Zen and the Art of Carb Balancing

[kiroh]

Got the cheapo carb balancing gauges from Busters and after finding the balance screw (thanks YEN_POWELL for the brilliant picture) got them balanced in no time. The engine runs much smoother and horrible vibration at low revs is gone.

But a few things didn't seem quite right -

Firstly - I had to turn the screw nearly 3/4 of a turn. From what I've read before in this forum the movement should be very slight. Could this be a sticky choke cable?

And also - can anyone tell me what readings should I get on idle and when reving up?



When on idle I got about 11 inches of pressure (between the two red zones), but after slightly revving the engine the pressure dropped to the red zone which reads "Late valve timing or leak at intake manfold or heat riser", then settled on 11 again. Is this expected?

Thanks

[djadams]

Yes it's expected - when you open the throttle, the pressure rises (the gauge vacuum "drops") until in an ideal system with the throttle wide open, the pressure would be the same as atmospheric (i.e. gauge vaccum of zero).

If you blip the throttle, the gauge vacuum should fall as the throttle is opened, then rise to a "high" reading as the throttle is shut at a higher engine speed, and then settle at the same level as normal when the engine is settled at idle with the throttle shut.

The comments on the gauges only apply with the throttle shut and the engine idling at steady state.

[piguglyshandydrinker]

The specific readings of the gauges are of no relevance, getting both readings the same is what matters.

It can be very difficult to get the cheaper gauges calibrated, fit a 'y' piece & calibrate with them both running off the same carb.

I had the ones shown & found them crap, couldn't even to give consistent readings on the same carb.....

Phil

[Cie]

Well if those gauges are crap, any idea where to get a decent one from?

[djadams]

I have a "Carbtune II" which I bought years ago. Always been chuffed with it.

Expensive but recommended.

[YEN_POWELL]

I have a "Carbtune II" which I bought years ago. Always been chuffed with it.

Expensive but recommended.

I have a carbtune 1 (mercury ooh) which I bought even yearsier ago and I also am chuffed with it. Dials are for wimps!

[Reevie]

I'm fuggin pleased you found it easy to adjust the balance screw-----what a bastid of a job ---i reckon MR Honda had an off day when he decided to put it there.

But i have to say she does run sweeter ---especially with the stage 2 dyno jets fitted

[Reevie]

I have a carbtune 1 (mercury ooh) which I bought even yearsier ago and I also am chuffed with it. Dials are for wimps!

yep thats what i balanced mine with ---use the little black dibs to blank off the mercury tubes you dont use and away ya go

[YEN_POWELL]

yep thats what i balanced mine with ---use the little black dibs to blank off the mercury tubes you dont use and away ya go

The only thing is, they don't travel very well. If I take them anywhere and they get laid down I have to take the little syringe to remove airbubbles before using them.

[piguglyshandydrinker]

Morgan Carbtune are OK, the best I have seen are the Davida dial guages - top qualitypiece of kit.

You can make them from a piece of clear pipe shaped into a 'U' shape & taped onto a 4 foot stick and part filled with water/oil etc. Never tried it but sounds logical.
I believe kits can be purchased from ebay cheaply too.

Phil