Crankshafts
We used modified crankshafts in Yvon's bikes, from
stock as follows ("stock" refers to stock H1/H2 street bike parts):
H1R: standard flywheels, slotted stock rods, stock crankpins, stock thrust
washers, silver plated rod bearing cages and stock rod rollers (the silver
plating was to help NOT seize the rod bearings to the cages), oil receivers in
place (remember, we used a combination of oil injection locked in the idle
position for the left main and rod centrifugal "sling", with a 30:1 premix in
the fuel tank, cases undrilled for the cylinder oiling passages, stock oil lines
washers and banjo bolts), two outer seals back to back in the centers, roller
main bearings that were set in the cases with a number of locator rings, and
these main roller main bearings had orange Teflon outer filled areas, to keep
them from spinning in the cases, and stock 16mm wrist pins and upper rod
bearings.
The two outer seals back to back was because the early street H1's used a
proprietary center main seal, didn't actually touch the crank until crankcase
pressure pushed the lips of the seal down on the seal collars. Later H1R cranks
used stock center lab seals, as they were redesigned in 1970 to be positive
pressure, spring loaded against the seal collars.
Yvon spun these engines to 11,700 rpm, Erv had his win every AMA Junior class
race he and John Greene raced in.
One very special crankshaft was produced, was worth a few mph and some small lap
time improvement, was configured with flywheels cut away, as in the stock H2 and
H2R cranks. It is now outside, in its factory package here with me. Yvon won
Talladega with this very crankshaft in 1971,
H2R: stock flywheels, oil receivers in place, same reason as above, same oiling
methods, stock rods with slots cut into them (as later H2 stock rods are
slotted), same silver plated rod bearing cages, stock rod bearing rollers, stock
thrust washers, stock crank pins, ball bearings for the mains, with the orange
Teflon inserts for spin issues, this way, the stock single locator in the cases
would hold the crank side to side, with less rolling restriction than the H1R
type roller bearings, center seals were stock H2 stre4etbike, as they were
positive pressure type, held the seal lips hard to the seal collars, stock small
end bearings for the stock H2 16mm pins, which were also stock H2 parts.
We ran these engines to 11,000, and no more, and only on short tracks that only
needed acceleration, not top speed for a long time. Long tracks we ran them down
to 10,500 or so.
Note on H2R pistons and pins. Early engines used an ART forged piston. These
pistons had a few issues, as in flexing front to rear, which distorted them into
binding the 16mm wrist pins, flexing them and causing the pistons to fail in the
pin bosses, breaking the pistons, and also, intake skirts falling into the
intake ports, making the classic "smile" on the inlet skirt. One "fix" from the
factory in early 1973, was to use a forged piston with 18mm pin and special
upper rod bearing. This had little positive effect on the piston breaking
issues, and were solved only by new ART centrifugal spin cast 16mm pistons we
used from the Easter Match Races onwards. Yvon actually blew a rod through the
cases after one of the last forged pistons let go, lighting the fuel and trans
oil up, causing us to refer to the bike as "The Imola Fire Bomb". The cast ART
specials were really leaps and bounds better than the ART forgings ever were.
The only person to tear up H2R rods/pistons after that, that used Kawasaki
parts, was Erv Kanemoto on the Nixon bikes. At Atlanta, Erv was so upset about
the engine failures on Gary's bike, he had a constant nose bleed as he and Gary
went through two of his engines, pistons broke, rods through the cases. Finally,
Steve and I put one of our/Yvon's spare bullets in his chassis for Erv/Gary for
the race, as he sat, nose bleeding. Poor Erv, he really had one bad weekend on
that one. Come to find that Erv was "porting" the insides of the pistons with
his die grinder, trying to lighten them. They were already a bunch lighter than
stock pistons. They were just plain too weak to survive after Erv lightened
them.
Crankshaft life was about 1,500 racing miles for the H1R's, 1,000 for the H2R,
rod bearings being the questionable parts for longevity.
As an aside, the Yamahas I worked on and built for Al Salaverria in 1990 had
great crankshaft life. Two sets came with the bike, one in the engine, one set
spare. After going through them from new, they'd go half a year of full AMA
250cc nationals, testing and AFM races, each set.