Monobloc

[Bunners]

Evening All
I am the proud owner (tongue in cheek) of a 1960 Scottish, it is fitted with a monobloc carb, this is fitted straight to the inlet manifold and lies at an angle, I now have a swan neck manifold which will put the carb level is this a good idea? surely the float level would be incorrect if left at the angle it is now. Your thought would be welcome.

[John Wakefield]

Yes better to have the carb as level as possible, presumably the swan necked manifold is for the original Villiers S25 carb so you will need to buy or make an adaptor to fit the Amal monobloc. In my opinion you would do better to fit a Villiers S25 carb as these are more suitable for trials. The monobloc was only fitted to the scrambles engines.

[John Pattinson]

Monobloc

Sounds like you have a 34A scrambles barrel, Bunners! John P.

[John Wakefield]

34A barrel/carb

Here is a 34A barrel fitted with an adapter for the Villiers S25 carb, downdraft angle not steep enough to upset carburation

below is the standard 32A set up with S25 carb

[Bunners]

carb

Evening all thanks for the replies, hopefully I have attached a pic of my inlet set up.

[John Wakefield]

Evening all thanks for the replies, hopefully I have attached a pic of my inlet set up.

Its a made up or after market manifold with what looks like a 389 Amal carb 1 3/16 inch carb, too big for trials, The cylinder is a 32A to which the swan neck manifold will fit but this has round clamp type carb fixing as in the pic I posted.
My advice is to fit the correct swan neck manifold & a S25 carb. The S25 is a simple carb good for trials characteristics. The bigger Amal 389 was used on the 34A scrambler to give more top end performance, as Villiers did not manufacture a larger than 25mm carb themselves. The 34A barrel had larger ports to match up with the Amal carb, which was flange fitted directly to cylinder.

[Bunners]

monoblock

Thank you John, I will look for the correct carb, or adapt the swan neck, I certainly have no intention of taking up trials again at my age & state of health. so road set up with more top end might just be the best option.

[John Wakefield]

Thank you John, I will look for the correct carb, or adapt the swan neck, I certainly have no intention of taking up trials again at my age & state of health. so road set up with more top end might just be the best option.

I still think an S25 carb will be better for road use, the 32A barrel is ported for that size carb so just putting on a bigger carb (Amal 389) on will not give much more power, maybe less. To get more performance you would need a 34A barrel, so might be worth looking for one of these, the 389 would bolt straight on.
If you do get an S25 carb the jets/settings are as follows for the 32A:-
Main Jet 140
Pilot Jet 35
Needle 3 1/2 set out 1.85"
Throttle slide 4
The correct carb would be an S25/2 or S25/5

[Bunners]

monoblock

All very good info John, thanks for that, I will see what I can find.

Ted

[aa will]

hi ted after sorting out my scottish i have a few incomlplete s25 carbs one even has the boss for a tickover screw, i have enough bits to build a decent carb except the slide , if any of this is of interest pm me , or call me on 01362 667859 (answerphone) will.