Having trouble balancing carbs

[gpetrus]

Hi

  I recently cleaned out carbs and replaced o-rings, today tried balancing carbs using two bottle method, carbs 1&2 balanced fine carbs 3&4 also fine, but no matter how much i turn the screw between 2&3  one of the carbs is sucking more than the other, first thought that one of the carbs has a vacum leak somewhere, but doesn't it mean that one of the pairs would not balance too. I also have erratic idle, the needle constantly moves between 1500 and 2000 rpm, if i try to adjust any lower bike stalls, and the engine revs down slowly, but i suspect that might be just sticking throttle cable, and carb clean did not seem to help a flat spot around 5000 rpm

Any ideas?

Thanks

[bullet5]

What are your carb mixture screws set to?  Are the exhaust system, carb jets, and air filter standard?  If not please list what they are.  Have you stripped the carbs down in the past, when was the bike last running good, and what work have you done since then?

Bullet5.

[gpetrus]

everything is standard, the bike was running in a similar manner last summer ie (erratic idle, slow reving down), when i noticed that one of the carbs was leaking fuel into cylinder causing hydrolock, hence got those o-rings, its also my first time stripping carbs, although i followed instructions religiuosly, and to be honest carbs were pretty clean anyway. I set pilot screws 1.7 turns out, I also forgot to add that the bike has a bit of throttle lag when reving from idle to lets say 3000 rpm

[bullet5]

Throttle lag/hesitation is caused by the mixture being too lean.  Back in those mixture screws lightly, then turn them all out 2 1/4 turns.  This should be a good starting point as the bandits were slightly lean in factory trim, so moving the screw out a bit will help richen it up a bit.  One possible reason you bike is hard to balance could be that the mixture screws are not exactly the same number of turns out.  They all need to be set to the same figure to within 1/16 of a turn of each other.

Once you've altered the mixtures, set the idle rate between 1.7k - 2k revs and redo your balancing.

I did mine yesterday and after altering the mixture screws and carb balancing, the revs went up by about 600.  She now idles and picks up very nicely on my "standard" setup (original downpipes with a scorpion can slipped on, with baffle still in place).  Mine's currently set to about 2.5 turns out with this setup, and a that figure is increased further when I have my full Vance & Hines system in place.

All the best,
Bullet5.

[gpetrus]

Thanks for your help, I'll try this, hopefully it helps 

[AlanDog]

Make sure your throttle cable is loose enough not to engage while you do the adjustment. I don't have the factory service manual anymore, but I believe it says to adjust the screw between 4+3, then 3 and 2, then 2 and 1 (ie, right to left looking down on the carbs). I'm not certain, someone correct me if I'm wrong!

I've been able to use the 2-bottle method, but as mentioned, mixture screws (and float height) affect the adjustment.

[bullet5]

Almost, it's 1&2, then 3&4 then the centre screw to balance the two pairs.

If you balance the left pair to the right pair before balancing the right hand pair, then you're going to have to go back to the centre screw afterwards to readjust again as 3&4 will now either be higher or lower than 1&2.

[txbanditrydr]

Remember to use very light pressure on the balancing screws... no more than it takes to engage the slot.  You can affect the synch by simply pushing on the screw without actually rotating it.  Good luck and keep us posted.

[gpetrus]

Will update as soon as I get the chance to work on my bike, (gf taking up to much time) :DD

Thanks again guys!

[gpetrus]

Right, took off carbs, checked float heigt, set the pilot screws to 2.5 turns out, put everything back together, and what a difference, bike seems to have twice the power, idle is much more constant, no more flat spots, also checked the throttle cable, pushed on a throttle lever ( the one on a carb) and it snaps back instantly, but slow revving down was still present, took some starting fluid and sprayed on the rubber linkages from carbs to cylinders, and voila revs went from idle to about 4000. Is it possible that vacuum leak is responsible for revving problem on its own, and how do I go about getting rid of it, I suspect getting new linkages might be a bit of a problem.

Thanks