Engine – Oils, Fueling and Electrical system

Basic information and guides on your TM Racing machines engine oils, quantities and oil change routines, fuel and fueling systems, electrical components and devices and some ‘need-to-know’ maintenance for 4-stroke engines.


2-Stroke Engine Machines.

Fuel required:-

Super Unleaded – minimum 97 octane.

Premix Oil Ratios:-

Synthetic racing premix oil mixed at 32:1- 40:1 = (this equates to 500ml – 600ml of oil added to 20 Liters of fresh fuel )

Spark Plug Designation:-

85cc / 125cc / 144cc engines require an NGK BR9 EG spark plug. NOTE 2013 onward 85cc Machines require an NGK BR9ECMIX spark plug  –

NOTE: it is advised, in light of some issues over the past few years with various manufacturers and models with tip attachment failures, that 125cc and 144cc be updated to an NGK R7376-9 plug (NGK stock code 7763) that features a differing grounding. It is advised to fit this plug after the running in process has been completed.

Electrode gap = 0.7mm.

250cc / 300cc engines require an NGK BR8 EG plug.

Electrode gap = 0.7mm.

Gearbox Oil:-

80w0r 85W gearbox oil designed for ‘wet clutch’ use or an Automatic Transmission Fluid (ATF). We recommend Spectro 85W Gear Oil

Gearbox oil quantities required are:

85cc/125cc/144cc = 500ml >2006 / 600ml 2007>

250cc/300cc = 650/700 ml.


Keihin PWK / PWM carburetors.

In normal operating circumstances the only changes needed to be made to your TM Racing 2-Stroke powered machines carburetor will be alterations to your main jet and your needle clip position, rarely your fuel/air mixture once set correctly, dependent on track conditions and operating temperature, please refer to your TM Racing dealer for more information regarding ‘jetting’ your TM Racing machine before proceeding with altering any of these settings, your TM dealer can explain to you the benefits of correct jetting and how to ‘read’ what your engine and spark plug color is telling you to do.

WARNING: correct jetting will allow your TM Racing engine to perform at its best in the conditions required, however, do not attempt to alter these settings with little knowledge or understanding of how these changes affect the behavior of your engine and the consequences that these changes can lead to. Making an error in carburetor settings will cause severe damage to your engine, If unsure contact your TM Racing dealer or TM UK.

NOTE: on 2-Stroke Enduro machines which normally operate with a ‘tick-over’ it may ensure cleaner running of you TM Racing machine if you decrese the pilot jet size to compensate for the increase in fuel/air at low rpm’s. The idle speed screw on the Keihin PWK/PWM carburetor is effectively just a device to lift the ‘slide’, therefore the ‘throttle’ is being held open by the idle  adjuster screw, essentially you are running on part throttle even when you have the throttle closed, this can lead to the symptoms of ‘rich’ running at low rpm’s and can cause hesitancy (bog) from the engine, decreasing the pilot jet size from 42 down to 40 or 38 will counteract this effect and the bike will run correctly. Remember always keep the the carburetor clean and drain after washing to ensure no moisture is trapped inside, moisture can lead to bad running and corrosion of the internal components.

4-Stroke Engine Machines.

Fuel Required:-

Super Unleaded – minimum 97 octane.

Spark Plug Designation:-

250cc / 400cc / 450cc / 530cc / 660cc.

NGK CR8 E – Electrode gap 0.7mm.

250cc Fuel Injected Machines – NGK ROO45J-10

450xx Fuel Injected Machines – NGK CR9 EIX

Battery for Electric Start Equipped Machines:-

Yuasa YTX7L-BS

Engine Oil:-

Running-in period = High quality semi synthetic 20w/50 racing motorcycle oil for use with ‘wet clutches’.

Post running-in period = High quality semi/fully synthetic 20w/50 racing motorcycle oil for use with ‘wet clutches’.

Engine oil quantities are:-

250cc / 400cc / 450cc / 530cc :-

Oil change = 1.300 liters.

Oil and oil filter change = 1.350 liters.

Complete rebuild = 1.400 liters.

250cc Fi models:-

Oil change = 1.200 liters.

Oil and oil filter change = 1.250 liters.

Complete rebuild = 1.300 liters.

NOTE: Whilst completing oil changes on your TM Racing 4-Stroke machine you must ensure that the oil level in the inspection window is always visible before and during engine running. Ideally the oil level should be showing as 3/4’s full in the inspection window at idle, upon increasing the engine rpm’s the oil level should lower slightly as the oil pump increases its flow rate around the engine, once the engine has settled back to idle the oil level should return back to 3/4’s full in the window, If not please add more oil until the desired measurement is achieved or slightly exceeded. Warning: due to the position of the sight glass it is possible for an air pocket to occur in the top of the sight glass, this can lead to a false reading and the oil level could be higher than suggested, please take care when filling to ensure you do not overfill or under fill. Please refer to your TM Racing user manual for more information.

Valve Clearances

250cc / 400cc / 450cc / 530cc / 660cc  =

Inlet 0.10mm >  0.15mm -/- Exhaust 0.15mm < 0.20mm

250cc Fi =

Inlet 0.10mm > 0.15mm mm  -/- Exhaust 0.15mm > 0.20mm


Mikuni TDMR 36/39//41 – Keihin FCRD 39/41

As with the two stroke machines the carburetor settings should need little adjustment, the carburetors used on TM Racing 4-Stroke machines are very complex and should not be tampered with by inexperienced users, please refer to you TM Racing dealer for more information on these carburetors and for any technical help you may require with any running errors of the fuelling system. Remember always keep your carburetor clean and drain it after washing to ensure no moisture is trapped inside, this can lead to bad running and corrosion of the internal components.

Electronic Fuel Injection Systems.

Electronically Fuel injected machines require little in the way of maintenance and set-up, on TM Racing EFI equipped machines the fuel is filtered upon entering the fuel pump, to remove any impurities or particles in the fuel, the fuel is then pumped under high pressure through yet another finer filtration system to the main fuel line into the throttle body and then into the injector, the injector then atomizes the fuel into the oncoming air stream and enters the combustion chamber. The metering and volume of fuel injected into the engine is controlled by the ECU which ‘pulses’ and times the delivery of the fuel supply, the ECU monitors throttle position, engine speed, cooling system temperature, air pressure, air speed and a number of other factors to calculate how much fuel is required at any given time, this metering system can adjust itself to one of its set parameters in fractions of a second and is a far more economical approach to engine fueling, whilst not only regulating the fuel supply more economically further reductions in fuel usage are also gained from not having a ‘float chamber’ like a carburetor from which fuel can escape through the venting system.

The main advantage of Electronic Fuel Injection system, from a riders perspective, is that the electronic control of the fuel supply eliminates hesitation (bogging) that is commonly found in carburetor 4-Stroke machines and also the risk of engine stalling is lessened (although this is electronically monitored for safety) due to the electronics ability to alter the fueling characteristics of the engine and keep it running. A conventional ‘mechanical’ carburetor with a ‘float bowl’ will lose its fuel from its vent pipes and its fueling characteristics will change as it cannot utilize its carburetor jets unless they are bathed in fuel, this then leads to engine stall and increases the difficulty of re-starting the machine under high temperatures.

TM Racing’s policy of ensuring only the best components are used on their machines limits the use for changes to the Electronic Fuel Injection system, with components of exceptional quality, HGS exhaust systems for example, being fitted to the machine as a ‘standard’ part there is no need to ‘upgrade’ components like many other manufacturers machines and alter the working components of the engine, therefore altering the components that are factored in the metering devices of the ECU. The ECU fitted to TM Racing machines is adaptable to a very small degree and will compensate for minuscule changes to the machines working characteristics without the need for program interfacing (re-mapping), this occurs by the ECU using the readings from the onboard sensors and correcting the fuel supply to a level which it calculates to be closer to the optimum setting. Whilst this type of system can overcome very small changes from the stock parameters it is not infinitely calculating or self intelligent, the parameters it can change to are determined by the TM Racing programming and the ECU is limited to those tiny adjustments only, huge changes in elevation and oxygen reduction for example will be too great for the system to overcome with the pre-installed parameters and re-mapping of the ECU will need to take place, however, in the real world these extreme examples are not likely to occur and the need to interface with the ECU is not necessary or recommended.

If any problems occur with your TM Racing EFI equipped machine it should be taken to your TM Racing dealer for inspection and diagnostic test immediately.

WARNING: TM Racing does not advise alterations to the Electronic Fuel Injection system, its components or the pre-installed ECU parameters. This electronic device has been pre-programmed by TM Racing to give your TM Racing machine the maximum performance, reliability and safety, Failure to adhere to this warning could lead to engine component failure and/or injury.

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