I think one of the things I like about building bikes is that it's essentially product development. You are finding ways to improve every aspect of performance while tuning the bike to your specific riding style, and track conditions..
The first, single most important tuning mod to a motocross bike is to have the suspension re-sprung for your specific weight, and re-valved for your track conditions and/or handling preferences. Getting your suspension set up right makes all the difference in your confidence level on the track. We use Enzo racing for our suspension work.
I love the playfulness of a 250cc, although I find the stock 34hp to come up a little short. For me, the sweet spot in the go-department is more like 42hp. To get there we installed a WMI prepared race head, with a high compression piston and more aggressive cams. This raises the compression to 14:1 and increases the redline to 13,600 rpm. Throttle response is snappier, it makes more power through the entire rev-range, and loves to over-rev (which the stock YZ motor certainly does not).
To match the performance gains in the race head, we use the FMF megabomb titanium header, and 4.1 carbon fiber muffler. It allows the bike to breath better and make more power.
To make it quicker, we went with a 50T Renthal rear sprocket, which lowers the gear ratio slightly to match the top speed on the fastest part of our track. You don't want the bike geared taller than the track's top speed, as the lower the bike is geared, the quicker it can accelerate to it's top speed.
To make it stop faster, we installed an oversized 270mm front brake rotor. This provides a lot more stopping power with less effort. You can literally stand this bike on the front wheel with one finger while braking. Being able to drop anchor when needed, really increases your confidence when you're comin' in too hot!
That's the short-and-sweet as far as the tuning is concerned. Now let's look at the rider's controls...
A lap timer is integrated into the handlebar pad. You can time your motos and/or record individual lap times that you can review after each moto. This is good info if you are working on your endurance, or your speed (or both). The lower gauge is the hour meter for the motor, so you can keep track of your maintenance intervals.
Your left hand is controlling the clutch. The green button trips the lap timer. The tiny red lever underneath is the 'hot-start' lever that helps you get the bike started. And the big red button that says Engine Stop, ...stops the engine.
Your right hand is controlling the throttle and the front brake. The yellow switch controls the Vortex ignition, which allows you to flip between 2 of 10 possible different ignition maps. You can switch on the fly while you are riding, and actually change the power curve of the motor. I personally like the 'high compression map #5' most of the time - it just goes ballistic at the top of the rev range. Although if you're tired, or the track is slick, you can switch to the mellower map#1.
Your left foot controls the transmission. Most bikes have a 5-speed gearbox, with a 1 down, four up shift pattern.
Your right foot controls the rear brake.
You get everything right, and the result becomes greater than the sum of the parts. A -really- well set up bike is just magic. It's an extension of your body, making you feel like superman (or wonder woman?).
TR
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Labels: Moto
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