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Yamaha YZF 1000 R1 MotoGP Replica

For 2004/05 Yamaha has released the third generation R1, and all I can say is, For starters, it has an entirely new engine that pumps out a claimed 180-ram air assisted horsepower at 12,500 rpm. You have to look back to the FZ 750 of 1985 for Yamaha’s first forward slanted five-valve engine. And sticking to their unique design, Yamaha’s engineers have tilted this year’s engine 10 degrees forward, for a total lean of 40 degrees from vertical.Inside the new cylinder head, the intake and exhaust valves have grown 5mm in diameter while shrinking in length. Both sets of valves have steeper angles and use stronger springs as the new engine revs some 2,000 rpm higher than the previous model. Opening and closing the 20 valves are new camshafts. Interestingly, the intake cams have more lift, while the exhaust cams now have less to reduce mechanical power loss. They have also been lightened 4% by the use of smaller journals, which allows them to spin faster. A hydraulic cam chain tensioner keeps the cam chain honest at the higher rpms.

Revised combustion chambers provide a 12.3:1 compression ratio, up from last year’s 11.8:1. Providing the spark, shorter CR9EK spark plugs stay well clear of the pistons. For 2004, piston diameter is enlarged to 77mm, while the piston skirt height has been reduced. Running in sleeveless cylinders, the bigger bore means a wider cylinder, even with a smaller 5mm gap between them. The connecting rods are now 2mm shorter at 34mm. The journals have also been reduced 2mm in size to help the crankshaft weigh in 16 percent lighter.

Carbonized for greater strength, the quicker revving crank is also 23.7mm narrower. During the pre-ride presentation, I found it interesting to learn how the connecting rods are produced. Using a fracture split process, the rods are made as one piece and split. This allows the surfaces to mate closer together for more strength, as the two pieces are mirror images of themselves.

In keeping with the stronger and lighter theme, this year’s clutch basket loses 5 percent of its weight. It’s also narrower, and uses six coil-type springs in place of last year’s diaphragm type clutch spring. Three of the cork friction plates have also been changed to a paper base to better deal with the heat. The new clutch transfers power to a close ratio gearbox that gives no fuss on the racetrack. Start shifting at lower rpm on the street, and it needs a decisive foot to show it who’s boss, but it’s never harsh.