TM 85/100 2013-up Set up Info

Important Information On The 2013 onward TM Racing 85cc MX Machines.

Please Note:


 It is advised that for conditions between sea level and 3000 ft all 2013/14 85cc machines be fitted with the Mikuni carb require a 230 size main jet, 2014 onward models with the Keihin carb will require a main jet size ideally between 125-130, this will ensure adequate fueling and lubrication is achieved and allow for conditions and temperature variancies in our climate, the performance of the machine will not be affected, it will in fact be improved and increase longevity of the internal components of your TM Racing machines race engine. Please ensure regular plug color checks are performed to ensure correct running in altering ground conditions, track surfaces and temperatures/elevation ranges.
Please note that super unleaded fuel must be used at all times, this fuel should be mixed with a high quality two stroke racing synthetic premix lubricant to a ratio of 32:1. We recommend Spectro SX2 Platinum.


When replacing pistons and/or piston rings please ensure that the correct ring end gap of 0.25mm > 0.30mm is achieved, if the ring gap is smaller than these specified measurement the ring end gap must be enlarged. The piston ring end gap can easily be increased using a small carbide stone to grind the ring and achieve the correct gap, please ensure after using any tool to remove material from the piston ring that all burrs and rough edges/corners are removed and the ends of the rings are clean and burr free before fitting the piston ring into the piston, please check for free movement of the piston ring within the piston ring gap on the piston. As this 85cc engine has been designed to give the required high performance that has come to be expected from TM Racing’s high rpm two stroke machines it is advised that the piston be changed at regular intervals with piston ring changes in between. It is advised that under ‘normal’ operating conditions that the piston ring should be changed at approximately 6 hours, the piston should be changed at 10-12 hour intervals with a good rider competing on the machine, please note that under harder use conditions, ie sand or extreme temperature variations this time be reduced.
Failure to ensure the correct piston ring end gap is achieved during assembly and that piston ring and complete piston change intervals are adhered to will lead to premature failure and engine damage.
NOTE: Please ensure only genuine TM Racing parts are used to service your machine, we are aware of a number of pistons available as ‘aftermarket’ or ‘replica’ options for the TM 85 MX machine are in circulation. However, we have found that some of these pistons are not the same as the factory fitted item, in fact they are very different in many aspects, mainly overall height of the piston (depth of skirt below wrist pin area), lack of the rear ‘cut-out’ on the back of the piston to aid the ‘boost port’ in the cylinder and some are minus the exhaust bridge lubrication holes in the front of the piston. Please do not fit these pistons, poor performance and damage to your machine will occur.


When fitting new pistons it must be noted that the correct squish values must be obtained to ensure correct running of the engine and to ensure premature engine failure does not occur due to over compression and overheating scenarios. The correct squish measurements and cylinder ‘deck heights’ for the 85cc engine are listed below. These figure can be achieved by using altering thickness base gaskets that are readily available from TM Racing dealers.

2013> 85cc Engine ideal measurements are: Squish = 0.62mm / Deck Height = -0.80mm

Failure to adhere to the correct squish measurements could lead to engine failure and damage.


Please use genuine TM Racing spare parts in your TM Racing machines, using inferior parts could lead to premature engine failure and or damage to persons, the use of non genuine spare parts will also invalidate any warranty on your TM Racing machine.

Comments are closed.