SCOTT GUTHRIE REMEMBERS:
50 Years at Bonneville
Chapter #24?
?That?s just Scott. He?s always confident.
Frequently mistaken; but always confident!? Waiting for the record runs to start at about 8:00 on a cool, clear morning, I felt quite confident.
First thing Monday morning, after others ran for their records, I had a disastrously slow north-bound record run into a strong headwind. With my tach still MIA, I had no clue on RPM. The speed was a horrible 145.690, off by 20 mph, which was more than the headwind speed.
I suspected that the headwind had slowed me enough that the engine had fallen back below the power band, but I was unaware of the speed loss due to not being able to measure the engine RPM. IF I had known the RPM was down, I could have shifted down into 3rd gear, and accelerated back up to a competitive speed.
No tach = no information.
I had planned for this sort of wind situation when I was building the gearbox. Harley offered a number of different ratios for EACH of the three lower speeds in my racing transmission. Not particularly needing a quick start, I went with a very close set of gear ratios. First gear was an astounding 1.98 to 1, meaning the bike should go at least 50% of top speed in 1st gear; say almost 90mph. It would just take a while to get to 2nd gear.
I just needed a working tach, and I had no spare. Running the rest of the week without a tachometer might be an effort of supreme futility!
My third gear was a VERY unusual 1.08 to 1 ratio; with top gear being direct drive at 1 to 1. In that way, shifting from 3rd up to 4th at about 6,000rpm would only drop the engine back to maybe 5,500rpm - That would allow me to gear for a headwind, and run easily, while still in the power band, in 3rd gear.
With no tachometer, I had to base my shift points on ?feel? and ?sound,? just like the old timers? I wasn?t sure how well I could do something so new to me while actually racing.
With a tail wind on the way home, I could click it into high, and the tailwind would not push the engine past the red line. With no working tach, I was clueless. On the return run an hour later, with NO tailwind, I posted a 156.666mph.
MUCH better, but NO RECORD.
I started wondering if my engine was ?going away? (starting to fail)??again.
Tuesday qualifying at 7:30 am was in humid 76 degree air. If this was the weather page, it would say ?pleasant? over the salt flats.
A 10mph tail wind pushed me hard from the start, but I was unable to break 160mph; the slip showed 159.29mph at tire-spinning 5,825 rpm. Suddenly the tach was working again ? British technology?.
A serious young racing couple from Denver, Bill and Sharon Vickery, both set records riding Yamaha production road race bikes. Sharon nailed a 250cc record up to 141mph. A very significant number in 1974. That record still stands with the AMA ? almost 50 years later.
Sport Rider photo. Yamaha TZ250 of 1973 ? the only year of
Water cooling and drum front brake. Typical of what Sharon Vickery might have ridden; she and husband Bill were Yamaha dealers in Colorado.Sharon?s husband Bill Vickery rode a very modified Yamaha TZ750 to a record 191mph. Bill went deep into the mid 190?s on qualifying runs, but just missed a time over 200mph. Maybe because he closed off the front of the fairing to save air drag, the engine was overheating. This Vickery record would stand for years, and was substantially faster than his friend Don Vesco of el Cajon CA, who could only muster a 178 mph record?.
I had seen the future of Bonneville, and was too busy to pay attention at that time. I would suffer for that !
Chatting with Vasco years later ? shortly before his death ? Don revealed that he had never earned a 200mph time slip riding a sit-on bike. Remarkable for a man who had held both the motorcycle AND the wheel-driven car outright records. I offered rides on one of my bikes, but somehow we never could make it happen.
Scott Guthrie photo. Bike from Scott Guthrie Collection. Stock Yamaha TZ750 1974 ? Typical of what dealer Bill Vickery could have purchased for $3,495 new from the Factory. Sharon?s husband Bill Vickery rode a very modified Yamaha TZ750 to a record 191mph. Bill went deep into the mid 190?s on qualifying runs, but just missed a time over 200mph. Maybe because he closed off the front of the fairing to save air drag, the engine was overheating. This Vickery record would stand for years, and was substantially faster than his friend Don Vesco of el Cajon CA, who could only muster a 178 mph record?.
If I had not been partially deafened by my loud pipes,
I would surely have heard banjo music again.
We made three more attempts to qualify on the Harley, but with no success; our speeds quickly dropped down to 150mph, 140mph and finally 124mph, so I knew there was no hope, And yes, I knew that in 1975, this sounds JUST like the problems I had in 1974. BUT, this year we were not chasing multiple records, and the energy to work day AND night had gone out of me. Especially so since I knew that, number one, we were NOT going to go fast enough to set more than one record, and that number two, we would NOT find a satisfactory fix at Bonneville.
All ten(10) of my time slips had been signed by Pat Walkey.
On the bright side, not only was I faster than ANY bicycle of the time, I was almost as fast as Mike Corbin?s ?Run Silent Run Fast? 165 mph on a battery operated motorcycle.
Mike Corbin?s astounding 165.367 mph record of 1974 stood for decades as the SCTA/AMA best record speed for an electric motorcycle. After visiting with friends, we were off for home in North Florida.
SO: WHAT ABOUT THE CYLINDERS AND RINGS?
A later autopsy of the after-market aluminum engine cylinders ? which were cast of then-unobtainium KO1 silver , copper and other metal alloys - showed that the cylinder had probably not been properly ?seasoned? after casting. When I raced the bike HARD for the first few days, the iron bores gradually went ?square? at the four head-bolt locations, but only when up to operating temperature. Thermal loads were distorted the casting.
After running the engine to failure several times, there had been enough heat to permanently season the bores in the SQUARE position. The SAME THING happened again in 1975, also with new cylinders.
Photo - Wonderful idea, but there may have been a design problem also involved, since after running the bore(s) were NOT round. Thereafter, every overbore resulted in a VERY round hole - IF I torqued these plates down with proper torque before boring., Photo - I made ?torque plates? by machining some one-inch thick 6061-T6 aluminum alloy. IF I torqued these plates down with proper torque before boring, cylinders worked OKI just had to run EACH cylinder hard enough distort the bore in the first place.
The cylinder manufacturer was unfamiliar with the problems - and was very helpful - but had no solution. We speculated that even though they held up well on the street ? and at the drags with big loads of nitro - they never got as hot as at Bonneville.
Once again, the ?great white dyno? may have had more questions than answers.
OK - what was the deal with the rings ?
When the hot cylinder bores went square, the round rings were distorted trying to fit against the square bore. The hard chrome friction surface, which is hard and low friction but NOT ductile or very malleable, started breaking off. The continued running with the square bore broke off more and more chrome as the rings rotated around the pistons.
Gradually some of the hard chrome became embedded in the iron liner, and acted like diamond sandpaper ? killing every new ring set. The honing smoothed the scratched bores, but did not go deep enough into the liner to remove all the chrome So: the rings continued to die.
On the bright side, I had learned a lot more about racing at Bonneville, and the 164.83mph was my lifetime best ! AND, the three of the four records we set in 1974 still stood in the record book.
But next year, I would be kicked to
the curb.....
A NEW star would be born !
PHOTOS: In the original articles, lovingly published by Wendy at the BONNEVILLE RACING NEWS, there were PICTURES !...It is a little too cumbersome for me with my 75 year old pre digital brain to post those here since it involves photobucket and things like that. IF you go to my facebook account, the pictures are attached to THAT version of these articles..........https://www.facebook.com/scott.guthrie.3154.........