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Motorcycle Repair/Gunson Colortune Y or N


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.

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

Motorcycle Repair

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Bill Silver


Need help with vintage Hondas from the 1960s? I am an expert with 250-305cc bikes in particular and most all of the other pre-91 models, in general. I do NOT claim to have a great deal of experience on Gold Wings, Cruisers, ATC/ATVs and dirt bikes.


I have owned/ridden/maintained Honda motorcycles for 35 years. I have written five books on Honda repairs and collecting. I was a service manager for two Honda shops back in the 1980s.

VJMC (Vintage Japanese Motorcycle Club) of North America

VJMC newsletter, as editor for two years and as contributing editor currently.

3 years auto shop in high school, teacher's aide in Automotive Technology in Jr. College, Diesel mechanic course in college, self-taught mechanic and automotive writer.

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