Letter From Europe
LETTER FROM Europe
ROUNDUP
Bimota's FZ750-powered YB4
Most of the world would be happy with a bike as good as the Yamaha FZ750, but not Bimota chassis designer Federico Martini. The case in point: The FZ750 Yamaha-engined Bimota YB4, as of now, is being developed along the same lines as the DB1 Ducati-engined Bimota.
The YB4’s race debut at Mugello in mid-June was aborted because of problems with the factory race-kitted engine. Therefore, Martini plans a series of ever-tougher tests for the new model in competition. culminating with an entry in the gruelling Bol d’Or 24 Hour classic at Paul Ricard in September. The YB4 is the first Bimota prototype streetbike with a fabricated alloy beam frame, and Martini is insistent on even more lengthy and rigorous testing procedures before this type of chassis is offered to the public in production form.
At the YB4’s first track-test session at Misano, I had the opportunity to ride the bike. As was expected, it turned out to be compact and quick-handling in true Bimota tradition, but not as twitchy or “nervous” as the lighter, twincylinder DB1. Martini has tipped the engine back slightly in the chassis to achieve a 56-inch wheelbase, with 16-inch wheels. Total weight of the YB4 in TT1 form (with electric starter, as required under Italian TT 1 rules) is 370 pounds with oil and water. Martini expects to reduce this considerably once the initial testing is complete.
Meanwhile, work is continuing on the YB5, an FJ 1200 Yamaha-engined bike, which will be launched at the Cologne Show in September, along with the DB 1 -S, a street version of the Ducati-engined machine that uses Bimota-developed engineperformance parts. With the DB1 selling well all over the world, it appears that Bimota is now fully in control of its destiny once again after repaying outstanding debts.
One more Moko
Prolific Swiss engineer Hansi Hilti’s Moko company has turned its attentions on a Yamaha. The muscular street rod is based on the tuned version of the XS650 twin-cylinder engine that took the Bollhalder brothers to the World Sidecar MX title in 1983/84. Bored and stroked from the original 75-by-74mm dimensions to 88-by-88mm for a capacity of 1078cc, the Moko-Yamaha produces 98 bhp at the rear wheel, at 8000 rpm. The vibration at those revs is pretty massive, but if you keep the revs down below 6000, the engine is relatively smooth—and it has enough torque to pull the side off a Swiss Alp.
Housed in a Moko spine-type frame, the engine runs a mild, 8.5: Î compression ratio and breathes through a pair of 38mm DelTOrtos. Dry weight with a full tank of gas is just 436 pounds, and the 16-inch front wheel (with an 1 8-inch rear) contributes to quick and responsive handling. Riding it is a bit like driv ing a two-wheeled racing tractor.
Alan Cathcart
