ariel square four carb

[p tuxworth]

im not happy with the solex carb on my square four , has anyone a SU for sale or can anyone give me a good starting point for fitting a Amal concentric / mono , the engine is a all alloy 1951 and i feel more at home with these carbs , the solex is quite alian to me , thanks

[brenton.roy]

Hi, I remembered reading this a few years ago, from Micko Small. It talks about slides sticking because of the the constant suction with a square four.
http://www.barkshire.co.uk/AOMCC/Knowle ... spx?id=226
Brenton

[nevhunter]

It's quite likely the slides would tend to stick. With only one carburetter you could increase the spring tension a bit and a bit of 2-stroke oil (Egg cup to a tank at the most) will reduce the wear and help in the sticking problem. You don't need a very big carb on a SQ4. Nev

[david.anderson]

you cannot fit an SU carb to a MK1. In order to fit the SU to the MK2 the height of the frame was increased ie the dogleg.
David

[p tuxworth]

this is the dog leg frame with a earlyer engine fitted ( bitsa ) thankyou But has anyone done this and can give me a starting point

[brenton.roy]

Nope, haven't used a different carby, but below is your current jetting. It's probably equivalent to a 250 or 350 single (which makes sense). There is only one cylinder working at a time. The NG uses about a 120 main.
If using a concentric, you'd want the small series, equivalent to your inlet port size.

First number 1938-52, second number 1953
Choke tube 23 23
Main jet 120 120
Air correction jet 150 170
Pilot jet (Auxiliary) 070 060
GA jet (Bi-Starter starter jet) 30 30
GS jet (Bi-starter air jet) 100 100
Well 5.1
Jet cap 51861/L2 51861/L2
Needle valve 2 2

The bit I don't know is the effect of the almost constant pulses of intake.
Maybe start with the 120 main, standard needle (middle notch) and your 70 pilot from below?
Can't help with the SU. I guess you just look for an Ariel one.
Brenton

[p tuxworth]

thanks been offerd a SU carb off a morrice 1000 , i may give that a try . thanks for the info

[brenton.roy]

No worries for the info, but I don't think it will fit in the frame.
I have a couple from Morrie sidevalves and they are taller - the pot is longer (or the body higher?) - they are in another shed. I was looking at them a week or so ago and they are definitely different to the square four type.

[nevhunter]

The choke action on the SU may be a problem. You have to pulll hard and for a fair distance. With a CV carb.( SU Stromberg or Bing etc), you CAN run a bigger carb because the dashpot slide will only open as much as the engine breathes. If the carb is too small it will run too rich at the top end. Nev

[p tuxworth]

not sure what your saying there nev , i have been told SUs will run on there side so this may be an option ? still waiting for it to arrive will post pics if it works thanks again