Trail Rider Magazine

30 Trail Rider www.TrailRider.com So now let's take a look at a 250cc 2-stroke with a 40 horsepower, as we might fi nd in a good Enduro applica on. We will fi nd that although the peak power has been reduced when compared to the MX motor, the middle rpm ranges are now the priority, to be er deal with the compara ve lack of trac on we typically fi nd on an eastern Enduro or Hare Scrambles course. Although speed and ac- celera on are s ll important, there is also a need to fi nd grip in slippery rocks, roots, mud, wet grass, and leaves. So here we fi nd it is worth the trade-off of less peak power at the highest rpm's to gain a broader spread of power in the middle rpm range. This allows the rider to use a taller gear in a given circumstance, with less throt- tle needed at the same me, and this makes for much be er grip at the re in poor trac on condi ons as a result. So as we arrive at the 250cc 2-stroke for Tri- als, we fi nd that it's the lower rpm ranges that are priori zed over all others. As such, we might see the horsepower numbers to be only in the low to mid 20's, or less than half of the high rpm MX versions. Although this might sound to be too tame for many of us, don't be fooled. In actuality we fi nd these low rpm motors make trac on very eff ec vely. In fact, they'll likely surprise you with their ability to fi nd grip in mar- ginal trac on situa ons. It's worth men oning here that the 50hp mo- tor will likely need service and component re- placements much more frequently than the less stressed 25hp Trials motor. In my experience this can be about every 50 hours or so for the race bike compared to as much as 500 hours for the Trials machine. To con nue, up un l 50 or so years ago, the bikes of choice for Trials were mid to large dis- placement 4-stroke singles. With their heavy fl ywheels and long stroke designs, lots of low rpm torque and tractability helped fi nd trac on with the rather crude, rubber coated canvas res of the me. Over the years the bikes became lighter but there was never a need for much more peak power than they already had. Instead, the tuners focused on fi nding the best balance of fl ywheel iner a, gearing, and rpm ranges to provide the ut- most fl exibility to the riders in the largest variety of trac on condi ons. This mission statement has remained the goal right up through today. In the mid-Six- es, Sammy Miller le his venerable 4-stroke Bri sh single to devel- op a new light weight 2-stroke with the Spanish Bultaco factory. Six weeks later he debuted the prototype with a victory! In its very fi rst com- pe on ou ng and almost overnight, the Trials world went to lightweight 2-stroke singles. Over the years we have seen numerous brands of 2-stroke Trials bikes come and go from a variety of Euro- pean and a few Japanese factories as well. Even today we fi nd that the majority of modern Trials riders today are choosing the 2-stroke bikes for Trials. Honda has been the notable excep on to the rule. The Honda/Montesa 4RT has been at the top of the world for 10 years with Toni Bou at the controls. K eep your feet on the pegs! -Stu

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