Last winter, one of our motocross customers met with me and asked, “Dave, how can I get more low and mid-range power and a little longer engine life without sacrificing the great top-end that I now enjoy?” Since he was running an air cooled Yamaha Blaster, I told him, “Sell it and get yourself a water-cooled bike.”
Anyone who has spent much time tinkering with the little Yamaha will run into a dilemma — get the little bugger to breath well enough to make respectable power and you end up with a narrow power band and relatively short top-end life. We had tried different porting schemes, compression ratios, pipes, carbs and reeds with varying degrees of success, but none was satisfactory. We had also tried piston coatings from a couple of sources, but had durability problems with those coatings. We then made a telephone call to Swain Tech Coatings. Dan explained that they had developed a process called “Ion Bonding”. The bottom layer of the thermal barrier coating actually becomes part of the substrate, or metal being coated. This eliminates the “flaking” we had seen on other coating companies’ products. The folks at Swain also told about some of the other Swain Tech Coatings besides thermal barriers. These include PC-9ä low friction coating for piston skirts, Black Body Emitter (BBE) coating for the outside engine surfaces, and Flow Coat for intake ports.
At the time, our customer had two identically-prepared engines that we were swapping back and forth as they became tired. We tore down both, inspecting them and determining that both were in need of a complete rebuild. The first engine was rebuilt normally — rebuilt crank, new seals, cylinder re-bored and fitted with new pistons and rings.
The second engine was done the same way, except that we first had Swain Tech Coatings coat all of the major engine components. We elected to have the piston dome, combustion chamber and exhaust port coated with TBC™ Thermal Barrier Coating. This .002″ coating keeps heat where it belongs — in the combustion chamber making horsepower, instead of letting it dissipate into the piston, head and cylinder, where it can cause metal fatigue and melting. The piston skirt was coated with PC-9 low friction coating. Cylinder head cooling fins and barrel were coated with BBE to get rid of heat more efficiently. Next, the barrel was rebored and the newly coated piston fit.
Once the engine was re-assembled and installed in place of the uncoated engine, the results astonished us! With the uncoated engine, gear selection had to be right on. Running the little Yamaha into a corner in fourth gear instead of third resulted in a big bog and lots of clutch lever action to get out of the corner. With the “new” coated engine, we found approximately the same top-end, but pulling power increased dramatically down lower in the rev range. If you found yourself mid-corner in too high a gear, the motor would now just let you “grunt” it out of the corner. The difference is so great between the two motors that the customer actually whines whenever we have to switch engines on him.
Engine component life seems to have increased one and one half to two times — keeping rebuilding costs down. Since then, we have given the same treatment to several other ATV engines, including a pair of Banshees, LT 250 and, of course, the Honda 250R. Although none of these had quite as dramatic results as the Blaster, they all had a noticeable torque and horsepower increase that made the money and time a good investment. We have found that the increased durability alone is enough to justify the coat treatment that our shop now sells to every serious race customer.