Carb Tuning by Ear

[TucmanXJ]

I know a lot of guys swear by the Colortune method but here's a carb tuning method that has worked successfully for me.

Here's a pic of Toucan79 being tuned "by ear." The following assumes you are using all new tune-up parts and that your carbs are clean.

First - warm the engine up to correct operating temperature. I turn the pilot (idle) screws clockwise until I hear each cylinder's firing begin to weaken while also listening to the idle speed & quality. Do NOT turn the idle screw in until the tiny tip touches the seat/orifice hard or it will break off - or jam. This mistake could ruin your day. Then I back out the idle screw about 1.5 to 1.75 turns CC. Normally the idle speed will increase slightly. I work from #1 to #4 slowly and patiently.



At a steady 1,500 to 1,800 rpm I listen for any telltale popping or spitting sounds to ensure each cylinder is firing correctly. After the final throttle chop I listen again at low idle speed for any misfiring and correct it for that cylinder.

After the initial static carb tuning I take the bike for a long ride at mixed speeds and then read each sparkplug for color. So far I haven't had any problems with synching the carbs. Using my "by ear" method there's usually no need.

I realize this tuning method isn't for everyone. With patience and practice one can develop their own "Tuners Touch."

Maybe I'm a bit brave 'cause the bike cost less than the fairing sitting on it. Do not attempt this after consuming your Guiness.

RJ

[randy]

RJ;

What you describe is an idle mixture adjustment, not a synch. For best performance the idle mixture adjustment should be done as part of a proper synch, but doing one and not the other may result in a reduction of performance.

[TucmanXJ]

Homemade Sync

Yes - that's true. One should probably use a Set 'O Sticks to synch all carbs the same.

Guess I've been lucky in this area. If one cylinder seems to get carried away, either working higher or lower, against the others I usually notice the difference in exhaust note and in the engine's low to mid-range behavior. Then its time to break out the screwdriver and go to work making the engine run better, smoother. By this I mean I seek to perfect the machine's "sweet spot."

Example: I designed & built a homemade set of exhaust pipes with HD softail mufflers for my XS850 Special. The bike was tuned exactly "on the pipe." With triple pods and the header style exhaust, it sounded fantastic - more like a Formula One car than a bike. That is, everything was working perfectly: it had a nice, smooth, even idle, with even cylinder firing e.g. it was "in synch." Mind you, this was the third exhaust sytem put on the same bike.

It was, for a stock displacement 850, quite strong on the low end with lots of torque. It ran worlds better than with the factory exhaust system with easier starting and a ton of grunt.

I just sold my custom XS850 to a guy who promptly cut out the baffles thereby ruining the exhaust wave tuning effect. A ride around the block was enough to make me cry ... gone was the patient tuning work in making the bike sing.

By the way ... #1 cyl on the Triple was now popping a bit so I threw an idle adjust on it. Yessir, it coulda also used some mercury stick work (#1 had it's own header tube, #2 & #3 shared a tube) after the cutting but somehow I just had to let it go.

So he's happy with his now loud-er exhaust but he has absolutely no idea what he lost in the process.

Rob

[Stralya]

You built an exhaust system?

Well up until now I was pretty proud of the laminex top coffee table I made (with pre fabricated legs) when I was 11.

Dan
Once proud coffee table builder.

[TucmanXJ]

OK made 1/2 of it ...

A slight exaggeration. The truth will out ... some things work better by experiment; trial and error over pencil & paper design.

I used the stock XS head pipes, welded on two short 1.750" exhaust stubs as collars at ends of the heat shields. The entire rear 1/2 of the stock XS exhaust system was jettisoned.

Then I piped in two HD Softail mufflers 24" long with their center 7/8" dia exh. tubes removed. So now the exh. system was approx. 76" long with 1.50" to 1.750" tubing almost straight thru = high gas flow rate with zero turns.

Inside the hd mufflers oem waffle style on-the-inner-wall baffling helped the exhaust wave pulses with the right amount of resistance and distance.

Due to Tucson's altitude at 2300' the now modified tracts and jetting flowed sufficient air-fuel to supply the XS valves at the intake port. Both intake & exhaust flow pulses were at their ideal frequencies. That's what I meant by tuned "on the pipe."



The 27 yr old bike transformed into an animal - at full throttle it was "hang on and pray." In first and second gear it would absolutely smoke my XJ11.

Coffee tables can become inspiration for space travel, well ok ... space furniture.

RJ

[madmax-im]

Whoa Rob,
What a great looking machine.You have a real stunner there!When i visit Tucson in the coming year i will give you a heads up.BTW would love to see a pik or two of your '79 XS1100 with the Vetter....

[TucmanXJ]

Toucan too

Thanks Madmax-im

The big TOUCAN is getting Robster's custom paint treatment soon.

Color: ALSA MIDNIGHT-BLUE METALLIC PEARL over JET GLOSS BLACK, pro pinstripping in GOLD, covered with multi-layers of Speedclear. This is to be a show-quality MARBLE custom paint job. All cases & aluminum parts will be show polished including the rear drive case. Exhaust pipes will either be rechromed or have a new replacement.

HERE'S a sample of what us so-called "backyard painters" can do ...




Maybe Toucan won't be the fastest kid on the block but he sure will be the best dressed! If funds permit I'll paint TOUCAN's fairing the same color scheme.

RJ aka Da Robster
(da mad painter)