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MG Midget and Sprite Technical - weber problems

So,
car now misfires at gentle throttle. I can accelerate through the misfire.
When I do, she goes like a bat out of hell but at constant light throttle pressure she misses really badly.
Yes its the carb, I know that.

Weber 45
'73 midget


Mallorcaben

Sorry Ben but do you ever get any of these problems resolved, never heard any feedback?

This one sounds like weak mixture but shouldn't simply happen without reason. The beauty of a weber is once set forget about it.
Bob Turbo Midget England

Maybe water or some other debris has gotten into the idle circuit and is causing a blockage and making it run lean.
David Billington

Hey Bob,
no I'm absolutely sick of it. Taken about 2 weeks for me to muster up the enthusiasm to take her out again.
After 10 months in the garage, the misfire problem has just "moved"
Its times like this I wish I was in the UK. Could just pop her into a garage & get it sorted.
I would love to try a diff carb on her, or send mine away to be correctly set up.
hmm, there's an idea actually!
On hard throttle though, shes running better than she has in years! (probably because Ive replace the float that was broken off!)
Im 90% sure the garage have not set the Weber up correctly.
You got facebook/skype etc Bob?
Mallorcaben

http://www.facebook.com/album.php?aid=16261&id=560545007&l=c8219c071a
Mallorcaben

Hi mate I certainly feel for you.

Couple of things you have mentioned there is the float broke off.

This can cause problems and it is good that you have sorted that out, however it seems that that has changed the tuning of your weber.

You say that now the thing performs well on hard throttle and is poor on low throttle openings?

The weber uses primary jets for idle and low throttle openings and Main jets for high power high throttle usage.

Seems to me that it is now possible that the high power circuit (main jets) are correct and the primaries are weak

This can be as a result of the float being repaired as before with the float being faulty the mixtures would have both been extremely rich.

What you need to do now is tell me what size the primary jets are please.
Bob Turbo Midget England

air filter case is too shallow and ram pipes, assuming you have them, will be to short.
Daniel Thirteen-Twelve

I have a dellorto fitted (v similar to the weber). The carb was fitted by the PO. When purchased the car had the exact same fault you describe, a misfire at low revs that could be driven through, after about 2500rpm it went great.

Strip the carb to get all the exitsing idle / main jet / tube / choke details etc if you dont have them already, e mail them to Eurocarb with a brief description of your engine - cc, exhaust, cam etc and the details of the misfire

Euro carb suggested alternative part numbers by return

The parts were sent next day, fitted in an hour and completely resolved the misfire.





S G Macfarlane

found the problem, started a new thread called Weber manifold
Mallorcaben

I still think you need a bigger air filter and decent rams!
Daniel Thirteen-Twelve

This thread was discussed between 04/01/2011 and 12/01/2011

MG Midget and Sprite Technical index

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