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Reply to "Thunder Ranch build thread"

Ed ....Yes, those are the arms I was talking about. Centerline to centerline should be equal. If they are not, then the pull radius will be different from side to side.  It might be easier to visualize if one side was an inch shorter than the other side. Obviously they would start out from the same position at idle but as the throttle is opened, one side will reach WOT first. (Wide Open Throttle) The carbs would never be in sync all thru the process except at idle. The little pull rods will not compensate for the difference in pull radius.  I hope this helps.

Maybe to prove it to yourself, try setting the throttle, at say, 1500 rpm and get an airflow measurement with your "snail".  At that point adjust the carb linkage so that the snail reads equally on both sides. Then reset the throttle to 2200 rpm and take another snail reading. if everything is perfect, the snail should read higher but equal on both carbs. If not, it's a good guess where the problem is.  Just like Stan says, then it's JB weld and re-drill time to make the centers the same

The same for the lock/set screw that holds those arms to the hex bar. Each time you loosen one and retighten it, you will get a different snail reading.

After screwing around a lot and making some modifications, I was never happy with that linkage system so over the wall it went into my secret parts disposal system.

As I said, I used the Vintage Speed linkage without serious problems plus there is the advantage of being able to simply disconnect the linkage (magnetically) without having to readjust it all again. For perfection the "wheel/cable" system is even better.

Dual carbs are a PIA but when adjusted perfectly, it is a sweet sound to hear !

My guess is that the manufacturing tolerances are not up to par on the hex bar system for starters..............Bruce

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