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Old 02 January 2013, 10:08   #1
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Carb Balancing ...

Most of the engines I've ever fiddled with have only had one carb - so simple stuff,

But the Yams of course have three...

Just to clarify when you 'balance' them - is it just a question of getting the throttle butterflys set to the correct angle/opening to allow each carb the same 'suck' as its mates ? (Allowing for the one that has a 'hole' in it - Edit - think thats the choke one anyhow - Maybe to allow one cylinder to start easier ? I've no idea !)

Current thinking is it cant be much else ? Mixture screws to be set at 1.5 turns out on each and idle speed screw set of the middle carb adjuster ?

Pete
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Old 02 January 2013, 10:52   #2
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Most engines have fixed throttle rods, theoretically all carbs must have same mixture screws turns, if wanting state of the art accuracy, connect one vacuum gauge to each cylinder manifold to adjust all 3 carb mixtures same, finally adjust idle rpm screw to factory working parameters. There are vacuum gauges in digital versions on the market with led lights readings for banks of 3-6-8 individual cylinders.

Happy Boating
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Old 02 January 2013, 13:56   #3
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Quote:
Originally Posted by Locozodiac View Post
..... connect one vacuum gauge to each cylinder manifold to adjust all 3 carb mixtures same, ....
Erm, unless something has changed, the balance is achieved by adjusting the throttle stop screws individually then locking the throttle spindles together.

For info, you can do a pretty good job by sticking one end of a tube into yer lug and placing the other end at the carb mouth. Listen for the hiss frequency to be the same.
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Old 02 January 2013, 14:30   #4
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Simple enough with one of these I swear by it
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Old 02 January 2013, 14:55   #5
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Simple enough with one of these I swear by it
Handy - but at 35 ish I'd probably only use it once every four years....

Wonder if I could borrow one ..from someone ...hmmm

But basically am I right ? you are just checking and correcting the suck on each carb by tweaking the butterfly position ?
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Old 02 January 2013, 15:00   #6
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use a rubber tube and get the suck noise to be the same
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Old 02 January 2013, 16:27   #7
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Gunson G4053 Carbalancer

Internal combustion engines use a mixture of air and petrol to generate their power. The performance therefore is influenced by the air flowing into it and the petrol that is metered out by the carburettor. Unless the air flow in Twin or Multiple carburettors is correctly set, the correct mixture adjustment is unlikely to be achieved. Suitable for use on SU, Solex, Auto-Lite (Formoco) Stromberg, Weber and Zenith and can be adjusted to fit most carburettors including side-draught, down-draught with air intakes (Venurei) from 25mm to 67mm (1”-2”) diameter
Easy read scale indicates the air flow and allows
Provides smoother and better acceleration
Carbalancer can be adjusted to fit most carburettor
Easy to follow instructions
14.00
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Old 02 January 2013, 16:28   #8
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Cheap enuff?
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Old 02 January 2013, 16:29   #9
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I posted on this topic earlier this year on a yamaha forum and someone responded with a description and shots of a home made vacuum gauge. In the end I got a mate who's in to four carb race cars to lend me his. It's a very easy job, but stripping, cleaning and replacing gaskets on four carbs took about eight hours. on my f100 you just balance the top three to whatever output the bottom one gives. I can't begin to tell you what difference it made to the boats performance.

The home made balancer used rubber tube nailed to a piece of wood in a u shape with water in. will try and dig it out for you
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Old 02 January 2013, 16:30   #10
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well it's only half of 35,
I reckon a tube at 0.75p is better.
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