--- product_id: 50150788 title: "G4074 Colortune Single Plug Kit 14mm" brand: "gunson" price: "Β£252.60" currency: GBP in_stock: true reviews_count: 13 category: "Gunson" url: https://www.desertcart.co.uk/products/50150788-g4074-colortune-single-plug-kit-14mm store_origin: GB region: United Kingdom --- # Precision carburetor tuning via combustion color 14mm short reach plug & hex adaptor Fits most M14 threaded petrol engines G4074 Colortune Single Plug Kit 14mm **Brand:** gunson **Price:** Β£252.60 **Availability:** βœ… In Stock ## Summary > πŸ”₯ Tune smarter, drive farther β€” see the difference inside your engine! ## Quick Answers - **What is this?** G4074 Colortune Single Plug Kit 14mm by gunson - **How much does it cost?** Β£252.60 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.co.uk](https://www.desertcart.co.uk/products/50150788-g4074-colortune-single-plug-kit-14mm) ## Best For - gunson enthusiasts ## Why This Product - Trusted gunson brand quality - Free international shipping included - Worldwide delivery with tracking - 15-day hassle-free returns ## Key Features - β€’ **Boost Mileage & Performance:** Users report up to 150% increase in fuel efficiency and smoother throttle response. - β€’ **See Your Engine’s Heartbeat:** Visualize combustion chamber conditions instantly for pinpoint tuning. - β€’ **Made in the UK, Trusted Worldwide:** British-engineered quality combining ethical sourcing with expert manufacturing. - β€’ **Cut the Guesswork, Tune Like a Pro:** Eliminate trial-and-error carb adjustments with direct color-based mixture feedback. - β€’ **Universal Fit, Pro-Level Precision:** Compatible with most petrol/LPG engines using M14 plugs, plus extra adaptors for custom fits. ## Overview The Gunson G4074 Colortune Single Plug Kit is a precision automotive tuning tool designed for petrol and LPG engines with M14 threaded spark plugs. It enables real-time visual inspection of combustion chamber conditions through color analysis, allowing professional-grade carburetor and fuel mixture adjustments. Crafted in the UK with high-quality copper components, this kit includes a 14mm short reach plug and hexagonal adaptor, fitting most vehicles and offering optional adaptors for broader compatibility. Trusted by classic vehicle technicians and performance enthusiasts alike, it delivers measurable improvements in fuel efficiency and engine responsiveness. ## Description The Tune-up plug for Petrol/LPG 2 and 4 stroke engines with single, twin or multiple carburettors or fuel injection systems.The original and best tool for seeing what's happening inside the combustion chamber of the petrol engine. It allows you to see the combustion and to adjust the mixture by colour. Fits most petrol engines in standard form with additional adaptors available for vehicles with alternative sized spark plugs. A British tool company based in Warwickshire, United Kingdom. Gunson Tools draws on years of experience to introduce quality products which offer real value for money. All our products are responsibly sourced both from trusted ethical partners across the world PLUS (uniquely as an automotive tool brand) our own manufacturing base in the UK. Trusted quality products like Eezi-Bleed, ColourTune, Carbalancer and Eezi-lap are just a few names within the range. Combining our British manufacturing, our years of experience and vast expertise in the automotive sector helps us achieve our aim of bringing high quality tool solutions first to market and being No.1 choice for the Classic vehicle technician Review: 150% increase in milage! - I bought this to use to tune the carb on my custom motorcycle. I had changed the pipes and replaced the airbox with a velocity stack, which meant rejetting. I had gotten it tuned fairly well (I thought!) and had been riding it for about a year like that. After hearing about the Colortune, I thought I'd give it a try. Instantly it was obvious the needled needed to be adjusted, it was WAY too rich. I moved it a couple notches, got a nice blue color and put it all back together. I immediately rode better, with much better throttle response and power, but that was just based on how it felt to me. A week later I went on a road trip with the bike and when I stopped to get gas, based on the odometer I should have needed it, the take was still half full! Quick math showed I'd been getting 60 miles a gallon! In the years since I modified it, the best I ever got was 42. When I bought it, before modifications, it got 50 on the highway. I could not believe it. But three tanks later, I was getting the same results! Colortune is worth every penny. Its easy to use, and the difference in mileage and performance it made is awesome! Review: Star of the show - Great, a must have for tuning. Really great product. ## Features - Kit includes: 14mm Short reach plug and Hexagonal adaptor - Colortune will fit most vehicles fitted with M14 threaded plugs - Kit complete with instructions - Extra adaptor sizes available separately, please see Gunson Part Nos G4055E (18mm), G4055D (14mm long reach), G4055C (14mm tapered seat), G4055B (12mm), G4055A (10mm) - The complete Colortune kit is also available with the following adaptors G4171 (with 12mm Colortune Plug), G4172 (with 10mm Colortune Plug) - Automotive Tool ## Technical Specifications | Specification | Value | |---------------|-------| | ASIN | B0012MB4VE | | Best Sellers Rank | #396,621 in Automotive ( See Top 100 in Automotive ) #2,385 in Automotive Replacement Spark Plugs | | Brand | GUNSON | | Brand Name | GUNSON | | Compatible with Vehicle Type | Car | | Core Material | Copper | | Customer Reviews | 4.6 out of 5 stars 577 Reviews | | Gap Size | 14 Millimeters | | Global Trade Identification Number | 05018341740740 | | Included Components | 1 x Gunson Colortune 14 mm Kit Colortune Spark Plug Carburettor Mixture Tool | | Item Type Name | Gunson Colortune 14 mm Kit Colortune Spark Plug Carburettor Mixture Tool | | Item Weight | 0.15 Kilograms | | Manufacturer | Tool Connection (EU) | | Manufacturer Part Number | G4074 | | Model Number | G4074 | | Thread Size | 12 millimeters | | Top Material Type | Copper | | Unit Count | 1.0 Count | | Vehicle Service Type | Car | ## Product Details - **Brand:** GUNSON - **Core Material:** Copper - **Thread Size:** 12 millimeters - **Top Material Type:** Copper - **Vehicle Service Type:** Car ## Images ![G4074 Colortune Single Plug Kit 14mm - Image 1](https://m.media-amazon.com/images/I/710aUHECQJL.jpg) ![G4074 Colortune Single Plug Kit 14mm - Image 2](https://m.media-amazon.com/images/I/71uIZ6uZRUL.jpg) ![G4074 Colortune Single Plug Kit 14mm - Image 3](https://m.media-amazon.com/images/I/71INdVX7UEL.jpg) ![G4074 Colortune Single Plug Kit 14mm - Image 4](https://m.media-amazon.com/images/I/810wIQpqV8L.jpg) ![G4074 Colortune Single Plug Kit 14mm - Image 5](https://m.media-amazon.com/images/I/71LoOD2DumL.jpg) ## Questions & Answers **Q: what size adaptor do i need for spark plug autolite AP63 ?** A: It would be a good idea if you supplied the thread size on the spark plug you need info on, if you did that I could answer your question. **Q: Using a digital caliper, i measured the threaded portion of the spark plug and got a reading of 13.80mm. do i use the 14mm size colortune kit?** A: I would have to say yes you are correct, but I better add that just in case it is not you should check the thread pitch with guages or your caliper. Coarse thread is 2mm pitch and fine is 1.5mm fine. If you need any more info I'll check mine **Q: Will this tool work on a 72 Porsche engine. Or do I need adapters** A: I used it for 25 years on a '71 VW Super Beetle with the standard 1600 engine. It works like a charm. Mine was bought in the 80s from an adv. in Hot VWs. I still have the shipping bag with the nice black box. 'Never let me down. **Q: Will this work for a 70 gmc jimmy strait 6 2barrel carb , thanks.** A: I use this on my Mopar V8 440 from a '68 Chrysler 300. The 14mm thread. i recommend loosening up the plugs when the engine is cold and then (anti-seize) them back in not too tight. You could do all 8, but, for me, I am fine with just two on each side of my split plenum intake. ( If you have a split plenum design, check your runners on your intake so that you are really reading two from each carb side. Pretty funny if you happen to pick all four from the same carb circuit! For example, on RB engines, 3 and 5, 1 and 7, or 4 and 6, 1 and 8 are matched sides for a 4-barrel. So, 1 and 3, or, 2 and 4 would work fine.) Keep in mind the hot exhaust manifold/headers, so, pick the plugs you can get in without burning your fingers and heating up your plastic pipe (Gunson). After your engine is warmed up and you have done your vacuum or rev range or even AFR idle, etc., switch out the plug for the Gunson. If you can, wrap the plastic in the 1" DEI or similar heatshield. I used the Firesleeve. This will protect the flimsy black plastic. And, when done - don't take too long running the engine - take off the plastic parts and plug. Don't let heat soak kill your piece. ## Customer Reviews ### ⭐⭐⭐⭐⭐ 150% increase in milage! *by C***D on September 4, 2020* I bought this to use to tune the carb on my custom motorcycle. I had changed the pipes and replaced the airbox with a velocity stack, which meant rejetting. I had gotten it tuned fairly well (I thought!) and had been riding it for about a year like that. After hearing about the Colortune, I thought I'd give it a try. Instantly it was obvious the needled needed to be adjusted, it was WAY too rich. I moved it a couple notches, got a nice blue color and put it all back together. I immediately rode better, with much better throttle response and power, but that was just based on how it felt to me. A week later I went on a road trip with the bike and when I stopped to get gas, based on the odometer I should have needed it, the take was still half full! Quick math showed I'd been getting 60 miles a gallon! In the years since I modified it, the best I ever got was 42. When I bought it, before modifications, it got 50 on the highway. I could not believe it. But three tanks later, I was getting the same results! Colortune is worth every penny. Its easy to use, and the difference in mileage and performance it made is awesome! ### ⭐⭐⭐⭐⭐ Star of the show *by C***S on May 13, 2025* Great, a must have for tuning. Really great product. ### ⭐⭐⭐⭐ Nice product, poor packaging *by K***N on June 28, 2022* came in reasonable time, but NO protective packaging, item was in plastic bag and box inside was crushed. Luckily the parts themselves appear ok. Suggest vender put item in better more protective box. Update: tried the Colortune on my XKE... works great and allows me to really refine the SU carb settings. Would buy again. ## Frequently Bought Together - GUNSON G4074 Colortune Single Plug Kit 14mm - Gunson G4055B Adaptor Kit 12 mm --- ## Why Shop on Desertcart? - πŸ›’ **Trusted by 1.3+ Million Shoppers** β€” Serving international shoppers since 2016 - 🌍 **Shop Globally** β€” Access 737+ million products across 21 categories - πŸ’° **No Hidden Fees** β€” All customs, duties, and taxes included in the price - πŸ”„ **15-Day Free Returns** β€” Hassle-free returns (30 days for PRO members) - πŸ”’ **Secure Payments** β€” Trusted payment options with buyer protection - ⭐ **TrustPilot Rated 4.5/5** β€” Based on 8,000+ happy customer reviews **Shop now:** [https://www.desertcart.co.uk/products/50150788-g4074-colortune-single-plug-kit-14mm](https://www.desertcart.co.uk/products/50150788-g4074-colortune-single-plug-kit-14mm) --- *Product available on Desertcart United Kingdom* *Store origin: GB* *Last updated: 2026-05-22*