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Tillotson Racing T4 (Senior/Junior) M.Y. 2025: the reference 4-stroke kart of the T4 Series one-brand series
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TILLOTSON RACING T4 (SENIOR/JUNIOR) M.Y. 2025: THE REFERENCE 4-STROKE KART OF THE T4 SERIES ONE-BRAND SERIES
HOMOLOGATION
The Tillotson Racing T4 is specially designed to race in the T4 Series, a single-make championship held in 40 countries, and is used in both the Junior and Senior classes. Although developed for use in the Irish manufacturer’s single-make competitions, both chassis and engine are approved to FIA Karting standards. In detail, the chassis has the approval number 006-CH-09 CIK-FIA, while the engine is a TPP-225RS-02, 042-AIE-22. According to Tillotson, the products have nevertheless undergone the FIA Karting approval process to certify compliance with international quality and safety standards.
TUBES DIAMETER
The T4 frame is built with 30 mm diameter, 2 mm thick tubing, while the wheelbase measures 1,050 mm. The entire structure, hand-welded, is based on a Racing chassis originally designed for 2-stroke engines, but fully redeveloped to accommodate a 4-stroke engine, which is bulkier and presents challenges completely different from those of a 2-stroke engine.
ENGINE
The engine of the T4 is a 225 cc 4-stroke, the Tillotson TPP-225RS-02 model, developed specifically for the T4 Series and paired with two different versions of bowl-type carburettor depending on the class: FM22-1A for Senior and FM22-4A for Junior. This engine features digital ignition with a rev limiter set at 7,500 rpm, and a recoil start system.
START
The Tillotson engine powering the T4 is fitted with a recoil starter. To start it, switch on the ignition and then pull the cord to set the engine in motion. Thanks to the centrifugal clutch with which the engine is equipped, the kart can remain stationary while the engine is running, unlike direct-drive karts where the engine must be switched off.
Tillotson’s T4 project, launched in 2019, was created to provide an ideal bridge between rental and racing karting, combining the practicality and low costs of rental karts with the driving feel of traditional racing karts. To achieve this, Tillotson – a historic Irish manufacturer renowned for its diaphragm carburettors for two-stroke engines – worked on two fronts: on one side, it developed a range of karts with Racing chassis paired with four-stroke engines designed and manufactured entirely in-house, aimed at ensuring ease of management and low running costs without sacrificing a driving experience similar to that of two-stroke karts; on the other, it created and promoted the T4 Series, single-make championships now active in over 40 countries, with technical regulations that guarantee equal performance and cost control through the use of “long-life” and standardised components.The undisputed protagonist of this project is the Tillotson Racing T4 (the first version of which was already the subject of our analysis in 2019; to learn more, see “Under Review | T4-C1. The ideal kart for everyone signed by Tillotson”). The kart combines an FIA Karting-approved chassis with the Tillotson Racing TPP-225RS-02 engine, a 225 cc, 15 HP, 4-stroke, used in both the Junior and Senior classes. The two classes share the same technical base but differ in certain regulations: the minimum overall weight (kart plus driver) is 140 kg for Junior and 158 kg for Senior. In addition, the bowl carburettor configuration varies, with the FM22-1A model used in Senior and the FM22-4A in Junior. In these slides, we analyse the Model Year 2025 version, which introduces, among other updates, a newly approved chassis fitted with redesigned fairings and upgraded components (such as rims), and an engine equipped with an FM22 bowl-type carburettor and a raised rev limiter set at 7,500 rpm.
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