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RB30X

Carb sync tool = bent throttle shafts on triple webbers

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Hooray, my 'Multi Carburettor Syncronising Tool arrived today, so I skip out to my shed like Dorothy along the yellow brick road, fire up the L24 and hello, it doesn't fit so I have to remove the trumpets ;D

 

After trumpets are removed I test each carb with 0% throttle, then again with small throttle opening. I basically got the first carb to flow to 2 then recorded the second carb of each pair. The results aren't to die for.

The figures I'm referring to are the flow incriments on the tool.

 

BcftmkKGrHqEOKkMEq3ObZ6bBK0u0eosw_1.jpg

 

Cylinder  1      2      3      4      5      6

0%        1.4    1.8    1.0    1.8    1.1    1.0

            2.0    2.1    2.0    2.8    2.0    1.7

random  1.9    2.0    0.8    1.6    1.8    1.5

 

The results were inconsistent with the first pair but the two other pairs had similar gaps throughout. Because these are old school Webbers there is no air flow adjustment to compensate these differences, so I guess this means I have at least two bent shafts :'( 

 

Has any one replaced these before. Is it hard. How do shafts get bent in the first place????

 

Thanks

 

 

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Yes, and every time I'd adjust the idle screw for the individual carb I'd open the throttle briefly and let it settle again. But each time I'd adjust one carb (no linkage hooked up) the engine revs would change obviously and effect the other carb readings.

 

Providing I can still get a low rpm idle, does this much difference really matter with low rpm air flow. I'm guessing the shaft itself would only be a bee's dick out anyway so at cruising or high rpm the difference would be minimal.

 

I will perform some more measurements at higher rpm increments to get more readings from the higher end of the scale of the carb sync tool and see how different they are.

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Ok your going to think this is rough but I will tell you anyway

When i was working on alfas we would have the same issue and just give the shafts a tweak

It worked fine and there was never an issue

this was common on brand new alfas so I would just do that if i was you

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If a previous owner has twisted the shafts to correct airflow between cylinders it should be reasonably obvious by either measuring the edgle of the butterfly to carb face or putting a light behind the carb and seeing any difference between butterflies in the two throats. Obviously you will need to take the carbs off to do this.

 

If this is the case, you could try and twist the shafts back to something close to the same, or buy new shafts.

 

I think that if you need to correct flows, and do not have an air bypass, I'd personally be inclined to try small drill holes in the butterflies away rather than twist the shafts. Twisting the shafts will screw with the progression holes, whereas holes through the butterflies (as long as they are away from the progression holes!) wouldn't be as bad? Anyone agree with this?

 

 

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Its such a small amount you need to tweak them

I wouldnt assume they were right from the factory in my experience they arent flash

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