Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/126773
RZ350 (Continued from page 19) one who will remain nameless. This particular friend is a wizard mechanic, a man whocan make stock-appearing motOrcycles run quite well. His RZ is a case in point. In comes, from the factory, with main and pi lot jets one size richer than the U.S.-legal version, and its pipes, like the pipes installed on bikes destined to everyplace except the U.S., hold no catalytic conveners. Those pipes are lighter, 5.5 pounds lighter to be exact, but otherwIse look like the stock U.S. versions. Beyond that, this man's RZ350 has 1.25mm milled off the head, standard U.S. gearing (two more teeth on the rear sprocket than a Euro-model), and some careful poning. The standard cy linder has a bridged intake pon, with a left and right window; our man kept each pon's width and height overall stOck but removed the bridge, creatingone large window. He matched the exhaust pons to the powervalve assemblies, widening the exhaust pon of each cylinder at its top, while.majntaining stock pon height. Then he reshaped the transfer pons, removing metal to change the smooth arc each pon usuaJIy makes into the cylinder; the reshaped pons make abrupt turns into the cylinder instead. The poning alone, our friend told us, killed the bike's mid-range power. But milling the head restored the punch. He wasn't kidding. This motorcycle was the torq uiest RZ we rode all day, running out of power at 9500 rpm but -pulling very strongly when powershifted at that rpm, and at every rpm above 7500. The bike's best pass was 12.75 sec. @ 104.89 mph. Best of all, this motorcycle was as quiet as stock, non-offensive, and fast. Our friend wondered how his bike would run with Toomey pipes installed. It sounded interesting to us, and we tried it. Jelling remained unchanged, with the airbox in place. Sometimes it's easy to tell when you've got a good combination, and this was one of those times. With the Toomey pipes the Euro RZ stood straight up when the throttle was rolled on from 5000 rpm; it shot out of the stan when the clutch was slipped, and accelerated much harder. The best pass? 12.20 sec. @ 111.38 mph. Those results made us wonder how well the Spec II pipes would work on the Euro RZ. The answer was 12.54 sec. @ 106.13 mph. That's the price one pays for quiet pipes; we also believe the Spec II bike with milled head and bigger carbs didn't run better because it was jelled far too rich. The next logical move would have been to run the Euro bike with the RSCINoguchi pipes, but we ran out of Lime and hit the road. All things considered - construction, price, powerband and noise level - the best combination is the poned cylinder, milled head, and Scorecard: Modified RZ350. non-U.S.: 12.75 sec. @ 104.89 mph. Stock U.$. RZ350 with emissions junk: 13.57 sec. @ 97.44 mph. Euro pipes with European-spec jetting and the airbox and filter in place. Discounting noise, the best combination is all of the above with Toomey pipes. Those changes make the RZ350 an exciting, quick, wheelstanding roadster with the power of a 650 and none of the bulk. And that's worth a few grams of extra hydrocarbons noating around the atmosphere. • Best passes Stock RZ350 (new) 13.20 sec. @ 99.00 mph Stock RZ350 (2000 miles) 13.57 sec. @ 97.44 mph Stock RZ350. rejetted. Toomey pipes 12.61 sec. @ 105.50 mph Stock RZ350. rejetted. RSC pipes 12.57 sec. @ 106.25 mph Spec II RZ350. Spec II pipes 26 12.69 sec. @ 104.40 mph Modified RZ350. non-U.S. pipes Modified RZ350. Toomey pipes Modified RZ350. Spec II pipes 12.75 sec. @ 104.89 mph 12.20 sec. @ 111.38 mph 12.54 sec. @ 106.12 mph Spec II RZ350: 12.69 sec. @ 104.40 mph.