Gunson Colortune Kit: 10mm, 12mm or 14mm

Take the guesswork out of engine tuning with Gunson's colortune, the world famous glass topped spark plug that gives you a window into the combustion chamber so you can see the flame. Why is this important? The flame's color tells you the richness of the air fuel mixture. A yellow flame means a rich mixture and a blueish white flame a weaker mixture. A Bunsen blue flame is spot on. colortune is so damn simple that anyone can use it. Colortune is unaffected by ambient weather conditions because it works on the law of physics that gases burn with a certain color. Remember high school chemistry lab and the Bunsen burner. So stop reading plugs and start tuning by color.

The colortune kit includes a colortune, viewer scope, high tension leads, and cleaning brush.

Cleaning fluid no longer comes with the kit due to shipping restrictions. Use carb cleaner to remove carbon deposits from colortune.

The 14mm Colortune fits the majority of cars and bikes but to make sure check the cross reference table at the left or call John Abbott at 800 795 6958.

Colortune kit no longer comes with cleaning fluid. Use alcohol to clean.

How to choose between Colortune and an exhaust gas analyzer like Gastester. Use Colortune when you have multiple carbs and don't want to drill ports in exhaust manifolds and you have a clear line of sight to the top of the spark plug.

In a multiple carb application you must be able to associate an exhaust stream with a carb so you can adjust each carb's fuel mixture by measuring the carb's exhaust stream. If you just want to set the fuel mixture to it's correct strength without knowing what that strength is then use colortune.

If you want to know the air/fuel ratio's numeric value then use an exhaust gas analyzer like Gastester or a air fuel ratio meter like LM-1 also available from AEP Inc. at a very competitive price.

Information: The correctly proportioned mixture is - 14.7 parts of air by weight to 1 part of fuel. If there is perfect combustion, all the fuel will be burnt to produce carbon dioxide and water with no carbon monoxide or unburned fuel (hydrocarbons).

The carbon in the fuel burns with oxygen in the air to produce carbon monoxide (CO), which then burns with more oxygen to produce carbon dioxide (CO2).

Hydrogen in the fuel burns with the oxygen in the air to produce water (H2O) Nitrogen in the air passes through to the exhaust with little reaction.

When there is less air in the mixture, there is not enough oxygen to complete the burning process so some carbon monoxide is not changed to carbon dioxide and hydrocarbons (unburned fuel) may be present in the exhaust.

Carbon particles glow yellow in the combustion of a rich mixture and in severe cases you may see black carbon smoke in the exhaust.

When there is too much air in the mixture, it becomes more difficult to ignite, burns slower, and is therefore less efficient. The diluted mixture burns with a pale flame. Misfiring may occur and hydrocarbon levels in the exhaust gas will rise.

Carbon monoxide levels stay low because there is plenty of oxygen available to convert it to carbon dioxide.

Product Manuals

Colortune Instructions

Colortune Chart

Product Info Sheet

Gastester Instructions

Clickadjust Instructions

Carbalancer Instructions

Eezibleed Instructions




Proven over time

Over 50 years!

Order the right size

Look up your vehicle in the NGK product guide to makes sure you need a 14mm colortune. Most cars use 14mm plugs. If unsure ask me.

NGK Plugs

Use the first letter of the product code to determine the adapter. Remember colortune comes with 14mm threads.

  • A - 18mm
  • B - 14mm
  • C - 10mm
  • D - 12mm
  • J - 12mm

How to decode spark plug codes guide (NGK)

Carbalancer $29.95


Buy Carbalancer

Colortune Kits $69.95, 10mm, 12mm and 14mm


Colortune Kits
Buy Colortune

Colortune Kit

See the color of combustion through the glass top and tune with confidence

Gasteter $229.95


Buy Gastester

clickadjust $59.95


Buy clickadjust

Colortune adapters: 10mm, 12mm, 14mm Long Reach, 14mm Taper Slim, 18mm

Available for 14mm Colortune only.

These kits convert the thread on Colortune to fit most popular sizes of spark plugs fitted to most modern and classic cars, motorcycles, garden machinery and boats. Contents 1 x Thread Adaptor (10mm,12mm,14mm or18mm), 1 x Gas Seal Washer 1 x Hex Key (with 18mm adaptor only.

Colortune Adapter

10mm10mm long reach colortune adapter
12mm12mm long reach adapter
14mm Long Reach14mm long adapter
14mm Taper Slim14mm taper slim adapter
18mm18mm adapter