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Syncing Carbs

Discussion in 'Technical and Troubleshooting Torque' started by momo, Oct 19, 2007.

  1. I have been attempting to balance the carbs of my ZXR250C using a Carbtune Pro, and I have not had any success. The problem is that adjusting the screws has no predictable effect upon the vacuum levels, and even if, by chance, I manage to get all four aligned, it is impossible to keep them aligned. If I leave the bike idling, touch the throttle, or stop the engine and restart it, the levels will move substantially out of alignment again.

    The procedure I followed was to:

    Splice the dampers into the hoses;
    Attach the hoses to the carbs;
    Start the bike and let it warm-up for five minutes;
    Adjust the screws for cylinders 1/2 and 3/4, then the middle screw; and
    Open the throttle slightly to see whether adjustments were 'stable'.

    It doesn't seem to be too complex a thing to do - am I completely missing something :?
  2. i still haven't attempted to balance my carbs, but i believe you are ment to check the readings while the bike is still a little cold, when the bike heats up the readings go all wacky.
  3. Wacky readings could mean your carbs are simply wearing out, and not maintaining a consistent behaviour at idle. EG worn slides, holed diaphragms, etc. Get the settings as close as you can, and then just ride the bike. If it still runs poorly, get the carbs checked by a mechanic or knowledgeable mate (not just one who thinks he is knowledgeable :grin: ).
  4. The carbs seem to be in fair condition. I took them out, thoroughly cleaned them, and had them serviced. The gaskets were replaced, the slides were in good condition, and there was no apparent damage to the diaphragms.

    I will try it one last time next weekend. I hope the same thing doesn't happen as last time - I ended up with a mixture rich enough that every time I rolled off the throttle, it backfired constantly :LOL:
  5. Carb synchro should NOT adjust your mixture at all. Mixture is taken care of by the mixture screws under the bottom of the carbs.

    If in doubt, you can do a basic synch of the carbs by taking them off and using your thinnest feeler gauge on the butterflies (you need a gentle sensitive touch to get it perfect this way). At the same time, re-set your mixture screws to the setting recommended in the manual. Make sure your idle speed screw is backed all the way off before you do this, and when you reassemble and start the bike you can re-set the idle.
  6. hmm ... is it possible I was adjusting the wrong screws? :p hehe I don't think I was (there were only 3), but I definitely screwed something up when I tried to sync it because it was backfiring a lot afterwards. Ah well - I'll have a better look next weekend. The bike is in a shop at the moment so there isn't much I can do at the moment.
  7. at least you tried(i know plenty of people that @#$@ out), hopefully the mechs can explain wat you did wrong & you can do a better job of it next time. I reacon the best thing about having a bike is working on it :D