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MG Midget and Sprite Technical - Backfire...

Hi,

I've finally finished swappng over the head gasket in my 78 midget. She's been SORN'ed since Sep last year - the joys of having no time.

Reassembled it all and tried to start her up. However, I'm getting a backfire on cylinder 3 or 4 (judging by the vapours exiting the carb (i haven't reattached the air filters or exchaust maniford yet!)

Any ideas what the problem could be - long shot as I guess it could be a lot of things.

I'm also thinking I might of reattached the carbs incorrectly as they didn't seem right (the choke attachment bar seemed strange) - anyone got any photos of how this should look?

Many thanks
Mat
M Andrews

Check to see if your plug wires are going to the right plugs. Crossed wires is the usual cause of this problem.
Martin

Those of us west of the pond tend to take a while learning that the dizzy spins widdershins. The only difference is that the wires for two of the cylinders (2 and 3) get reversed. Double check these.
David "BTDT" Lieb
David Lieb

As has been stated, check the spark plug wires. Firing order is as follows: 1-3-4-2 distributor rotor moves counterclockwise. (For those of the digital watch era, that's to your left as you stand directly looking at it when it turns.)
Clive Reddin 76 Midget

besides the dizy being wired wrong I have had back fires into a carb cause by a lean mixture.
Stefan

Thanks for all your comments. I've found 2 potential problems!

1) Attached the carb all up,seems the manifold might not be 100% tight as the backfire is shooting vapour upwards though the gasket.

2) The dizzy seems to be wired up with 1-2-3-4 !!! strange! I'll set all the dizzy up from scratch via the TDC mark.

Hopefully that'll fix it - else I'll be contacting a mobile mechanic - the weather is nice and I want her out again!

Many thanks
Mat
M Andrews

You mentioned the carb linkage didn't seem right. Is it possible that the linkage could have prevented a good seal, causing a lean mixture as Stephan suggested? Is the backfire only from the carb or from the tailpipe?
C. J. Charvet

Mat has already told us the ignition was 1234 getting 1342 shouldnt take more than a few seconds and ought to do the bizz!

must be enough to go on with

I expect the manifold sealing would help it get better when sorted though too
Bill

This thread was discussed between 24/07/2008 and 27/07/2008

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