SportGear Steps Up For
Big Performance Boost
 

 

 

 

Johnson Engineering
100 Blake Road
Denver, IA 50622
(319)984-9298
(319)984-9299 fax
info@twistgear.net

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May 15, 2003

See New Speedometer Installation Footnote

SportGear Helical Performance System

SportGear bw SportGear kit

We haven't left Sportster riders or Buellers out of our helical family of V-twin close ratio performance systems. Johnson Engineering continues to revolutionize the art of transmission technology with SportGear, the fifth-gear/main gear helical replacement assembly for 1991 and up Buell (tube frame trapdoor models only) and Sportster five-speed transmissions. Our exciting new close ratio replacement set unites the proven characteristics of helical design with the power and handling potential of unit construction v-twins. (more details)

Gearing Down For Top End Performance

Want to steamroll the competition and enjoy a more comfortable ride while you're doing it? SportGear’s the quickest way to unleash the full potential of your Buell or Sportster, without sacrificing around town performance. Designed specifically to improve all around performance for sport riders, the computer generated helical tooth design delivers much quicker acceleration than stock, something that will appeal especially to 883 riders.

How do we do it? The cornerstone of the SportGear helical performance system is our unitized 5th gear/countershaft combination. Our 5th gear is a 22t helical that meshes seamlessly with our 42t helical main gear, delivering an ouput ratio of 1.91:1, which is nearly 14% more reduction than the stock ratio of 1.68:1. (XLs, at 1.73:1, get a little over 10% reduction, similiar to our Big Twin TwistGear helical performance system.)

Cruising Made Comfortable

For peak cruising performance we recommend a 29/55 pulley setup to lower engine speed on those long interstate romps, while simultaneously delivering the extra leg needed to let that engine wind out on the top end. (The 29/55 swap is more for Buells and 1200s, although 883s might benefit from a 55t rear pulley for lower rpm and still have acceptable acceleration.) Result? Comfortable cruising with an appetite for the Autobahn.

Buell chart
The chart above demonstrates the significant advantage SportGear has over stock gearing throughout the shifting range. Take a look at that top end, which is achieved with the final drive ratio indicated.

Above, we compare a stock Buell drivetrain to a SportGear modification, including the recommended 29/55 pulley setup. The results are obvious; a near identical overlay at shift points in 1st through 4th, meaning no loss of acceleration, while top end at 7200 rpm improves dramatically over the stock configuration (rev shift points in blue). For more info, refer to our PDF SportGear worksheet.

Because final drive remains 1:1, the advantage of SportGear technology comes from applying the close ratio aspect of 1st through 4th combined with the taller gearing required for top end improvement with no loss of acceleration.

Incorporating all the proven technology of TwistGear in an optimized sport performance package, SportGear also includes our exclusive four-point caged ball bearing, improved triple lip oil seal, and chamfered spacer improvements for long life and reliable operation.

Behind Helical Close Ratio Technology

With a 29/55 sprocket setup (recommended for all around performance), SportGear delivers 13.6% more overall gear reduction than the stock 27/61 configuration. Fifth gear revs are reduced over 16%, yet only a negligible 4.6% in 1st - 4th gears. The result is a taller overall gear ratio that still retains near stock acceleration through the first four gears, and a linear acceleration curve in fifth. It’s the same effect as an overdrive, yet with all the benefits of a direct drive, and at a fraction of the cost.

More Comfortable Highway Cruising

sportgear asm With the recommended 29/55 sprocket setup, engine speed is reduced about 470 rpm at 60 mph in 5th gear while keeping the gear reduction in 1st-4th gears close to original. This provides four narrow ratios for street performance, with a highway cruising gear that delivers about 30 mph more top end before hitting the rev limiter.

Help For Underpowered 883s

SportGear is the best improvement you can make for an economical, efficient solution to quicker acceleration, a quick and elegant route to improving around town riding and highway cruising at a fraction of the cost of adding horsepower, especially with the recommended 27/55 pulley swap.

You'll notice better comfort and performance immediately thanks to SportGear's computer generated ratio reduction, which translates into closer gearing and better pulling coming away from the light or manuvering through traffic.

Improved Sealing Means No More Oiling

SG cross sectionHidden improvements include a lengthened main gear with an integral retainer snap ring to keep the oil seal from falling out of the bore (a common problem with OEM and other aftermarket parts) while also preventing the shell bearing from moving out of the bore. Note also the beefier caged roller bearing at left, in place of the drawn cup that comes stock. Much tougher, and also retained by snap rings to keep everything neat and tidy.

In addition, the trap door bearing retention screw on the counter shaft (left side of illustration, below) has been strengthed to prevent screw loosening. Torque it down, and it stays tight! The engineering drawing below shows how our massive improved fastener has the bite and the capacity for proper retention, mile after mile.

SG cross sectionSportGear benefits include smoother shifting, a quieter transmission, less vibration - especially with solid mount transmissions - and lower cruising rpm, all in a super quick acceleration package especially designed for the Harley sport rider. And with our superior oil sealing and spacer technology, there's less down time for interval maintainance, which means more riding without leaking.

Electronic Speedometer Installation Notes

At present we're tooling a .086" spacer for the speedo pickup on Sportsters and Buells equipped with electronic speedometers. In rare cases, the end of the sensor may contact the main gear od, with obvious results. Depending on your final ratios, you will probably need to recalibrate.

Get More Info In The Library

Put all this and more info, including OEM replacement part numbers, on your own computer. Check out our new SportGear PDF documents for download. Also check out our SportGear Tables.pdf, for pulley P/Ns needed for a swap.

SportGear™ and TwistGear® are trademarks of Johnson Engineering, Inc. Buell™, Dyna™, and Sportster™ are trademarks of the Harley-Davidson Motor Company. No affiliation with the Harley-Davidson Motor Company is implied or inferred.