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Carby Balance? Huh?

Discussion in 'Technical and Troubleshooting Torque' started by Pommy, Feb 8, 2008.

  1. I have a GPZ600R and was given a mercury thingy which has to be kept upright - is this piece of equipment useful/expensive/worth keeping?

    He told me it was to balance the carbs - ?


  2. Worth keeping and useful yes. I'm not sure about price, maybe $100+ new.
  3. Since you don't know what it is, I'll take it!
  4. Much better/simpler than gauges. A bastard to transport and a toxic bomb in your garage, but they certainly work.
  5. Ok, well that's cleared up what it's for - it came with no instructions...

    What do I do with it?


  6. Find someone local to teach you how to use it.
  7. Are you mechanically minded?
  8. The local bike mechanic is tied up for 3 weeks - can't even book in with him.

    The only other choice was dealer - so I'm learning myself.

    Most definately.



  9. Dansmc is a world famous internet resource for DIY bike maintenance. Have fun.
  10. Cheers Rob.

    Reading the info on how to do it outlines a problem I have - it sounds just like it, but...I think I'll leave it to the mechanic to decide as it may not be.

    Oh - the problem.. lol.. when you throttle back from idle fast it dies - if you hold it over 2K and then throttle back it's fine.. responsive as it should be...

  11. Okay...

    Hang the balancer in a convenient location so the tubes can reach the carbies, and so it hangs or stands vertically: I suspend mine from the handlebar using wire. Now, find the carb balance ports: they will be small screws on the inlet ports, probably between the carbs and cylinder head. You will need adaptors to screw into these: nothing more than short brass tubes with a thread and locknut on them. Remove the port blanking screws, screw in your adaptor tubes, push the balancer's clear plastic tubes over the ports. The other end of these tubes attach to the top of the balancer columns. Make sure they are in order.

    You should have the reservoir of the balancer almost full of mercury, and the tubes pushed deep down into the reservoir.

    Now, start your engine. The vacuum in the ports will draw mercury up the columns. Don't rev the bike hard, or it will suck the mercury out the top of the columns and into the motor. A fast idle speed is about right, around 1500-2000rpm. Adjust the idle speed up, then re-adjust it when you're finished.

    On your carbies will be screws to adjust the balance: they work like idle speed adjusting screws. They will typically be small screws between the carbs, so three screws on a 4-cylinder bike. The left screw will adjust carbies 1 relative to 2, and right screw will adjust 3 and 4, and the centre screw will adjust 1/2, and 3/4. Play around with them until the mercury columns are even.

    Now disconnect everything and enjoy your smooth-running bike. Sometimes, older bikes especially just won't run evenly. This can be air leaks, uneven wear/compression, or even a weak spark. But at least you'll know and you can get the bike running as well as possible.

    One final note: I use a spare fuel tank with a long hose so I can run the bike and have easy access to the carbies. Store the baslance well away from interference or harm, and keep mercury away from the environment: the balancer had enough to kill a small town.
  12. Cheers mate!

    Very impressed.

    I'm off work tomorrow so I'll have a go at it - i'll take a swig of the mercury tonight to build my confidence up...

    Just kidding - mercury should only be injected.

    Wish me luck!

  13. Another tip for mercury manometers.

    Store upright in a cool place, but not in your house, where you spend most of your time - mercury will evapourate, albeit very slowly, Cap any open ends. You don't want to inhale the vapours.

    Unlikely to kill you, but causes irreparable nerve damage - see minimata disease. - extreme exposure is not good.
  14. Oh, and i've also read that if you accidently suck the mercury out of the manometer and into the engine it will damage/destroy it (the engine, that is!). I've never used one, but i can't imagine an engine full of mercury could be a good thing :grin:
  15. Actually the best trick is to remove the mercury with a pipette and store it in a small glass jar firmly closed when you're not using the gauges, that way it doesn't disappear. Also, make sure it NEVER gets in contact with your skin: as it is a heavy metal it will be absorbed through your skin and stay in your organism. And it is not good at all for you, I can tell you that :LOL:
  16. I had a Morgan Carbtune II and used it to balance the carbs on my BMW R75/7. I thought the Carbtune worked just OK. It seemed a little bouncy, but that may have been that it wasn't damped correctly.

    I always thought that a mercury type balancer might be smoother and more accurate (albeit much more nasty to your health).

    Anyone know where to get a mercury balancer in Oz? Preferably the Melbourne area.

    I've also made my own balancer as others have suggested on the forums. i.e. a length of clear plastic tubing taped to a large ruler and filled with transmission fluid. In the end, I thought it worked better than the Carbtune.

  17. I've got one carbie hanging out each side. Assuming they are the same weight, does this mean they will automatically balance? :LOL:
  18. Surgery might help...