The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Amal, Carburation, Fuel => Topic started by: Spayne on 27.04. 2015 17:45
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Hi all I got a problem with my a10 flash 1961.it has a problem with spitting back on opening the throttle from tick over.ive fitted a new carb checked the timing checked the tappets and points everything is spot on,and I've put new plugs in as well.has anybody got any suggestions how to cure it please.
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How did it perform with the old carburettor?
What carb have you fitted?
It's usually a weak mixture. A common cause is an air leak at a manifold joint. Spray the joints with WD40 while it's idling and listen for a change of engine note.
If it's not that, suspect a too-big slide cutaway, or a too-big carb, or a blocked main jet, or water in the float bowl.
It can also be a failing magneto.
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G'day Spayne, I fully agree with TT. Try turning the pilot screw in 1/4 to 1/2 a turn.
Cheers
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as muskrat said,try the pilot air adjusting screw,it sort my similar problem
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Thanks for the replies,the carb is a brand new 389 monobloc set to the book.it did the same with the old carb so I'm beginning to suspect the mag.
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Don't believe everything you read, especially haynes. Have a fiddle with the pilot screw, or see if it improves with a bit of choke.
Then if no good we'll look at the electricks.
Cheers
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As you rev it put a finger over part of the cutaway to see if that stops it. Everyone blames magnetos for some reason. An expensive experiment at 400 bucks a reco.
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Had a similar problem on a brand new Amal. Changing the pilot jet from a 25 to a 30 (or was it a 35? Ouch, the old memory...) cured it.