Maxed Out: C4MX YZ250F 5

Luc "Frenchie" Caouette got started in Eastern Canadian motocross by wrenching for Marco Dubé, and then working for the Two Wheel Kawasaki team, with Sean Hamblin. Along the way he learned English, as well as a ton about both engine and suspension work.

After passing a resumé to Erik Kehoe at Binghamton in the summer of '01, he got a call telling him that if he could get his work visa figured out, he had a spot at Yamaha of Troy. After dialing in those details, he joined the team late that year.

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So what went into the engine? You name it, and it's in there. Starting on the intake side, with a Twin Air flow kit (filter and billet cage, $150), as well as a different air boot that flows better and adds half a horsepower by itself ($55). There's also a carb mod ($150) combined with a float bowl change ($85) designed to eliminate any bogging on hard or flat landings. There's also a replacement needle ($25), as well as a different carb bore ($115), which adds mid-to-top power, and is recommended for MX only.

From the top down? There's a new spark plug ($14), and custom billet cams ($690) designed to boost bottom-to-mid power. They're mated with a Faction MX valve spring kit ($315). Frenchie really wants to make sure that there's no valve float, especially with a higher rev limit (from 13,500 to 14,200 RPM) provided by a JD ignition box ($650). As for the valves themselves, they're Faction MX high-compression one-piece valves ($885), and mated with DLC buckets ($500) for less wear and friction.

As for the head itself, it gets the porting treatment from C4MX ($400) for better flow, and for added life and better flow, it also gets copper valve seats and a five-ange valve face ($650).

Moving into the cylinder, you get a high-compression piston ($275), and DLC-coated wrist pin ($115). They're connected to the lower end via a stronger-than-stock Carillo rod ($280), and a C4MX crankshaft mod ($500) that makes it lighter than stock, and eliminates the counterbalancer and rebalances the crank for much snappier throttle response.

C4MX also eliminates the oil tank and lines with their oil tank kit ($140). To make shifting easier, reduce friction between the gears, as well as reduce heat and add more power, the transmission gets and ISF (Isotropic Superfinish) process to smooth everything out to factory standards ($400).

To finish it off the internals, and make sure there's no slipping and loss of power, there's a complete Hinson clutch setup, including the basket (H341 $289), inner hub (H142 $309), pressure plate (H070 $189), clutch plates, including fibers, steels, and springs (FSC141-9-001 $199), and a Hinson cover (C141 $159.99).

The exhaust? That belongs to FMF, and is one of their Factory 4.1 systems ($849).

Radiators are stock, but to keep things run cool under pressure, Frenchie bumps up from the stock 1.1 psi cap to a 1.8 psi cap ($37). Oils are from Maxima.

With the oil tank eliminated, and some high-digit components in the engine, a Works Connection skid plate seemed like a good idea.

As for the front suspension, the economy may be bad for some factory technicians, but it works out pretty well for consumers. C4MX has access to some former factory talent, and the forks were revalved ($180) and set up for more aggressive riding. Austin dig the action, both over braking bumps and the bigger jumps.