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MG Midget and Sprite Technical - Do I need a smaller carb?

I had a great day last Saturday at the Aldon Automotive rolling road - courtesy of the MGCC midget Register. My Midget got a few complements about the way it ran but the techie doing the diagnostics said the piston on the HIF44 was only lifting the needle around half way (which made setting up a little difficult). He suggested that a smaller card (HIF38 or a 1.5 SU) would increase airflow and be better. Anyone else here use a HIF38 or similar and with what result?
My engine spec is around 1300cc (+30 overbore), ported big valve MG Metro head, Maniflow LCB, K&N BUT standard camshaft.

I know, I know - I need a hotter cam!
Chris H (1970 Midget 1275)

Chris,

Sorry can't help with the query but I thought a pic of the moment would be nice.

Agreed great day and thanks to MGCC for organising.

Mine it appears has a fautly dizzy - roll on santa claus !

R.


richard boobier

Try a weaker spring...

A
Anthony Cutler

HIF44 was standard 1300 MG Metro fitting and isn't too big for a 1275 Spridget. I'm surprised that Aldon would suggest that.

I think Ant is probably correct - more of a DCOE man myself....
Daniel Thirteen-Twelve

Yep bit surprised by that comment also. However many SU carbs do NOT get the piston lifted fully due to the spring (one reason) being too stiff. Another reason why smoothing the edges and messing is a complete waste of time and energy.
I'm with Daniel get a DCOE.
Robert (Bob) Midget Turbo

Wow Richard. A great photo. Could you send me a copy at chris dot hasluck at blueyonder dot co dot uk.

It was a great day and I would recommend using a RR to anyone wanting to learn more about how to set up their car.

Chris
Chris H (1970 Midget 1275)

Hi Chris,

It was a very interesting day, heres another pic, I've also got a video clip, but its too big to email at the minute, I will try to resize it for you though, your car sounds really good on the clip.

John


John Collins

Very strange request by Aldon, the HIF38 was mainly used on the 1000cc Metro. The 44 is definitely the one for a 1275. As well as the spring being too strong, the needle could be wrong! Also, has the needle been fitted correctly?
Cheers John
JOHN HALL & JULIE ROBERTS

Is the butterfly opening enough with the full pedal movement? Easy to check with the help of a friend and with the airfilter off.

I even use a HS6 on a 1098 engine.
Bas Timmermans

you dont need a smaller carb choke diameter

wonder what Aldon need?

bill sdgpm

This thread was discussed between 24/11/2009 and 25/11/2009

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.