right through, so you have to bore from both ends.

Just done a very old H4 set for a TR2 and it took ages to set up each time - finally quite a good result using a small lathe and a slot drill.
I would have prefered to line bore with a boring bar between centres, however its too small for the bars I have with adjustment screws.
Drilling straight though in a lathe and locktighting would be simpler option even if not recommended.

How do others go about fitting the bushes ?

R.

richard boobier

There's a method described here on how to use a hand reamer but the wrong way round so that the shaft acts as an alignment guide. Nice write up on it too!

http://www.chicagolandmgclub.com/driveline00/1001/jasw.html
Guy W

Yes there are brass bushes in seems to be just one end that has movement in it going to get them bored for new bushes.Also should there be some sort of seal on the jet bearing in the groove see pic.

mark 1500 nearly on the road

I rebuilt my HS4s by using the link guy posted but I used a old keyless drill chuck as a handle to do the reaming

It worked great...1 carb down 1 to go

Prop
Prop and the Blackhole Midget

Ensure that the needle is correctly centred in the jet - it's a 5 minute job - but absolutely crucial. SU manual tells all....
Mark O

Not trying to spannerise the progress so far but :-)

My balancing problems came down to a simples (one return spring is duff). Now even with that playing up and running rough she went through the MoT OK.

As I had problems getting to the point of being on the road, and getting mighty fed up with more problems arising as I kept working on her, in the end I just took her down and after a two day fettle on things other than fuel related stuff she passed. Since the MoT the driving has 'settled everything' and the other things that have happened have been more significant to the running than the carbs. So my advice would have been does it look like it will pass? If yes take it, and then have the time to sort everything as you add the miles :-)

BTW find a tester that is knowledgeable about classics and the MoT requirements for them.

A happily driving leaky engined 1500 driver; Dave.
Dave Squire (1500)

good point by Dave, the MoT has very little to do with a car running well it's about the car passing a minimum standard to one trained person's opinion at that precise time

as regards the carbs as long as it passes 7.3 B of 'Inspection Manual for Classes 3, 4, 5 and 7 Vehicles' here - http://www.transportoffice.gov.uk/crt/doitonline/bl/mottestingmanualsandguides/mottestingmanualsandguides.htm

once you've got the MoT as Dave has put you can set above getting the whole car including the carbs running well - it's the same as learning to drive after you've passed the test
Nigel Atkins

checking the rest of the fuel system i found cracking in the out side of the flexible fuel pipes , only been on car 2 years think it is just the outer cover ,tubing is SYTEC DIN73379 type E NBR/CR so good quality, is this just another example of poor modern rubber.
mark 1500 nearly on the road

I've used Goodyear 6mm petrol hose on mine since having trouble with 1/4" fuel hose and the 6mm fits better!

rubbish rubber ! I've got no idea what you mean


:)

steering gaiters, TRE boots, fuel hose, wiper elements, door seals, windscreen seals, etc., etc. :(
Nigel Atkins

according to spec outer Synthetic CR Rubber
(Chloroprene Rubber) inner Synthetic NBR Rubber
(Nitril - Butadiene Rubber) so hopefully inner ok,
mark 1500 nearly on the road

Mark,
For my MOTs and complicated stuff I take my 1275 to The Mini Centre in Preston. They're near the Continental pub by the river. They're always helpful and enthusiastic.
Ask for Carol-Ann, 01772 251189.

Mark
M Crossley

Yes i know where that is I use howarths on raglan street very helpful, always has a mini rebuild on the go.
mark 1500 nearly on the road

This thread was discussed between 01/08/2013 and 06/08/2013

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