Two small changes have been made to the engine regs for TKM you might just have missed. Grahame Butterworth explains.
If you’ve read the 2015 regs and engine fiche, you’ll have spotted these changes. But for everyone else, here’s a quick insight. First to pistons on Junior engines. For many years we have had a situation where the Extreme 115cc engine uses a single ring piston while the Juniors remain on twin ring. Now that is changing. The decision has been taken to simplify this situation for the benefit of drivers and scrutineers. TKM testing has shown no quantifiable difference in performance between one or two piston rings and no increase in piston and/or cylinder wear. In reality these days you will find very few, if any, other kart racing 2-strokes using twin ring pistons. So with immediate effect it is permied to remove the boom piston ring in the Junior BT82 100cc engine if desired. Note 100cc Junior pistons from Tal-Ko and those fied in new engines will have two rings fied.
The removal of the lower ring is down to driver or engine builder Don’t expect to suddenly find a performance increase in removing the boom ring because as I’ve said we can find no measurable gain from removing it. And remember that with no boom ring the seal of the top ring is even more critical. That makes the short-term easier but there is also a longer term solution. At some point in the future when stocks of the current twin ring 100cc pistons are finished, we’ll switch to the supply and fiing to new Junior engines of simpler single ring pistons. These new single ring pistons are slightly cheaper to manufacture and so will save you some money. But they won’t be available for some time so carry on with the current twin ring piston until they are available and make your own choice on whether to have one or two rings in place. And whatever rings you have in place they must still be at least 50 per cent free to move in the ring groove.
Next to big end crank pins, a small component which takes on a massive job, and can result in catastrophic damage if it fails. They have been made stronger over the years to stand the extra strain, and now there is a new one aimed specifically at those engines past their best. It means for a few extra pounds you can keep a worn old engine in use without having to pay out lots on new parts. Interested? I’ll explain more next month.