Balancing carbs

[Arbman Al]

Trying to retune and balance the carbs after a rebuild, and can't get them quite right.

Tickover is a little bit up and down, checked all the breathers and remade one of them so a better fit.
When using a syncro balancer the reading goes right up to almost the top, is there a setting where they are supposed to be, or doesn't it matter as long as they read the same?

Cheers....Al

[milothedog]

Trying to retune and balance the carbs after a rebuild, and can't get them quite right.

Tickover is a little bit up and down, checked all the breathers and remade one of them so a better fit.
When using a syncro balancer the reading goes right up to almost the top, is there a setting where they are supposed to be, or doesn't it matter as long as they read the same?

Cheers....Al

Hi Al,

It doesn't matter what the reading is as long as they are the same but are you doing it with the link between them removed!

Ian.

[Arbman Al]

Hi Al,

It doesn't matter what the reading is as long as they are the same but are you doing it with the link between them removed!

Ian.

Yes Ian, I am.
Just checked ignition timing and it won't hold steady with a timing light on it, keeps bouncing around.

Is it all related do you think?

Al

[milothedog]

Could be if it's hunting on tick over, if you have electronic ignition there's no reason really why it should need adjusting. have you got any fuel or vapour coming out of the carb overflows (needle valves leaking) that would upset the tick over.

Ian.

[Stagdad]

Al is this with the new ignition fitted?

Steve

[Arbman Al]

I've rebuilt the carbs, replacing butterflies, spindles and seals (rubber in old seals was rock hard and crumbled away when I prised them out). New main jets and needle valves in float chamber. The main jets I have set at 1.5mm down as did Steve Stagdad.

No petrol overflowing, but thinking about it the petrol is about 6months old so will put some fresh in tomorrow.

I'll give Steve a call to see how his is behaving.

Cheers....Al

[whitev8stag]

Could be if it's hunting on tick over, if you have electronic ignition there's no reason really why it should need adjusting. have you got any fuel or vapour coming out of the carb overflows (needle valves leaking) that would upset the tick over.

Ian.

leaking needle valves were my problem, same sort of problems as well.

Ben

[Arbman Al]

Al is this with the new ignition fitted?

Steve

Yes Steve.
Car starts ok, and is not too bad on a run, feels a bit under powered to what it was though. Tweaked the mixture up a quarter turn tonight and my old gunson co2 meter is showing about 4.0 ish.
I'm working tomorrow so will put some fresh petrol in when I get home, and go for a bit of a run - to Bracknell even!!

Cheers...Al

[V Mad]

Al, the ignition timing should be stable unless the engine is revving much too high. Are you sure the ignition unit is installed and wired in correctly?

[Arbman Al]

Al, the ignition timing should be stable unless the engine is revving much too high. Are you sure the ignition unit is installed and wired in correctly?

Hi Chris
Tickover is 650-700.
The ignition module only has two wires to fit. One to 12v on inertia switch, and the other to coil negative.
It is an LD Parts module that fits inside the dissy.
Cheers......Al

[Ian Durrant]

Yes Ian, I am.
Just checked ignition timing and it won't hold steady with a timing light on it, keeps bouncing around.

Is it all related do you think?

Al

Hi Al,

I thought mine was erratic but it turned out the pickup was just picking up pulses erratically from a neighbouring plug lead. I then found out my sensitivity adjuster was broken on the gun, once fixed I was able to turn the sensitivity down and the light showed a stable timing mark.

I would guess this cross firing is likely to be worse with a high power electronic ignition.

Hope that helps

[V Mad]

That sounds ok, so long as the elect ingition gets a proper 12v not a ballasted 12v. I wonder if your dissy advance mechanism is palying up?

[Arbman Al]

On the base of the air valves there are two holes. I read somewhere that they should face a certain way but can't remember which.

Anyone know, and would it make a difference? What do they do?

Cheers...Al

[Arbman Al]

On the base of the air valves there are two holes. I read somewhere that they should face a certain way but can't remember which.

Anyone know, and would it make a difference? What do they do?

Cheers...Al

[milothedog]

On the base of the air valves there are two holes. I read somewhere that they should face a certain way but can't remember which.

Anyone know, and would it make a difference? What do they do?

Cheers...Al

Al, IIRC the holes should be facing the air intake, don't the little lug's on the diaphragms ensure this! the bias of the needle should also be to the 2 holes. as regards the effect, I can't see that it would affect the tick over and would only hinder the lifting of the air valves when the throttle is opened. have you got the bypass screws both closed! they should be if there not.

Ian.