Author Topic: SW5 Carb settings  (Read 3178 times)

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Offline zacgrief

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SW5 Carb settings
« on: 27 Jun 2012 at 21:15 »
Gents,

See below a picture of my SW5 carb, I didn't establish which model Amal it was but I think its the fairly common soldered variety.

Its running pretty rich at the moment and I think the idle mixture is controlled by the adjusting screw in the picture, am I correct in that screwing it in will richen the mixture? The carb also has a choke/ mixture control in form of a vertical rectangular slot with a plunger inside. Am I correct in thinking that when the plunger is blocking the slot this blocks off the air, so richening the mixture and weakening the mixture is by lifting the plunger?

Cheers

Zac

« Last Edit: 27 Jun 2012 at 21:59 by Dave »

Offline Ian

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Re: SW5 Carb settings
« Reply #1 on: 28 Jun 2012 at 01:01 »
For Amals you are correct on both counts - screw in idle mixture to make richer - and choke is off when retracted. Basically (with some variation) the mixture relies on the idle screw to maybe 1/3 throttle, needle jet to 2/3 and main jet to full. Cutaway is important as well.

Offline zacgrief

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Re: SW5 Carb settings
« Reply #2 on: 28 Jun 2012 at 07:33 »
Ian,

Thanks, my carbs only have main jets, no idle jets and no needles. I assume they must be track versions as they also dont have a slide stop for the bike to tickover. I will try and adjust the air screw and then I will have to reduce the main jet size.

Cheers

Zac

Offline zacgrief

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Re: SW5 Carb settings
« Reply #3 on: 10 Jul 2012 at 06:32 »
All,

I was looking at a 1926 TT at the weekend and apart from the fact that its carb had clamps and mine has soldered joints they are identical.

Cheers

Zac

Offline eddie

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Re: SW5 Carb settings
« Reply #4 on: 10 Jul 2012 at 07:32 »
Zac,
       As your carbs have no needles or needle jets, they are as you say, track carbs. As such, they were intended for use with dope (methanol) and can only be tuned for tickover, pickup and full throttle - there is no mid range adjustment. This is fine with dope as it is less critical than petrol regarding mixture strength - also, dirt track machines tended to be used at small throttle openings or flat out - mid range was of little importance. For road use, you may find it better to revert to the 'normal' type of carb with needles - pilot air controls the mixture up to 1/8 throttle, then the slide cutaway takes over until about 3/8 throttle, then the needle and jet control 3/8 to 7/8 throttle, with the main jet controlling 7/8 to full throttle. These are only vague changeover points, as each setting can be influenced by the setting either side of it - and obviously, if too small a main jet is fitted, it wont be possible to correctly make the other settings as the fuel has to pass through the main jet before being contolled by the cutaway or needle. Only the pilot jet has it's own independent internal fuel supply.
  Hope this is of some help,
              Regards,
                         Eddie.

Offline zacgrief

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Re: SW5 Carb settings
« Reply #5 on: 10 Jul 2012 at 07:50 »
Eddie,

Thanks for that and yes you are probably correct about conventional carbs being much better suited for my use. I rode it at the weekend and apart from it was running weak under load which I have to adjust, it ran really well  and pulled very strongly.

Do Amal still stock new carbs and if so whats the model number? I noticed the Bayley-Cole Douglas had a new set of carbs fitted?

Cheers

zac