intake pressures as measured form the 5mm port

Rick said:

what should the pressure of each side measure, not the differential pressure, but the gauge vaccuum pressure. Clymer's indicates 40mmHG or less to be in sync...but I want to know how much vaccuum I could expect if I just measured one side alone.

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Sort of off the wall, but how many forum members remember vacuum windshield wipers??

That tells a lot about our ages. I drove several cars with vacuum wipers. I am also an old

***t.

RAGBrian said:

Back on topic...what was the original question? Can you provide more from Clymer? A lot of us have the Honda specific service manual, so if you have that and can reference the chapter & page, we can all look together.

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I just wanted to find out what Vaccuum pressure I could expect to find if I were to measure one side alone. I understand that sync'ing the carbs is independent of the magnitude at each port but a measure or comparison of the differential pressure between the two cylinders.



Clymer's pg41 step 9. indicates that "If the difference in gauge readings is 40mmHG or less between the 2 cylinders, the carburetors are considered synchronized." That delta seems high, and just wondered what the Pressure range was and what the decay was as the intakes were opened.



I wondered if there was a base line vaccuum pressure that I can confirm I am starting with on each side, or if there was a factory value maybe? I have access to some really nice hand-held digital manometers with damping features and the like and want to have the instrumentation spanned correctly for DP and would also like to check the vacuum for each side.

Absolute vacuum readings vary as to the ambient air pressure, the camshaft specs, and the general condition of the engine. There can never be a "baseline" number. In the old days where carbs had adjustable idle screws, it was possible to maximize the vacuum numbers by going back and forth between the idle mixture and the throttle stop. Once you got the highest idle vacuum reading, it was good.

When I sync my bike the reading on the vac gauge was around 8 inchs of vac on each cyl @ idle .I get both cyls pretty much exactly the same when syncing & no more than .5 inchs difference.As mentioned prev altitude & temp will vary readings but thats the numbers I get.I think this is what you are asking.

perfect! thanks for all of the feedback guys;

As a note on synchronizing, when doing any adjustment to any carb, remember to open and close the throttle after



each adjustment and then read the guage after it settles to idle. This will result in a more accurate reading.

Old Okie said:

Sort of off the wall, but how many forum members remember vacuum windshield wipers??

That tells a lot about our ages. I drove several cars with vacuum wipers. I am also an old

***t.

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Oh yeah. My first car was a bit older than me, a '56 Ford F150 panel wagon.



Cheers!