Tuning by ear

[LoHo]

Hey guys, I need to check my idle jet settings. I know to turn one in until the engine stumbles, then turn it out until the revs kick up, then find a midpoint. Is that correct? I have had a hard time hearing the change with the four carbs. I also know that the tune can be pretty off and still run well enough to ride. Any tips or tricks?

[DAVINCI]

Sure....two tips..

1. Get as close as you can to the mufflers, it;'s easier to hear the change in tone.

2. Hook up an external tach and then you can use two senses, the on-board tach is not very sensitive.

[LoHo]

Yeah, I noticed that the real change is from the pipes. I now have a little popping through the exhaust (more of a thud, really) that was not there before. It runs okay and is rideable, but isn't quite right yet.

[DGXSER]

Popping on decel or while riding under throttle? Decel would be a lean condition, under throttle can be rich.

If you have vacuum gages or sticks, hook them up and watch the vacuum level as you tune the mixture. Tune for the highest vacuum reading, synch the carbs, repeat tuning for highest vacuum, re-synch.

[LoHo]

DG, I have the four gauge vacuum set-up. Are you saying I can run the bike at idle, tune each carb to maximum vacuum, the synch? That sounds easy. I synched them with all of the idle needles out two turns, but it still isn't 100%. The popping was off throttle or low throttle.

[DAVINCI]

DG, I have the four gauge vacuum set-up. Are you saying I can run the bike at idle, tune each carb to maximum vacuum, the synch? That sounds easy. I synched them with all of the idle needles out two turns, but it still isn't 100%. The popping was off throttle or low throttle.

Then you weren't really synching, the way DGXSER described the process is the correct way.

[crazy steve]

Just to clarify, you're trying for the highest equal vacuum reading; the whole point of the sync is to have each carb read the same vacuum as all the others....

[DAVINCI]

Might be confusing, Steve. In the end, you want the carbs to read as close to equal as possible. But during the mixture adjustment you get each carb vacuum to read as high as individually possible, then equal out the vacuum of the whole set with the synch screws. Repeat.

[DGXSER]

Yes, you want to watch the vacuum reading for cylinder no 1, turn its mixture screw to achieve the highest vacuum reading on cylinder no 1. Then repeat for cylinders 2 through 4, tuning each cylinder individually. After all four mixtures screws are at the highest reading, use the synch screws to get all four as close as possible to the same vacuum reading. Now repeat tuning the mixture for one through four, and then repeat the synch.

After two rounds of this, you should be as close as your going to get. I would still watch your plug color now and then and adjust for plug color.

[DAVINCI]

Which brings us full circle and begs the question:

LoHo, if you have the gear, why would you want to 'tune by ear'?

[DGXSER]

It is actually not a commonly known method to tune to highest vacuum.

A lot of folks only read the tech tip on tuning by ear or colortuning. I am not against colortuning, it will get you close. But I like the vacuum method over tuning by ear as I apparently also have a deaf ear for the idle increase.

[DAVINCI]

Well, gee whiz, vacuum tuning is the only way I was ever taught!

[LoHo]

Well, I was never taught any method and have learned by jacking up engines and then trying to fix 'em.

My looking for guidance led to YouTube videos of tuning Jedi who can feel the sweet spot through the force. I would just as soon read a gauge and see it peak and then decline, then tune back to peak, rather than trying to hear a stumble or increased revs.

Speaking of full circle, should I change the adjusters between each carb, the ones used to synch, to about equal before I get max vacuum from each carb, or do I get max vac and then synch it from whatever prior attempted synch I have? The adjusters shouldn't have any effect on an individual carb's max vacuum, right?

[LoHo]

Oh, and to answer DaVinci's question...I wanted to hang with the cool kids who can tune an engine blindfolded and get it to play The Star Spangled Banner up to 4500rpms. Me, I just turn screws and cuss until it is fouled up and barely running, then reset to some baseline and try again...and again....

[DGXSER]

Speaking of full circle, should I change the adjusters between each carb, the ones used to synch, to about equal before I get max vacuum from each carb, or do I get max vac and then synch it from whatever prior attempted synch I have? The adjusters shouldn't have any effect on an individual carb's max vacuum, right?

If the carbs are WAY out of synch, I would synch them up first. If they are pretty close from your last synch, then go for max vacuum. Changing the mixture to achieve max vacuum is going to change the synch also. Which is why you have to synch after each round.