JS Motorsport
 
 
motorcycle
HIGH-PERFORMANCE
PARTS
FOR NORTON TWINS
JS Motorsport
4480 North Academy Avenue
Sanger, CA 93657
Phone/Fax: 559 875 0659
Email: jim@jsmotorsport.com
JS Motorsport Photo Gallery

Gary Thwaites tucked in and leading at Pembery. Gary won all seven national 1300cc classic races for the 2012 UK championship on Dave Watson's 1007cc Seeley with JSM Motorsport lightweight pistons, longer rods and stage 3 cam kit with lightweight radiused lifters. "The engine is much smoother and power up...we are well happy with the bike and all your gear that is inside the engine...Gary rode the big norton in two Crmc meetings in 2013 at Cadwell Park and Donington and won all his five races. Gordon Humphreys (tuner)."

"At the CRMC Croft event May 7, 2016 and the Sunday June 19, 2016 Bob Mcintyre event, Gary won all six races in his class and made fastest laps in Classic. Gary Watson (owner)."

This motor has over 40 races on it with the same JSM parts, The rings were replaced. The bike continues its winning streak in 2017


David Blankens immaculate 750 with lightweight JSM pistons/conrods. "Thank you Jim for all your help... the bike is running awesome and sounds great, and very pleased with your Norton products. Cheers" Dave from Australia
Maria Costello winning races in Bears class at Daytona and Barber 2011 on the Dan Rose 750 Seeley with JSM lightweight pistons, longer rods, stage 2 radius cam with lightweight lifters and beehive valve springs. This is one of the fastest long stroke 750s on the tracks. Photo courtesy of Lisa Theobald.

Doug MacRae scores a couple wins at Mid Ohio in July 2015 on his short stroke with JSM lightweight domed pistons, Longer Carrillo short stroke rods, JS2 radius cam, beehive valve springs. Other trick componets include FA bathub combustion chamber designed by Herb Becker, 5 speed Nourish/Triumph gearbox.

Click HERE to view the onboard video.


Randy Johnson's land speed record breaker for SCTA 750cc production pushrod motors on gasoline (126mph at Bonneville in 2012 with a best one way speed of 128 mph). This bike has all the JSM goodies including Ultra high compression domed lightweight pistons, gapless rings, longer rods, stage 2 cam with lightweight lifters, beehive valve springs and black diamond valves. "The engine really wants to run, it picked up 9 mph between the 2 and 3 mile traps... Thanks for the great parts and the advice.  It's a great motor," Randy. (Builder is Steve Adkins at Preservation Cycle).


Proud owner Giacomo Cavecchi, from Italy, with his beautiful 850 Commando
running JS Motorsport lightweight pistons & rods.

The first bike to win a race with our lightweight pistons & longer rods. Owner Herbert Toscany

Lightweight 850 JSM pistons and longer rods, JS stage 1 cam, Beehive spring and valve kit. "The bike is now SO smooth everywhere, I am really surprised...before it felt agricultural/Harley-ish... it now feels tight and zippy, finely honed, almost modern in some ways. Hard to explain really, but good!" Nigel Waring

I am going into my 4th season of racing with 2 bikes that use your long rods and short pistons. I have not opened any of the engines again since the rebuild with your parts 4 years ago.  Everything is still going strong. No need for replacement or service. I am totally satisfied. Herbert Toscany

"Jim, just a quick note of thanks. Took the Seeley Norton racing this weekend (April 2010). The balance was absolutely spot on just fitting your pistons and rods. The motor starts well and pulls like a train all the way up the revs with no perceptable vibes. It was a real boneshaker before! I've had folks wanting to know what has been done to the motor to make it so smooth and tractable. Thanks again Jim." Norman (Scotland UK).


"After a shake down at Pacific Raceway in Seattle I got the bike down to Willow Springs for the AHRMA Nationals (May 2010). Took 2nd in the Bears class. Vibration was not a factor (JSM pistons & rods), and the bike pulled strong, with a noticeable increase in power (stage 2 cam kit & lightweight lifters). I'm pleased thus far." Jesse Seary (British Columbia Canada)

Here's where the lightweight pistons started - Jim Schmidt at Willow Springs raceway in the mid 1980s. Pushing his Norton monoshock 850 to the max.

The Dan Rose 750 Seeley racer full of JSM components - lightweight pistons, longer rods, .003 head gasket ring, stage 2 radius cam with lightweight lifters and beehive valve springs. Won its class at Daytona in 2011.


Jordan Baber riding Kelly George's successful 750 flattracker with lightweight JSM pistons/conrods and JS stage 2 cam.


"On the track with my Seeley Norton with JSM pistons and conrods inside. Very good engine, very powerful on the mid range. I left a lot of other Nortons behind on the straights and out of turns." Lucas


Enjoying his first ride down the Australian coastline after installing the smooth running lightweight pistons & longer rods - Ian Palmer.


920cc Seeley with JSM lightweight pistons, longer bushless rods, stage 2 cam, lightweight lifters.
In 2010 it tied exactly with the 1000cc pushrod fuel, unstreamlined, Bonneville land speed record.
In 2011 it achieved 155+ HP at the crankshaft on Nitrous.
"Jim, I'm really impressed with your products, it runs SO MUCH SMOOTHER with the lightweight pistons." Fred Eiker


"Hi Jim, I've finished my bike and it runs and sounds great. Your camshaft and lightweight lifters seem to make the bike feel different in a very good way. It has less vibrations and is quieter somehow. It feels like it has more accurate combustion too, I suppose this is due to the curved lifters. Thank you for selling me the kit. I am so pleased with it I put your stickers on the sidepanels." Petter Olden

Jim Schmidts wideline Atlas test bike with lightweight pistons, JS 0 cam kit, JSM carbs, Beehive springs, Hunt magneto and all the rest of our trick components. Good for roll on wheelies and 80mph cruize (4:1 gearing). Less than 1% leakdown with 30,000 miles on the rings and pistons.

"The slower piston speed (at TDC) combined with the light weight certainly makes for a lot less stress and vibration", Jim Cossin's (AKA Commando Garden) is enjoying his 750 with JS lightweight pistons, longer rods and gapless rings. Crank rebalanced to 58%.

Paul Coughlan's race 850 Commando in Australia with lightweight pistons/longer rods, JS stage 2 lightweight lifter cam kit, beehive valve springs.

Stunning featherbed 850 owned by celebrity song writer Billy Joel. Sporting JSM carbs.

Canadian Michael Mackin's '69 Commando, restored to perfection by Garrie Cook, complete with JS Motorsport pistons/rods. "Runs very smooth and quiet".

Bruno Waltersbacher's 850 Seeley racer with JS lightweight HI comp pistons, longer rods, JS1 cam kit. Dynoed at 78 HP.
See a dyno run of early version of the motor HERE


Lars Poulsen's race ready Commando with JSM lightweight pistons and longer rods


"Jim, here's the pic of the long awaited finished bike.  Steve [big D cycle] said it's the smoothest 850 he's ridden.  It surprised Keith [big D cycle] when it did 60HP between five and six and a half grand at the rear wheel on the dyno and at 5K sounded like it shifted into a higher gear or someone turned on the nitrous!  Thank's for all the good products."  [JS lightweight pistons, longer rods, JSM carbs, stage one cam & lightweight lifters, beehive valve springs] Brad Baird

Ralph Coldwells 850 with lightweight JSM pistons/conrods and JSM carbs.

Mike Hamilton's 850 with lightweight JS pistons/conrods, JS Stage 2 radius cam kit, beehive spring & valve kit, turkite bushings, 63% crank balance. Showns 70+ HP on the dyno.

Stuart Metge's 500 dominator with ultralight JSM domed pistons/conrods, Stage 1 radius cam kit, beehive spring & valve kit. SS 650 head. Revvs freely to 8000RPM

Victor Vassella's 920 featherbed with lightweight JS pistons/longer conrods, 130+ on the straights

Yves Van Heer's perfect 850 Seely with JS lightweight pistons/longer rods, gapless rings, JS2 cam with lightweight lifters and custom billet 23 lb crank balanced at 65%. "The engine is working great, without vibes and when you reach 5.000 rpm you go amazingly fast to 6.500 rpm (62 BHP/5900 RPM at rear wheel). When I am on roads and I stay between 5.000 and 6.500 and go down or up in the gears at every turn it is a song of joy... The lightweight lifters and valves springs are also top of the game. I dont touch the engine since 10,000 kms and this never happends before. And believe me, I ride hard" Great work Jim


One of the fastest period roadracers in Australia with JS long rods and special lightweight 850cc 14:1 C.R. domed pistons for Methanol. JS big valves and Beehive springs. JS3 cam with lightweight lifters. Does 11+ sec in the 1/4 mile. Classic unlimited champion in 2017. Proud owner/rider - Garth Francis.

Side car belonging to Australian Garth Francis using JSM long rods and 850cc lightweight domed pistons on methanol.

Swedish racer Per Holmstrom on his 750 with bathtub combustion chambers, JSM high C.R. pistons/longer rods, beehive spring & valve kit, JS stage 3 cam.

German racer Bern Schaefer on his 850 with JSM high C.R. pistons/longer rods, beehive spring & valve kit, JS stage 2 cam. Motor revvs to an amazing 8400 producing 75 HP using 33mm keihin CRS carbs.

French racer Bruno Perlinski on his 750 short stroke with lightweight JSM domed pistons/longer rods, stage 3 cam, Beehive valve springs, rocker spindle covers

Perlinski's row of Seeleys. The bike in the foreground uses a 270 deg crank with JSM internals and is winning races in France with Steve and Bruno Perlinsky riding.

I placed 2nd in 1984 at the Laguna Seca 750 BOTT AMA National with this 750 slimline featherbed. Long homemade 35mm Guilotine slide carbs, Very fast. Fred Eiker and I traded 1st place every lap at this race. These were the days when we first started dragging our knees.


Mark Gunning's better than new 850 with CRS 33mm carburators.


Dennis Donahoe, winner of the 2015 pacific coast championship. This extraordinary Norton was built in 2010 and has 40 race events on the lightweight pistons/longer rods & JS2 cam. "The motor has had no issues and is still running strong".


Custom Commando racer I built for Rod Hurick in the 1980s. Box swingarm with eccentrics, Alloy oil tank, alloy engine cradle, Motor built to Axtell specs.


John Puhakka in Finland on his 750 Featherbed with JS lightweight domed pistons/longer rods, JS stage 2 cam, Beehive valve springs and big valves, Turcite fork bushings


Brian Coopers 8500RPM short stroke 500 domni with JS2 cam kit and beehive springs. "with your parts fitted for this years classic TT the bike flew with no problems".


Michael Panayi's featherbed from down under. "I currently have 2 race engines (750 & 920) that have your pistons and rods which have been winning plenty of races."


Andy's 750 shortstroke land speed racer with JS domed pistons and longer rods. JS2 cam, A solid 75 HP on the dyno. With a 920cc engine it showed 90 hp on the dyno and achieved an amazing 149mph at Loring Maine speed trails in 2017 with JS flat top pistons and longer rods. Herb Becker (tuner) on left.


Andy's land speed racer with 90 HP 920cc motor. It achieved an amazing 149mph at Loring Maine speed trails in 2017 with JS flat top pistons and longer rods. The fastest unstreamlined, naturally aspirated gas powered Norton on the planet.


Robert Hood and passenger Mark Thompson won the New Zealand Classic Motorcycle Racing Register (NZMCRR) Post Classic Sidecar Championship in 2013, 2014 and 2015. Lightweight 920cc JSM pistons and longer rods. Maney cases and Barrels. One piece crank by Graham Martin in NZ. 36 mm Dellorto’s. 11.5:1 compression on methanol. 70 ft lbs torque and 80 BHP at the back wheel. 97 races and counting on the same lightweight pistons and rings.


Les Clark's Seeley with JSM 33mm CRS Smoothbore carbs. "Pulls like a train."


"Hi Jim, I’m finally sending you those promised pics of my ’64 Atlas. She’s done 7,000 Km now. The engine has your lightweight pistons, Carrillo rods and complete Stage 1 cam kit. What can I say, the engine is unbelievable, makes the bike a joy to ride, and gives the later model Trumpy twins a serious run for the money."


"I've got a 750 Atlas with your long rods and lightweight pistons installed and your recommended balance factor.  Having undertaken a complete restoration on the bike...and am very happy with the vibration levels." Tom


Redento's perfectly restored 750 with JSM lightweight pistons/rods and Beehive valve spring kit. "The bike is working very well, very little vibration. Compliments, I am very satisfied."


"Hi Jim , I have just finished rebuilding my 71 Commando. We used your lightweight pistons, rods, lifters, street cam, beehive spring/valve kit and a set of your Keihin carbs. It starts first kick and idles well, those carbs are great." Gareth


Dave's Rickman sporting JSM 33mm Keihin CRS smoothbore carbs.


Jan's 850cc powered N15 with JSM lightweight pistons and longer rods running "very smooth".


Hot Combat with JSM performance parts and Gorgeous adornments.


Redento's Bonnie with JSM Lightweight bushless Carrillo rods, DLC pins and stock pistons. Rod weight is the same so rebalancing is unnecessary


John Pitchers 650 SS Domni racer with JSM parts.


Steve Adlem on his shortstroke with JSM bushless rods, high C.R. pistons, Beehive springs and black diamond valves.


920cc Featherbed with JS2 270 deg cam.


Ian Salters sidecar racers with JSM lightweight pistons and longer rods.


Mats Hall's 750 shortstroke placing 1st place in Swedish cup formula 750 in 2017 with JSM lightweight pistonsand longer rods, custom cam with JS2 exhaust and JS3 intake lobes.