Carb balancing?

[beemer]

Can i get some advice on how to balance my carbs on my R65LS,thanks,J.

[Justin B.]

It's kind of a black-art and hard to describe just in text.  Basically the bike needs to be at operating temp (15-20 minute ride), correct free-play set on the cables, set curb idle speed and adjust idle mixture screws, touch-up idle speed, then you will adjust one of the throttle cables slightly so both carbs throttle plates start opening at the same exact time when the throttle is twisted.

You might want to do a search on this board as I think it's been discussed in the past.

[nhmaf]

While it is possible for some folks to get them fairly close just by "ear", I think that it also presumes that the carbs are both clean & functioning properly, with jet needles set at proper position, idle screws adjusted, etc. as Justin describes.  If it they aren't, then it becomes even more important that one use some sort of gauge set to balance them as
severe discrepancies become visually apparent.   You could use a Twinmax balancer (a simple differential pressure meter) or use mercury gauges, or build a set of your own gauges using ATF fluid, or use a metal slide (rotameter) based gauges set like I do (CarbTune).

you do have to make sure that your valves are already adjusted properly (do them when engine is stone cold) and have a basic feeling that your carbs are basically working properly (no torn gaskets or diaphragms, stuck needles/floats, plugged idle jets, etc) before you start.  Also good idea to know that your ignition advance is working properly.
Problems in these other areas can work against you to severely complicate the carb balancing or make the engine behave in a manner inappropriate to your carb balancing adjustments, causing alot of confusion and frustration.

IF you go to the Bing website:
http://www.bingcarburetor.com/
you can get their carb manual for $10, which has a process described in it for tuning/balancing carbs.   They also sell a DVD video of many carb maintenance and adjustment procedures.

[Justin B.]

Uh, yeah, what he said...  :-?

[beemer]

Thanks for you help,i will look into it,cheers,J.

[not-so-fast-ed]

Semper Gumby spent about 20 minutes on my carbs with his balancing meter, and wow what a difference!

 

Ed

[steve hawkins]

I have what is often described as the $5 carb balancer, which works very well.

It is a long flexible transparent tube with the centre part fixed to a plank of wood in a U shape (like a barometer), you can put some graduations on the plank if you are feeling techie.  The u tube has some fork oil in it at the bottom, and you connect either end of the of the flexible pipe to your carbs - underneath you will find the inlet take off point with a screw in them.

This system works a treat.  Like mentioned above.  Make sure all other aspects of tuning are set, valves, advance etc and with a warm engine, set you idle using the balancer, followed by the throttle take up.  

There must be slack in the throttle cables at idle or you will get the dreaded 'Hanging idle', where the engine will not return quickly to idle when you shut the throttle off.

The technique with this system is to blip the throttle to start with and make sure the oil does not rush up one side of the tube, adjust the cable adjuster on one of the carbs accordingly, when you are close to perfect, i.e. same pressure on both ends of the tube, you will be able to open the throttle for a longer period to fine tune it.  If you wack open the throttle for a prolonged period straight away, it is likely that one of the carbs will suck up all your oil in the balancer.

Be aware that you do not adjust one cable too tight, as you will get the hanging idle problem.

10 mins - normally.

Steve H

[beemer]

I have what is often described as the $5 carb balancer, which works very well.

It is a long flexible transparent tube with the centre part fixed to a plank of wood in a U shape (like a barometer), you can put some graduations on the plank if you are feeling techie.  The u tube has some fork oil in it at the bottom, and you connect either end of the of the flexible pipe to your carbs - underneath you will find the inlet take off point with a screw in them.

This system works a treat.  Like mentioned above.  Make sure all other aspects of tuning are set, valves, advance etc and with a warm engine, set you idle using the balancer, followed by the throttle take up.  

There must be slack in the throttle cables at idle or you will get the dreaded 'Hanging idle', where the engine will not return quickly to idle when you shut the throttle off.

The technique with this system is to blip the throttle to start with and make sure the oil does not rush up one side of the tube, adjust the cable adjuster on one of the carbs accordingly, when you are close to perfect, i.e. same pressure on both ends of the tube, you will be able to open the throttle for a longer period to fine tune it.  If you wack open the throttle for a prolonged period straight away, it is likely that one of the carbs will suck up all your oil in the balancer.

Be aware that you do not adjust one cable too tight, as you will get the hanging idle problem.

10 mins - normally.

Steve H

Sounds a great idea to me!!thanks,J.

[steve hawkins]

Here is a link to the Airheads article I blagged it from:

http://www.airheads.org/content/view/183/98/

Cheers

Steve

[thrang]

You can get them roughly balanced by ear, but its a dam sight easier to spend a few bob on a set of M&P gauges and balance them up properly. And the cost of the gauge works out negligable in the long run as you'll prob pick up a mile or two on the gallon if your carbs are sorted.

[MrRiden]

I like using the 5$ manometer as much as I like using an electronic tuner for my guitars. I just don't have the ear for either without help. Heres a variation on the $5 balancer that looks interesting,
rich

[Justin B.]

Well, first time I've seen that mutation...

[beemer]

I like using the 5$ manometer as much as I like using an electronic tuner for my guitars. I just don't have the ear for either without help. Heres a variation on the $5 balancer that looks interesting,
rich

It would be good filled with red wine!!!at least there would be an excuse for sucking it out afterwards!!!(but don't go for a test ride till the next day!)very interesting idea,cheers(hick!!)J.

[mikethebike]

I use a Morgan Carbtune.  I bought it for my CB750K (4 cyl) and it made that job so easy. Mike