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· It aint rocket science
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I have a Fluke 88 with smoothing function of display and it is still difficult to follow along with precise readings. All my good old analog dwell and tach meters were used up and long gone, always easy to get RPM readings with the low RPM setting. I have heard good things about the tachs from this company.

Where to start?

Home garage tuning of the carbs is more art than science. When working on carbs the air box will be off doing a visual check of filter and other carb components and I keep it that way through the process. Check of vacuum lines, linkages, accelerator pump etc. You will be listening and looking at engine for smoothness and RPM changes along with exhaust note and carb intake gurgling sounds. When done you will want to be at maximum RPM and smoothness at idle without going rich. A smidge lean is better than a smidge rich for economy and emissions. When the air box is put back on you will be right in the ballpark. Turning screws in is leaner and out richer. Spark plug color will tell you everything about how a cylinder is burning fuel and should be consistent within an engine.

Carburetors are precision metering devices and with a good engine, no vacuum leaks, good compression and good ignition system the mixture screws should all end up within 1/8 of a turn or so when finished. An engine that is running very poorly obviously has other problems and is not ready for a final mixture setting and sync. You got to be aware that someone else may have jacked sync screws out of time with one throttle plate opened to 1200 RPM and another to 700 RPM and others in between and is why a manometer got to be close by. A good engine and carburetors will run well with pilot screws an equal amount of turns out and synced.

I start out lean and work my way up to maximum RPM and smoothness (1/4 turn at a time) on all pilots and then back off to slight lean with a drop in RPM. Final adjustments are 1/8 turn and move as a crew. Cyclo carb clean has served me well over the years in diagnosing carb lean or rich conditions as it burns well and is not foamy like some of the newer cheaper sprays and just a little dribble or slightly more does it. It comes out of the can well atomized. You don't mash on the spray in full bursts.

Start with your initial setting and add a little spray into intake air stream, if engine smooths out and increases RPM turn the screws out and repeat as needed. You will quickly find maximum RPM as a whole and back off from there. Fine tuning of an individual cylinder or finding problem cylinders can be found from the following.


A good quality carb clean spray with straw is a valuable diagnostic aid and I keep a can in the bag.

Bike dies on the road: While cranking spray a little in air intake, if bike wants to fire, fuel problem confirmed.

Vacuum leaks?: Spray a little around suspect area, if idle increases or smooths out found source of leak.

Lean carbs?: Spray a little directly into its individual intake, idle increases or smooths out lean carb confirmed.

Rich carbs?: Spray a little directly into its individual intake, idle decreases
rich carb confirmed within reason.

Quick confirmation of pilot adjustments: Consistent idle (RPM) response when a little spray is introduced to each individual carb intake.

High speed miss?: Spray a little into intake stream, if smooths out and picks up lean condition confirmed.

Avoid overuse around composite parts. (1500 slides for sure) Starting fluid is too volatile and messes things up.

Other bikes can use sync gauge ports for rich or lean checks. Control the uncovering of ports when screw removed idles up it is rich, spray directly in for lean check while sealing area around straw with your fingers.

As always YMMV
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