Fuel starvation

[Terryb]

What would cause fuel starvation on one cylinder on a 62 A10 GF. It has an Amal 389 carb and when kicking it over, I’m getting the occasional kickback and on inspection the No.1 plug is wet with fuel and the No.2 dry?

[limeyrob]

I recently had a misfire and one wet and one dry plug.  It turned out to be a weak spark on one cylinder and swapping the mag cured it. The carb idle circuit was also partially blocked (a Concentric) so there were a few things to work through.

[Terryb]

Yes, I suspect the pilot circuit. So I’ve taken the carb off and will work through the internals.

I’m also going to check the timing again. Looking at the sparks, the No.2 is weak, compared to No.1. But can’t see how that impacts the fuel sharing 🥴

[limeyrob]

If one cylinder has a week spark it will not affect the mixture, what it will do is cause a wet plug because the fuel is not being ignited on some strokes. I would work on the mag/HT/plug first, then the idle circuit.

[Swarfcut]

 Anyone remember the story of GB's  fuel gnomes and their buckets? Struggling down that inlet tract they can see light from the cylinder with a good spark, so more are drawn to the light. In the none firing cylinder they just spill it in the dark. Easy really.

 I won't sign this one.....

[chaterlea25]

Hi All,
I have read and heard about "induction bias" on A7 /10 's and not sure I believe that it is a "thing" rather than some other reason causing lean/rich problems 
A couple of years ago  rebuilt an Ariel Huntmaster engine and noticed that the split in the induction tract is not finished to a "V" edge where the ports divide. It looks like the port divide was finished with an end mill 

John

[Rex]

Definitely a more likely cause than blaming the idle circuit...which feeds both cylinders!

[JulianS]

If induction bias then this is for the very brave....................

Anyone tried it or heard of it being tried?

[Triton Thrasher]

What would cause fuel starvation on one cylinder on a 62 A10 GF. It has an Amal 389 carb and when kicking it over, I’m getting the occasional kickback and on inspection the No.1 plug is wet with fuel and the No.2 dry?

If this is just when trying and failing to start the bike, I don’t think fuel starvation or induction bias are relevant.

[Swarfcut]

 Why won't it start?

 Just crap in the Carb.

 What, now? Well OK, but only you think it would really help!

 Swarfy.

[Topdad]

Didn't BSA have a special spacer made of tuffnel  that actually was angled you could fit to cover b0th sides

[RichardL]

If induction bias then this is for the very brave....................

Anyone tried it or heard of it being tried?

Very interesting. So, Julian, considering the depth of your collection, you wouldn't happen to have Hap Alzina's dynamometer test results, would you?

Richard L.