Bonneville America Forums Forums Technical Forums General Tech Carb balancing??

I have been reading some of the post about the cheap carb balancing tools to make at home. Last year I changed my set up, and saw it was recommended to balance your carbs after making mods. Could somebody explain to me the mechanics of what's up with the balancing. Like what makes them out of balance? What difference does it make/symptoms the bike shows? And if they are out of balance after testing then what the heck do I do?
Thanks-Brett

You want to make sure that the butterflys are opening up together for obvious reasons. The only way to check is with a vacuum gauge or manometer. I hook up my vacuum gauges to the engine, run it at 1500 rpm and see if there is a difference in readings. If there is I adjust the adjustment screw situated between the carbs until the vacuum is the same. Hard to see the screw. Once I do that, I adjust the mixture screws (one in each carb) until the engine idles it's best. I then check the balance and readjust if necessary.

If the balance is out a lot, this will smooth out engine vibrations around 3500, cause a subtle increase in power and balance the load equally between 2 cylinders instead of unequally between the 2.

This is the Carb Balancer I purchased. Got mine for $40 US last year.

I used to have the CarbTuner II, it worked very well. Lent it to someone and never came back... now it's lost... darn!

So, I made this to balance my carbs at home... very simple, very cheap and easy enough!

http://www.youtube.com/watch?v=0nKaGEMLZjs

I use one of these.
http://cgi.ebay.com/ebaymotors/Morgan-Ca...=item3a5abab2da

Not "cheap", but worth it to me. Well made and extremely easy to use!

I've got a Twin Max. Works fine. Not the MOST technical solution, but good enough for me.

You should check the balance all over the RPM range. It should stay pretty close all the way up and down.

I have always used a home made version similar to the one Perceval posted but not as complicated. I used zip ties and a yard stick. I added a small ball valve at the bottom of the loop in case it is far enough out to suck fluid into the engine. Hook it up, start the engine, slowly open the ball valve. If it is way out you can close the ball valve,adjust a little and try and open it again. I also use 2 stroke oil in it so if any does get sucked in the engine it will just burn and not hurt anything. It is also a good idea to have a big fan or 2 blowing on the engine while working too keep it cool.

Thanks guys. So let's say I do find them out of balance. How do Ifix that?

There is a screw between the carbs near where the cables connect that you turn to adjust them.That one screw is the way you adjust both since all you are doing is making sure they both open the same amount at the same time.

Very cool. Thanks, Ian. I think I'll make this a little project for me one day when I'm bored soon.

It takes very little movement of that screw to make a major change, measure it in very, very small movements...

Greg, I have the Exact same gauges but Instead of 4, I've got a pair of them on a metal plate size by side. They've worked really well and for the price I've never regretted the purchase. To aleviate the needles pulsing though ( I suspect yours are the same ) mine have inline thumb screws that adjust and lessen the higher than needed vacuum amount thereby preventing any pulsing.

Btw, I originally bought the 4 x murcury gauge but preferred the needle type gauges. Certainly both types seem to work equally as well but I just liked the idea of the needle type.

BTW, Great pics Moe. Those should be entered in the Tech Vault under "Carb Balancing screw location".