the ultimate collection of ultimate bikes




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                               The motor is 370cc's.  The difference from the 360, is that the crank pin is in a different location, giving a longer stroke.  This was to give it more torque.  The crank cases and sidecovers are sand-cast magnesium.  All the case screws including the centercase screws are titanium.  The gearbox is a five speed unit with hand cut gears and hollow shafts.  As with most works Yamahas of this era, the kick start lever is forged titanium.  All transmission and crankshaft nuts are machined from titanium.  Motor mount bolts and shift shaft are titanium.  The clutch actuating arm goes through the top of the motor instead of through the side like the production model.  This system gave a more positive clutch pull.  The exhaust is comprised of hydro-formed cone sections gas welded together.  The muffler is very small and does little to quiet the bike.



                                                                               The top triple clamp is cast magnesium, while the lower is machined from billet aluminum.  The fork tubes are knurled at the lower clamp for more grip and they are machined down just above the lower clamp for reduced weight.  All the pinch bolts are hand machined titanium.  There is a machined aluminum fitting fastened to the lower triple clamp that the fork gator is clamped to.  This prevents any binding that might occur.  The frame was inadequately gusseted at the steering stem.  This led to many frame failures.  Late in the season, US factory rider Pierre Karsmakers commissioned Pro-Fab to redesign and make a new frame.  The frame was so successful that Pierre won the final round of the Trans-am at Saddleback with one.  Yamaha immediately ordered 25 of them and even designed the 1975 worksbike after them.  Two of his bikes with that frame are in this collection.  The ignition coil is mounted right behind the steering stem and the black box is mounted between the front down tubes.



                               Fitted on this bike is the optional front mud fender.  It has an over-fender pop-riveted on the front and a rubber flap riveted on the rear.  Since the stock fender was so narrow, many riders opted for this set-up in all conditions.


                               The frame is tubular chrome moly with the backbone structure made from a series of fabricated plates welded together.  The frame was designed from a clean slate and far different than the 1973 model.  The shock has a hard anodized aluminum shock body and was internally adjustable with various valving jets.  The early shock bodys elongated and were sometimes replaced with steel.  The rear reservoir held nitrogen and acted as a spring.  It could be tuned by adjusting the nitrogen pressure.  The air box is made from very thin layers of fiberglass and the aluminum brackets are held by pop-rivets.  These had to be watched carefully because once the rivets came loose, they would allow dust to pass.  The air filter covers are  hand formed in aluminum, connected by a titanium thru bolt.


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