TKM Insight – Which drive-line?

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So you’ve decided you want to make the move to TKM for next season. But then there’s the big question – what type of drive-line to choose, TAG, clutched or direct drive?

So what are the differences? In general driving terms on the track there is little to tell because the clutch on the TAG & clutched models is always engaged like direct drive unless you come to an almost stop. However in the wet the clutch has the advantage of allowing you to brake and lock the rear wheels without the problem of the engine stopping which can be a problem on a direct drive. And of course the clutch gives you a huge advantage when something happens on the track. You can spin and re-join the race or come to a halt avoiding accidents and then just drive away providing of course you have set up the correct tickover so the engine does not stall. Here are some more detailed points:

TAG (Touch & Go)

FOR – The easiest with an on-board electric starter. An automatic centrifugal clutch so you just press the throttle and go. Ultra easy to start by the driver with stop start push buttons and quick re-starting should the engine die giving maximum confidence for the driver.

The engine is uprated with larger exhaust and raised compression to increase power and overcome the additional weight on the crankshaft of the starter system. Pole positions and wins at top championship level confirm its performance.

AGAINST – It adds about 4.5 kilos to the weight of the kart which is fine if the driver is well under the weight limit but could be a problem for drivers near the limit. It is more expensive to buy (about £450 extra) and more complicated to look after requiring good care to wiring to ensure no problems.

Clutched Drive

FOR – Gives all the ease of an automatic centrifugal clutch and the benefit that brings should you spin off, but without the complication and weight of TAG system. The engine is started by a mechanic with a remote hand-held electric starter unit (a bit like F1) and if the tickover is correctly set up then the engine should not stall if the driver spins off. It is only a shade heavier than direct drive and simple with no on-board wiring to worry about. If you don’t like the clutch or simply want to test it as a direct drive unit then it can quickly be converted by removing the clutch and fitting in its place a special long direct drive sprocket and nut.

AGAINST – You have a fairly heavy starter unit to carry around. If the engine does stall in a spin on the track then you can only re-start with this starter. Clutched engine costs about £120 more than direct drive plus extra cost of about £290 for the hand held starter. Purists will say it is slower than direct drive engine but a clutch has been used to win the British championship in the past so don’t take too much notice!

Direct Drive

FOR – The simplest, lightest and cheapest; less to go wrong making it idiot-proof. No wiring or battery chargers to worry about. Purists will say it’s quicker. Certainly gives the driver the most absolutely direct connection with engine and kart. You can use a smaller 9 tooth sprocket on tight tracks which the TAG & clutched units cannot.

AGAINST – It is a chore lifting and push starting. In the pits at least you can use a wheel pusher device to help, but if you spin on track then it is down to the driver to do it themselves which is hard work. Juniors will only get re-started on-track with a helper. A definite no if you have any back problem.

So over to you for final choice. For my money with a Junior I’d always go with a clutch, be it out-board or TAG started. It gives them the best possible chance.

For a Senior, the direct drive does have the advantage of simplicity but I’d still argue that having a clutch just makes it all so much easier and more pleasurable.