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Vacuume Guages

Discussion in 'Technical and Troubleshooting Torque' started by nicka, Jul 11, 2007.

  1. Can anyone tell me what range a set of vacuum guages need to be for carby tuning.
    I am able to get 4 new guages 0-30"hg cheap but i am unsure of what range they need to be for tuning.

  2. they'll do.....

    (can you get me a set as well? :wink: )
  3. Thanks Iffracem

    I just did a search also and the proper tuning guages are 76 cmhg which equals 30"hg so i'm in luck. :grin:

    And sorry they are the last 4 :p
  4. A two gauge set will tune ANY multi carb engine.
    You set one cylinder up as a master and reference teh rest off that one, so it's just a matter of moving a vacuum line each time you set one carb. Adds, oh, one extra minute to teh entire procedure.
    And if you're frugal, a two gauge set is usually just over half the price of a four gauge set, plus it's smaller and easier to store away.

    Regards, Andrew.
  5. get mercury gauges for balancing... dial gauges tend to go out of calibration.. mercury gauges dont. They are made for balancing quad trottle bodies. It much harder to get accurate balancing on dials as the 4 needls spin rather than rise.

    Only downside is transporting them....

    pretty cheap... saw PS city selling them under @200. was around 180 i think, and they come with a set of adapters to suit hondas.

    however any vacum gauge designed for manifold readings will be ok. you should be fine with them. gl hf dd
  6. careful with mercury manometers... even an old clapped out vf1000 has the ability to suck the mercury out of them if you're not careful...

    eh Techno :-w
  7. if you were to let that happen you shouldn't be using them...
  8. really........

    even tho the correct restrictors were in place and the motor not revved above 1,200, the recommended revs for balancing, there will always be the possibility of the mercury being drawn out of the tube.
    Used to tune two stroke GM diesels with the mercury manometers without too much trouble, but sometimes, things don't work to plan, no matter the planning, setup and care. Which is why, in the context of this thread, a set of gauges would be far better, and safer to use than a mercury manometer, even without discussing the dangers of using and storing mercury, esp in a home environment where pets and kids could be around.

    That was my point, gauges are the better option, they can be easily "damped" to stop the "bouncing" caused by cylinder fluctuations, easier to store and transport., and unless launched at ballistic speeds, I doubt they'll kill you, unlike mercury
  9. Thanks for the tips.
    I made a set a while ago using water tubes but i sucked the water in a couple of times so i shure would do some damage with mercury.
    The water tubes worked but they were dificult to keep steady using restrictors but i have some needle valves to conect to the guages this time so all should be good for steadiness.
    I'll post a pic when i get them and have them set up.
  10. Perhaps I havn't used mercury gauges enough. I only run one restrictor on the breather in my personal set, don't have a problem. Needle gauges havn't impressed me as yet. opinions like arseholes ey...
  11. I'm back with some working gauges


    I have connected them up and they work great but trying to tune here's what i am finding.
    Trying to tune with the gauges i can get them all spot on but it seems not right as i seem to be able to get the engine sounding a lot smoother by adjusting the screw and listening by ear.
    Also when i drop the revs back down to idle the gauges are all over the place but resume back spot on when the revs are back up.
    When i have done it by the gauges i have clutch rattle as i have always had but i can remove this rattle by doing it by ear with the smoothness of the motor running.
    Do i go with the guages or do i do it by ear.

    The gauges are calibrated as i checked them myself with a pressure calibrator so i know they are spot on.

    I'll post some pics later as i wanted to put some pics together with some video footage also with the engine sounding better after it was tuned.


  12. I recently synchronised the carbs on my zzr600 with a $50 guage from Bursons. When connected directly to a carb the needle was all over the place. This was fixed by using a large jam jar as a vacuum tank between the guage and the carb. All needle movement was eliminated leaving a steady reading.

    Hope this helps
  13. Before you sync with anything, everything else has to be OK.

    That is, plugs clean and correctly gapped, valve clearances OK, fuel bowl float levels set correctly, all the jets, ports etc clean, no air leaks, anywhere (mating surfaces, gaskets, butterfly shafts etc) The idle air bleed screws must be correctly set, and all as close to identically set as is possible. The linkages and shafts must be free to rotate, no binding at all.

    The engine must be at operating temp, and the revs at the correct speed. Any one of these not done, and the results are what you're seeing.

    I'd go back and recheck everything, esp float level and air bleeds. might pay to have a desk fan blowing air onto the engine to simulate airflow as well, stop it from overheating.

    Then it's just practice... practice .. practice.

    You're ability to pick up teh problem "by ear" is good, IMHO shows you have the empathy and "knack", but don't second guess the tools, they will be far more accurate, all else being OK.
  14. One thing I have not had the skill/opportunity to do.
    So when would you be required to balance the carbies? and what parts of the carbie would you be modifying to alter air flow rates? (considering 99% of slides are vacuum operated)
  15. The slides are vacuum operated, the throttle blades are not. They both control airflow, but by synchronising carbs at idle, you are setting the asame airflow relative to all other carbs. What you are adjusting is the screws that set the idle position of the throttle blades on some carbs, or the grub screws and idle speed screws on other carb setups.
    Here's one I prepared earlier:

    Regards, Andrew.