Briggs 206 Tech: Proper Motor Mounting
Mount your engine to provide optimum performance
If you race in any four-cycle class, you’ve heard countless times about the need to maintain momentum. Low horsepower demands the most efficient use of the limited energy available.
I remember having a long discussion with engine builder Paul Leary about the need to get as much power as possible from the output shaft of the engine to the rear wheels. I asked for a more in-depth lesson. Paul laughed about the common conflict that occurs under any pit awning. As he tells it…the driver always complains that the kart is either too loose or pushes like a boat, and that the engine is down on power. That’s their excuse. Of course, the mechanic responds that the driver isn’t taking the corners correctly and is over-driving the kart, but her or she also agrees that the motor is down on power. It’s obviously not the set-up, right? Finally, the engine builder, who ran the powerplant on his dyno and knows the exact horsepower numbers, has looked over the post-session data and is adamant that the chassis is bound up and lugging the motor down, and agrees with the mechanic that the driver needs to adjust his or her lines and corner approaches. It’s a story as old as the sport. And…the truth is in there somewhere, and is likely a mixture of everything.
After hearing Leary’s description, I wholeheartedly agreed with his concept, considering that I’ve had many a conversation with the three players of any racing effort and they’ve all blamed the other two from time to time. The bottom line though, from all three sides, is the ability to maintain all the power and momentum available. The engine builder provides the best power they possibly can. That’s why they spend so much time tweaking, grinding, and running the dyno. The mechanic is always searching for that sweet spot where the kart turns in aggressively, jacks the right amount of weight and rotates itself through the corner, wasting as little speed as possible while maximizing forward bite on exit. The driver, of course, is always focused on the perfect line where the least amount of momentum is spent.
This was a bit of a revelation to me when Paul first sat me down back in 2002 to offer his gospel. First and foremost, in terms of maximizing horsepower, Paul insisted, was the assembly of the kart and the installation of the engine. At the time, say he was producing a 125cc shifter with 43 hp, the ultimate goal was to have all of that 43 hp making its way to the rear wheels. That, however, is not possible due to all the components that deliver that power taking a little along the way. The key is to minimize this loss through every component, and this is why kart preparation and engine installation is so important, and it’s why every Briggs 206 racers needs to read the article (link below) in regards to motor mounting. Power is lost everywhere on its route from the output shaft of the engine to the contact patch between the rear wheels and the pavement. So, the key is to minimize that loss.
Friction and alignment are either your friends or your enemies. Think of all the components where horsepower is lost, beginning with the clutch set-up and then the transfer to the chain, which must be in good shape and lubricated, and in the proper alignment with the rear gear. Then, gear condition is a minor factor, as is axle alignment and bearing freeness. How much power are you losing if your rear axle won’t spin freely for days. Put it all together and you’ll have gaining a great deal of lost horsepower, which will likely give you the tenths of a second you might be leaving back at the shop.
Briggs Racing cares about your racing experience, so make sure to give a read of this article that discusses proper engine mounting: