Motorcycle Repair: Gunson Colortune Y or N

Question
Do you suggest using a Gunson Colortune SPARK Plug TESTER?  Have you ever used one & do they work? and what is the correct size for the 305's  Thanks in advance.

Answer
Eric, I actually brought one of those back from the UK in the 1980s, as I recall. You have to be careful with them, as they are kind of fragile. It is an interesting gizmo, but really works better for setting up carbs on Brit cars with dual SU carbs.

Other than the 1961 CB77s which use 10mm plugs, all others take a 12mm short reach spark plug.

You can tune a Super Hawk pretty well by ear and eye.... listening to the sound of the engine at idle, while you make mixture adjustments and by reading the spark plugs carefully.

Unless you have some radical motor in your bike a set of #140 main jets with needle clips at #4 notch and correct ignition timing will keep the CB77s running long and strong for years.

The most accurate way would be to get it dyno-tuned, though...

Bill Silver