Re: Adjustment of carbs on 65 BJ*
Hello Patrick, I believe you are right about the book saying to basically block up the piston on the carb you are not TESTing to get a good read on the one you are lifting with the pin. But also, I do not believe the book will tell you to loosen the connecting linkage again, after you have made sure the throttles are closed. Although it might direct you to leave the throttles separated until you are finished with each carb adjustment. But you see if you blip the throttle to see how the engine is responding to your work the throttles must be tied together. Blocking up the piston on the carb that you are not adjusting is illregardless of the fact that you must ensure that the throttle plates are closed or you will be feeding too much fuel to the engine via the carb that you are not adjusting and you won't be able tell what is going on. I and my fellow British car nuts around here do not bother to block up the other piston (on HD8 carbs) and have had good results for about 30 years. But that is why I told Bob to reread the book again in hopes that with what I said will help to make the methodlogy alittle clearer.
As a last point, you will see that with the HD8 carbs, the syncronizing the air flow with a tube or hose or unisyc is moot since the throttle plates must stay closed. That is why HD8 carbs are so much easier to adjust that previous SUs. With the previous SUs, you must separate the linkages and set the air volume thru each carb to match by adjusting the position of the throttles and listening or measuring the air flow. Then with balanced air flow you go ahead and adjust the fuel richness by adjusting the position of the jets. With HD8 carbs, if they are not flowing the same amount of air you would have to have a major physical malady with one carb or the other. With the throttle plates closed they have to be flowing the same amount of air. If you look at the carb schematics you will see that the passage that flows FUEL/AIR MIXTURE around (bypassing) the throttle plates IS the "MIXTURE", it is drawn off part of the carb structure after the main jet so it is really a "MIXTURE". All the slow run screw does is reduces its volume or increases it. With the previous carbs, there is no bypass idle circuit (slow run) around the throttle plates. On previous SUs, you would set the throttle plate open alittle, thus allowing air into the engine and then with the main jet situated in the main vortex of the carb you adjust the jet to give it fuel. Anyway i am not an engineer so my symantics may be confusing. I'm sorry for that. But it works for me.