Spitting back

[Spayne]

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.

[Triton Thrasher]

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.

[muskrat]

G'day Spayne, I fully agree with TT. Try turning the pilot screw in 1/4 to 1/2 a turn.
Cheers

[Derby Rob]

as muskrat said,try the pilot air adjusting screw,it sort my similar problem

[Spayne]

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.

[muskrat]

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

[wilko]

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.

[morris]

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.