This all started because Allen Clarkson couldn't keep up with Ute.
Allen rides a '92 K75, Ute rides a '95 R100 Mystic.
Allen's K75 had been modified with the 'go-fast' options of a
K&N Filter-Charger airfilter, a high-pressure fuel-regulator (FPR) and a StainTune
exhaust. In desperation, he'd asked the assistance of myself and Brian Curry in figuring
out what was wrong with his K75.
Allen came to Sun Cycle (Mansquan NJ) www.suncycle.com where the owner, Frank Armadruto
offered us the use of his dyno, and his expert help in doing the dyno runs.
We tried several things - we had 2 spare FI computers, we swapped
them - no change. We had 2 spare Air-Flow-Meters, we swapped them - no change. We had stock and
K&N filters, we swapped them - no change. We did the usual K bike free-power trick of
advancing the ignition timing to 33 degrees (see the K-tech-FAQs at http:/www.ibmwr.org)
Finally in desperation we swapped the StainTune exhaust for a stock
K75 system. The results were dramatic:
Stock Exhaust vs StainTune - 1992 K75 - 4th gear 'roll-on'
At this point - Allen was happy, and we ran out of dyno
time, so Allen went home with the stock exhaust, and the advanced timing, a stock
air-filter and the high-pressure-fuel-regulator still installed.
Brian and I thought this must be a fluke - a defective
exhaust, and we wouldn't publish this info until we could confirm it.
We got the confirmation recently. Sun Cycle's owner had
another K75 in for service - it had a StainTune system on it that the previous owner of
the bike had installed. Luckily - the previous owner gave the new owner the stock system.
Frank decided while he had the bike in - to give the
owner some free dyno time - and try swapping the exhausts. Once again, the results are
Stock Exhaust vs StainTune - 1992 K75 - 4th gear
Different bike, different StainTune exhaust system,
different owner - but the same results.
We'll let the facts speak for themselves. The
StainTune is prettier than the stock system and is probably lighter (we didn't
Don Eilenberger, Brian Curry
FOOTNOTE: We also did a test of a
stock air-filter with 50% of the filter area blocked by SaranWrap[tm] - it was a
used stock paper filter. 50% blockage had no effect on the power the
engine produced. We also ran tests of the K&N vs stock and the K&N vs no
filter at all. Power remained the same. Any claims K&N make as to improving
power must not apply to K bikes (the same results were found on K100 tests).