Cycle News - Archive Issues - 1980's

a: ~ ~ w ~ ..J « 0. .... ~' i2 >- CD Vl 0 .... 0 :I: 0. "o:::l"4 00 ~ 1""""4 ~ ~ 1""""4 l-o Q.) ..0 8 .... Q.) 0.. Q.) F-1 pipes are made by FPP for F-1. with spun aluminum silencers. The head-pipe paint turned silver-gray and rubbed off after a few passes. CJ'J Let's make RZ350 power! or, In Search of the-Socially Reprehensible By John Ulrich The last time we removed an RZ350's catalytic-converter-equipped exhaust system in favor of racing pipes (Cycle News, June 20) we learned several things. 1. An RZ350 fitted with said racing pipes is faster than an RZ350 with stock U.S.market pipes; 2. An RZ350 with a milled head and porting and 12 Canadian-market pipes or racing pipes is faster than a stock RZ350; 3. Advocating the removal of emissions control equipment in favor of gaining horsepower upsets some people. Our favorite letter on the subject came from a fellow who labelled our actions "socially reprehensible" and argued that we should comply with emissions standards simply because that's the law of the land. "Law of t.he land" arguments are the refuge of those who cannot think; if every American in history accepted such arguments, this -country would still be a British colony and we'd probably all be riding Triumphs or maybe changing exhaust systems on BSA Bantams. A little law-breaking in moderation isn't necessarily harmful; a good example is breaking the 55-mph spt'ed limit when doing so does not compromise road safety and when a Highway Patrol car isn't in sight. Another good example is trading pounds of ugly, horsepower-restrict- ing catalytic converter for wheel ieproducing horsepower. Which is exactly what this story is aU about. It seems that after we published the results of our first dragstrip excursion with an RZ350, pipe manufacturers raised a hue and cry, mainly pipe manufacturers whose products were not included in our first test session. So it was that we returned to the dragstrip with our RZ350, which, by this time, had accumulated over 3000 street and racetrack miles. We brought with usa set of Toomey pipes to use for baseline comparison - we had run Toomey pipes during thefirsttest session and ran 12.61 sec. @ 105.50 mph with rejetted carburetors. (We had run 12.57 sec. @ 106.25 with RSC Noguchi pipes, but in subsequent riding a silencer broke off one of the RSC pipes). Along with the Toomey pipes, we brought sets of RSC Allspeed, Bassani, Factory Pipe Products (FPP) and F-I pipes. There are two things to be remembered when looking at dragstrip results. The first is that atmospheric conditions count, so one day at the drags isn't necessarily the same as another day at the drags, and results can vary accordingly. The second is that the closest indication of horsepower is terminal speed. We started out by running the bike with Toomey pipes and #370 main jets (#230 are stock) with the airbox boots removed; That's the jetting Stuart "I:oomey recommends. The RZ's best pass was 12.42 sec. @ 106.25 mph, beller than the 12.61 sec. @ 105.50 mph the bike turned with the same jetting and pipes the last time we took it to the drags. Next weran theF-1 pipes with the same jetting, #370 mains; the bike's best pass was 12.75sec.@104.16mph. That's significantly slower than the bike went with the Toomey pipes. It occurred to us that maybe the F-I pipes would work better with stoc" jets, so we installed the stock jets and the airbox boots. In that configuration, with the F-I pipes, the best the RZ turned was 13.06 sec. @ 102.85 mph. Next were the RSC Allspeed pipes, which, according to RSC, are made to be run with stock jets. That's how we ran them, and the RZ turned 12.90 sec..@ 102.73 mph. Without changing jets, we installed Bassani pipes, and the RZ turned 12.70 sec. @ 105.14 mph. With stock jets and FPP pipes, the 350 turned 12.67 sec. @ 105.26 mph. We then installed the Toomey pipes - still with stock jets - and here's where everything got complicated. There were two people at the drags besides me; Doug van Almelo, a Yamaha mechanic, to help with . changing pipes and jets; and Cycle News Associate Editor Kit Palmer, to run the clocks. Both wrote down the results of each pass and the modifications made between sets of passes. The notes each took agree up to the last set of runs, with the Toomey pipes. The disagree- ment concerns just when the RZ350 was rej elled. The idea was to run the Toomey pipes with stock jets - to compare it to the other pipes - and then run it with the big jets to compare its endof-day times with its beginning-of-day times, a handy way to make sure the. bike hadn't slowed down during the day's runs. (The end of our dragstrip "day," or test session, happened to be about 2;00 p.m.) The notes agree concerning the first three passes for the Toomey pipes with stock jets - the best being 12.96 sec. @ 105.01 mph. The disagreement - discovered after we had left the track - came over whether or not the carbs were rejetted after three runs or five runs. Palmer's notes said five runs, which would give the Toomey pipes a best stock-jet pass of 12.68sec.@I06.25mph.VanAlmelo's notes said the bike was rejelled after three passes, giving it a best stock-jet pass of 12.96 sec. @ 105.01 mph. Both agreed the best pass of the set - regardless of whether the rejeuing occurred on third or fifth pass - was the seventh pass, 12.48 sec. @ 106.88 mph, comparing well to the first pass oftheday - 12.42 sec.@ 106.25 mph made with the Toomey pipes and rejetted carbs - and showing that the bike hadn't been damaged during the day's runs. Looking at terminal speeds, it's likely that the bike was rejetted after three runs, and that the best pass wi th Toomey pipes and stock jets was 12.96 sec. @ 105.01 mph. (That's slowe.r than the results we got with stock jetting and Toomey pipes the first time we went to the drags, 12.67 sec. @ 104.89 mph.) And as we argued the point, another problem surfaced: Toomey and FPP both recommend #370 main jets and advise against running the stock #230

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