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Trevitt's Blog: Can Two-Strokes Make a Comeback?

KTM and Husqvarna recently announced that they will be producing two fuel-injected two-stroke models for 2018, as part of their respective enduro lineups. (The Husqvarnas will be essentially rebadged KTMs, as are most of the company's models.) While most manufacturers, including KTM and Husqvarna, offer a range of two-stroke dirt bikes, there have been few two-stroke street bikes of any note since the demise of the Yamaha RZ350 in the mid-nineties. The KTM and Husqvarna announcements, even though covering enduro models, could be the beginning of a trend that sees two-strokes making a comeback in the on/off-road market, and perhaps eventually street bikes.

Two-strokes offer less weight, fewer moving parts, less friction and - of course - twice the number of power strokes than four-strokes, for substantially more performance in a given displacement. On the downside, however, emissions and fuel economy are significantly worse. There are two issues here: One is that in the two-stroke cycle, the transfer ports (that "transfer" the fuel/air mixture from the crankcase into the cylinder) are open at the same time as the exhaust port, and for a significant portion of the cycle. During this time, unburnt fuel can go directly out the exhaust, affecting emissions considerably. The second issue is that, because the fuel/air mixture in a conventional two-stroke passes through the crankcase, the lubricating oil for the big-end and main bearings ends up being burnt along with the fuel, also affecting emissions. The writing was on the wall for two-stroke street bikes in the early eighties, with increasingly strict emissions laws being more and more difficult for the manufacturers to comply with.

In the mid-nineties, Bimota manufactured the V-Due, a 500 cc two-stroke V-twin street bike. The V-Due worked around the emissions issues by using fuel injection and forced lubrication for the bottom end. Ideally, a two-stroke would use direct fuel injection, where fuel is injected into the combustion chamber (rather than the throttle body) after the exhaust port is closed, to minimize emissions. This technology has issues of its own, however, and the V-Due used transfer port injection. While not an optimum solution, in this setup only air goes through the throttle body, into the crankcase and up the transfer ports; the fuel is finally injected in the transfer ports, where it can't pick up the lubricating oil. As well, the exhaust port can be almost closed when the fuel is introduced, minimizing how much goes directly out the exhaust unburnt.

With a separate lubrication system for the V-Due's bottom end, and only air going through the crankcase, the amount of oil that made it to the combustion chamber was also minimized. While the bike did pass US emissions standards at the time, it had significant issues with rideability attributed to the fuel injection, and eventually the system was scrapped altogether in favour of carburetors. Even then the model had continuing issues, and was largely blamed for the company's bankruptcy.

While little was revealed in the KTM and Husqvarna press releases, the KTM version did indicate that the new bikes use transfer port injection, like the V-Due. Certainly the technology has progressed significantly since the V-Due's time, and KTM promises "a completely new experience in terms of power delivery and rideability." KTM, and other manufacturers, have surely been working on two-stroke fuel injection for some time, and the technology is very common in the marine and snowmobile market. If the new KTMs deliver on those promises of rideability and power delivery, it may open the floodgates for the other manufacturers to follow suit.

What will the holdup be for street bikes? The RZ350 and V-Due had a difficult time meeting the relatively relaxed emissions standards of their time, and the current Euro 4 standard is extremely difficult even for clean-burning four-strokes to meet. Load up a two-stroke with direct injection, an elaborate lubrication system, exhaust valves and other extras to meet today's standards, and cost, weight and complexity quickly approach the four-stroke realm. (Note on the image above all the extra equipment tacked onto the cylinder of the KTM engine.) Additionally, in the last 20 years since the V-Due, four-stroke technology has improved considerably and closed the gap to two-stroke performance.

The media launches of the new KTM and Husqvarna models are mid-May, at which time we'll know more about the technology used and if it could potentially be applied to street bikes. It may be wishful thinking on my part, but I don't think I'm alone in wondering how something like an up-to-date RZ500 would compare to a current four-stroke litrebike.

Friday, 07 April 2017 12:16 Published in Andrew Trevitt


Trevitt's Blog: Cornering ABS and using the rear brake

One rider aid that is available on an increasing number of new motorcycles is cornering ABS, sometimes incorporated into a stability control package. In its basic form, a cornering ABS function takes into account the motorcycle's lean angle to adjust brake pressure, increasing the ABS effectiveness beyond a simple straight-line stop. However, as I outlined in a previous Inside Motorcycles article ("Smarter ABS," Dec. 2015), these systems offer much more than just improved ABS function.

One basic handling characteristic of practically all motorcycles is the tendency to stand up when the front brake is applied in a corner. Due to the front-end geometry and the relationship between the front tire's contact patch and the steering axis, using the front brake when the motorcycle is leaned over causes the steering to turn further into the corner, inducing countersteer that stands the bike up and causes it to run wide. This, of course, is exactly what we don't want when we encounter a fallen tree limb or some similar hazard in the middle of the corner.

The various cornering ABS functions, sometimes part of a stability control or cornering management feature, counter this by sensing that the motorcycle's lean angle is decreasing as the front brake is applied, and transferring brake pressure from the front brake to the rear. This reduces the induced countersteer but retains overall braking pressure, so the motorcycle still brakes as the rider wants but doesn't stand up.

Noted tuner Kaz Yoshima uses the analogy of driving a car with a trailer when it comes to using a motorcycle's rear brake. Just as using the trailer brakes alone can stop a trailer from uncontrollably swaying side to side, using the rear brake on a motorcycle can add stability when entering a corner.

On a road racing machine, riders brake so hard that the rear wheel is often in the air, and the rear brake has minimal effect through the majority of the braking zone. As the rider releases the front brake and arcs into the corner, load does transfer to the rear and more rear brake can be used during this brief transition. That said, this typically can be managed using engine braking, either through electronic controls or an adjustable slipper clutch, and many riders do not use the rear brake at all on track.

The situation is much different for street riders, however. Data shows that even at a "spirited" pace for most riders, braking forces on the street are considerably less than those seen on the track. This means that there is typically much more load on the rear tire under braking, even in a straight line and especially entering a corner. This additional load can tolerate significantly more braking than the engine alone can provide, and now the rear brake is more effective. Using additional rear brake and less front brake will reduce the chance of the front tire locking up, and at the same time - using the trailer analogy - will add stability to the situation.

Take a step back from the sport bike realm, and the effect is even more noticeable. Standard bikes, sport touring bikes, and especially cruisers and touring bikes don't have the front-end bias of a sport bike, leaving plenty of load on the rear tire that can be put to good use for braking.

The takeaway here is that while riders on the track may use little or even no rear brake, on the street it is a much more effective tool for not only increasing safety, but also influencing the handling of the machine. Cornering ABS and stability control functions use this to look after the safety aspect should you get into trouble some day, but using the same concept, pro-active use of the rear brake has both safety and performance benefits.

Wednesday, 11 January 2017 14:53 Published in Andrew Trevitt


Street to Track Blog: Track Days, Part II

To be totally honest, my first track day of 2016 started out as a complete disappointment. I arrived at Castrol Raceway's road course confident and ready to ride, having just successfully completed Justin Knapik's On Track Performance Race School less than 24 hours earlier. In seemingly no time at all, my intermediate group received a five-minute warning, and in the time that it takes to start your bike, put on your helmet and gloves and line up, I was out on the track.

Monday, 14 November 2016 12:40 Published in From Street to Track with Patrick Lambie


Trevitt's Blog: Electromagnetic Valve Control (video)

While variable valve timing has been a hot topic over the last few weeks with the introduction of the updated GSX-R1000 featuring Suzuki's innovative mechanical VVT system, many companies are working toward the next step in this area: eliminating camshafts completely and controlling the valves directly using electromagnetic actuators. There are many stumbling blocks to electromagnetic valve actuation (EVA), but a research group in the Control and Automation Laboratory of the University of British Columbia has created a new type of actuator that may make EVA a very realistic option in the not-too-distant future.

Monday, 31 October 2016 13:47 Published in Andrew Trevitt


From Street to Track: Track Days, Part 1

There is nothing that can replace the one-of-a-kind adrenaline rush that accompanies pushing the limits of a modern motorcycle. Having accepted that the most appropriate setting in which to do so is in a controlled environment, I dedicated the 2016 season to the track. After investing time and resources into preparing the bike, accumulating gear and equipment, and completing a race school, the next step was all about getting seat time, and for me that means track days.

The premise of a track day is really simple. For a fee you get to take your bike out onto the track and put in as many laps as the allotted time or your personal stamina allows. This particular type of adventure starts when you register for the session. For those who have never participated in a track day, the cost may seem steep, as much as $250 for the day, depending on the track and organization putting on the event. However, the math is really quite simple. If you get pulled over doing 160 km/h on the street you will, after a mandatory court appearance, incur fines that could reach a thousand dollars or more, plus legal fees. Conversely, when you hit 160 km/h, 200 km/h or even faster on the track, you get an ear-to-ear smile.

The other thing that typically happens during the registration process is that you are asked about which group level you will be riding in, usually described as novice, intermediate or expert. Some organizations provide very specific criteria while others leave it to you to assess. Basic rule of thumb is to be honest. If you are new to the track and have never completed a high performance on track school, you need to be in the novice group. At the same time if you are an expert level racer with black number plates on your bike, lapping in anything other than the expert group will quickly become a frustrating experience.

Upon arriving at the track it is time to focus on unloading and setting up your bike, gear and equipment. For those of us who transport our bikes in the back of a pickup truck, unloading and loading can be a challenge. The good news is that motorcyclists being motorcyclists, there are always multiple people ready and offering to help. If it is your first track day or a new track, one piece of advice is to ask for a pit area close by the organizer's tent or booth, and let them know. Their business model is built around you becoming a repeat customer, so they will definitely want you nearby where they can make sure you are having a good time and finding everything you need.

Once you are setup and have signed in, the next item on the agenda is the rider's meeting. This is the time when the organizers will welcome you, tell you what to expect during the day, review current track conditions and cover procedures and safety protocols. It doesn't matter where you are or how much experience you have, these meetings are not only mandatory but they are important. Not every group or track has the same rules, and something as universal as a red flag can have different implications for riders on the track at the time of the incident.

With all of the formalities out of the way, take some time to walk around the pit area to say hi to old friends and make some new ones. Then head back to your pit, get into your riding gear and warm up your bike. Before you know it they will be calling your group and it will be your turn to head out in the track, which is where we will pick up next time.

Thursday, 27 October 2016 14:17 Published in From Street to Track with Patrick Lambie


Trevitt's Blog: What's a Qualifying Tire Worth?

At the final rounds of this year's Mopar Canadian Superbike Championship series, held at Canadian Tire Motorsport Park, Dunlop offered qualifying tires to the top 10 riders for a separate, 15-minute final qualifying session. This was new for many of the competitors, as qualifying tires have not been used in the series for several years. Jeff Williams was one of the riders in the top-10 session, and I was able to get some data from the Accelerated Technologies Honda CBR1000RR that he was riding for the weekend.

Tuesday, 06 September 2016 11:23 Published in Andrew Trevitt


Street to Track blog: School's in!

So you arrived the racetrack, unloaded your motorcycle, attended a riders meeting, jumped on the bike, and rode out onto to the track. And then, before you knew it, you were sitting in your pit reflecting on a day that feels like it flew by in an instant.

More than likely, somewhere near the front of all the thoughts and emotions working through your mind, is one question: “How do I go faster?”

One option is spend a bunch of time at the track and try to mimic the “fast” guys, but that's only good if they actually know what they are doing; otherwise, you are just learning a bunch of bad habits.

If you are serious about exploring your full potential on the racetrack, a more practical and proven approach is to check out schools in your area. For me this involved a visit to the On Track Performance Riding School in Edmonton. Owned and operated by multi-time EMRA and Western Canadian Superbike Champion Justin Knapik, the school offers multiple classes including two levels of performance riding. On Track Performance also runs a dedicated race school designed to assist you in attaining the licence required to complete at events held by the EMRA and other road racing organizations.

A goal of racing in 2016 led me to sign up for the race school, and I could not be more pleased that I did. During the classroom session Justin’s natural and effective teaching style delivered concisely laid-out information in a manner that conveyed his passion for racing, learning and safety. The following day the classroom gave way to on-track lessons where a ratio of only 2 students per instructor, all expert level racers themselves, provided the perfect learning environment. As the course drew to a close, not only did I feel prepared to race, but my overall riding skills had taken a quantum leap forward.

So what did I learn? Over a two-day period Justin and his team covered so much information that it would be impossible to summarize it in this blog entry. What I can say is that after learning about items like throttle control, braking, visual cues, proper body position, and how to develop effective lines, my number one takeaway was the fact that before you can be fast, you first need to learn how to be smooth. Anyone with decent riding skills and no fear of crashing can hammer their way around the track, but if you want to be truly fast, you first need to master the fundamentals. Accomplishing this involves making the investment into proper training and then practicing everything you’ve learnt until it becomes second nature. During this time you will need to accept that the focus on skills will take precedence over being fast, but as you progress, the speed will materialize and you will realize your goals. While it may take longer and cost more than just thrashing your way around the track, the end result will definitely be worth it.

I would be remiss if I did not take this opportunity to thank Justin Knapik for inviting me to participate in the 2016 On Track Performance Race Licensing School. It was an incredible experience, which I highly recommend.

Wednesday, 24 August 2016 13:26 Published in From Street to Track with Patrick Lambie


Street to Track Blog: Part 3: Pre-track prep

Your bike is all ready and it's time to head to the track. Not so fast. Preparing the bike is just one step of many, and inadvertently skipping even one item has the potential to ruin your time at the track before it even begins. With this in mind, here are a few items to consider.

Thursday, 21 July 2016 12:28 Published in From Street to Track with Patrick Lambie


Andrew Trevitt's Blog: Transfiormers - Daring to be different in a sea of Moto2 uniformity

Last month, Spanish rider Ricard Cardus won an FIM CEV (Campionato Espagnolo Velocita, a European Championship) Moto2 race at Catalunya in Spain. That in itself is not overly surprising; Cardus has been racing in the Moto2 World Championship for several years with a handful of top-10 finishes to his credit. What's more noteworthy is the motorcycle he was aboard: Transfiormers.

Friday, 08 July 2016 16:31 Published in Andrew Trevitt


BLOG: From the Street to the Track with Patrick Lambie: 2nd installment - Bike Prep

After making the decision to head to the track this season, my attention quickly turned to determining what bike I should take with me. While momentary consideration was given to acquiring a bike specifically for track days and club racing, there was never really any doubt that it would be anything other than my trusted 2006 Honda CBR600RR taking this new adventure with me.

Friday, 10 June 2016 17:04 Published in From Street to Track with Patrick Lambie


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