Product: JRF Torque Controller

Why your two-stroke dirt bike stands to benefit big-time by bolting on what is, in effect, a damper for your engine’s power-valve mechanism.

WHAT IS IT?

• Designed by the late, great doyen of the Australian off-road race scene, John Hall, the JRF Torque Controller is a bolt-on damper that helps control the opening rate of a two-stroke’s power-valve. It’s designed specifically to tame the aggressive hit of a two-stroke engine; to generate smoother and more usable power, better rear wheel traction, and less rider fatigue.
• It weighs 400g and is made from black-anodised billet alloy.
• The product is available for KTM’s 2009-2016 SX and EXCs, Husaberg’s 2011-2014 TEs, and Husqvarna’s 2014-2016 TEs.

HOW TRANSMOTO RATED IT (FROM ISSUE #49)

Modern-day two-strokes’ power tends to be broader and torquier than in the past, but because premix burners remain more aggressive than their four-stroke counterparts, any bolt-on mod that gives you the option of more tractable power is a good thing. While most late-model two-strokes come with some power-valve adjustability (varying springs and/or preload), their adjustments are fairly coarse. The JRF Torque Controller, however, is unique in that its adjustments are made without tools – via an eight-setting dial that sits atop the unit.

As the JRF only dampens the power-valve’s mechanism (rather than giving you settings either side of standard), we found that it works best when used in conjunction with the most aggressive (softest) power-valve spring in the KTM/Husaberg/Husqvarna. This combo gives you a broader range of power delivery options, with setting 3 or 4 roughly equating to the standard spring. Anything beyond setting 4, however, slows the opening of the power-valve noticeably and generates smoother, more linear power. That makes the bike much more rideable in slick terrain, and turn the dial to adjust the power-valve setting is way quicker and easier than replacing the springs in the power-valve mechanism.

The JRF is quick and easy to install (once the expansion chamber and power-valve cover is removed) and has a viewing window to double-check the damping arm is working properly. Like any oil-damped mechanism, it does require servicing (roughly every 12 months), but for less than $450, it’s a very cost-effective bolt-on to make your two-stroke’s power much, much more versatile.

PRICE

$449 AUD, available from www.tmparts.com.au/JRF

BIRTH OF THE JRF TORQUE CONTROLLER

JRF’s Malcolm Hall offers this insight into the product’s inception and subsequent development for a wider range of two-stroke dirt bikes…

“The concept goes back a few years to when my father, John Hall, was alive. He was passionate about motorbikes and in particular TM Motorcycles, which he and I used to import for over 20 years through Cross Country Action. It was when dad was in Europe helping out one of our young enduro stars called Jake Stapleton, that the idea came to him. Jake’s TM 250cc two-stroke had a shit-load of power, but it came on too hard because of the way the power-valve worked. Dad decided there must be a way to dampen that aggressive hit, so when he came back to Australia he decided to start work on a hydraulic power-valve dampener, and called it the JRF Torque Controller.

“It basically works exactly the same as a hydraulic steering dampener, except on the bike’s power-valve mechanism. After selling a lot of the JRFs to TM customers all over the world, many people asked us why we didn’t also make the product to suit the most popular two-strokes on the market, KTM. So I did. We had to completely change the mould for the product’s body (so that it bolted snugly onto the KTM’s engine), but the principle and internal workings remained exactly the same.

“The JRF changes the way to power comes on. In short, it smooths out the power delivery, which helps improve rear wheel traction and reduced rider fatigue. In fact, one happy customer went so far as saying, ‘This thing actually makes a two-stroke into a four-stroke!’

“Transmoto’s vastly experienced test rider and multiple ISDE gold medallist, Damian Smith, tested the JRF Torque Controller on a 2015 Husky TE250 and came away very impressed with how much more user-friendly the bike’s power delivery became in slick conditions with the JRF fitted. We sold one recently to a guy in Poland for his KTM 300EXC, and he was similarly happy: ‘JRF works perfectly. After testing it all day, I can confirm it is a really clever and effective device as it can be quickly adjusted depending on where I ride the bike – for a faster MX track, I set the dial on #1, but for wet conditions and hillclimbs, the #5 setting makes the power so much smoother and easier to use’.”

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