Formula TKM regulations have a small but important amendment coming into force on September 23rd, 2022, which will underline the need to ensure that piston rings are completely free and not coked in place.

The regulation was first brought in many years ago when tuners tried to gain an advantage through rings coked in place with carbon. The rule created made it clear that rings should be predominately free but allowed up to 50% to allow for accidental gumming up.

However, in recent weeks it has become clear that certain engines have started to appear again with these stuck rings, gaining an advantage. So, in the interest of fair play the rule has been amended with Motorsport UK approval to make it crystal clear piston rings should be totally free.

The amended rule with deleted words underlined and highlighted in red is as follows:

D3.4.28  Piston rings must at all times remain predominately free (50% or more) to operate in the manner in which they were designed and supplied. It is the responsibility of the driver to ensure that the rings are not ‘coked’ in place with carbon or prevented from their normal ‘spring’ effect by other methods. The rings must be appropriate to the piston size used and have a maximum ring gap of 0.5mm when measured with the ring placed squarely 5-10mm down from the top of the cylinder bore. Only the standard unmodified earless type piston cir-clips as supplied by Tal-Ko must be used. The Extreme 115cc engine uses one piston ring, the Junior 100cc engine may use one or two piston rings. The bottom piston ring for the Junior 100cc engine can be removed for racing if required.

Announcing the amendment TKM boss Alan Turney explained: “We left the 50% margin to help possibly a clubbie driver who had not realised this had happened on an engine with many hours of running. It has worked well for years but now we have a fresh outbreak so we have no choice but to be absolutely clear that piston rings must be free at all times.”

He added: “The reality is that on the dozens of engines we service we rarely find rings that are stuck in the groove”. We want racing to be fair for all and of course one of the dangers of coked in rings is that it can lead to expensive engine failures.”

How can I check my rings? Most competent drivers / mechanics will know how to remove the cylinder head and barrel to check the piston. If a ring is slightly gummed in place, it can be easily freed off. Make sure you hold the ring compressed in its groove and aligned with the piston peg when putting the barrel back on.

Alternatively, Tal-Ko will do a quick free of charge check on any engine taken to the factory for a piston ring check.