TKM have introduced a new component to help extend the life of older engines. Grahame Buerworth reveals the details. The big end crank-pin is a small component which takes on a massive job and if it fails can result in a nasty repair bill. Over the years the use of the TKM BT82 has seen its maximum rev usage continually climb way past the 15,000 originally recommended for the engine and that puts more and more strain on the pin. Years ago when my son and I raced in the class I don’t think we even saw 15,000 on the rev counter. Yet these days 16,500rpm is not at all uncommon, although certainly not recommended, and of course that puts huge extra strain and wear on the engine. Over the years steps have been taken to make the engine ever stronger – revised con-rod, larger main bearings, different big- end pin design/heat treatment, revised pistons etc.
None of it performance enhancing but all making it stand extra grief and strain without going bang. But as engines get older and older some areas can start to deteriorate, especially if they are not serviced correctly and have for example worn crank main bearing journals or crank-pins pressed in slightly out of true causing worn and damaged big- end pin fit holes in the cranks. You can end up with crank halves with slightly loose/damaged holes for the crank-pin, main bearings loose on worn journals and even bearings moving fractionally in their worn crankcase housings. In fact a whole variety of similar very minor issues can create an engine which is not running as smoothly as it should. The resulting problems and vibrations can be a big-end crank-pin disaster waiting to happen. And of course add in the fact that some people grossly over-rev the engine and you can have a recipe for failure. So especially to help owners of engines in that situation Tal-Ko have now produced a new heavy duty crank-pin which is solid with just partial drilled domed ends.
Now let’s be clear this is not intended to make you go quicker and will not be fied to new engines or the Performance+ fully optimised engines Tal-Ko prepare for top level racing. It is intended as a cure/band aid for those units probably past their best which are still in use and which customers do not want to spend the extra money on parts like new crank halves. The new crank-pin is basically stronger and so will cope with that additional vibration and strain to give longer life. But do note it is effectively masking a problem, not curing it. The heavy duty crank-pins cost just a few pounds more than the standard item and are now available from Tal-Ko.