A man’s dream: a supercharger. We installed it on a 250cc single-cylinder Z250SL and rode it.

Performance that cannot be achieved with naturally aspirated engines

In this article, which will be divided into two parts, we will introduce a Z250SL equipped with a supercharger and a CBR250R equipped with a turbocharger, both built by Bike Shop Andy. However, turbos and superchargers are hardly common mechanisms in the world of motorcycles, so before we get into the main topic, we will provide an overview of superchargers.

To send large amounts of air into an engine. Put simply, that is the role of a turbocharger. While the purpose and application vary over time, such as power-up, downsizing, fuel economy, and air-fuel ratio correction, the common mission of all turbochargers is to rotate the parts inside the unit to send air compressed to above atmospheric pressure into the engine, achieving performance that cannot be achieved with naturally aspirated engines.

Broadly speaking, there are two types of turbochargers: turbos, which use energy from exhaust gases to spin a turbine, and superchargers, which use power from the engine to run the turbocharger (however, both are now available in electric versions. In other countries, turbos are also considered a type of supercharger), so it’s difficult to say which is superior. In fact, the two types of turbochargers coexist in the four-wheeled world, and some vehicles even use both turbos and superchargers.

Emphasis on fun on mountain roads and ease of handling in everyday use

Now, finally, to the main topic. When it comes to superchargers in the world of motorcycles, most people will focus on maximum power output and top speed. However, Ando-san of Bike Shop Andy says he isn’t particularly interested in absolute speed.

“In the past, I’ve recorded a speed of 137 km/h on a supercharged Address V125, but the supercharged cars I build generally prioritize fun on mountain roads and ease of handling in everyday use. It would be a shame to add interesting parts only to be able to enjoy their performance on long straights.”

Ando-san previously focused on 125cc scooters, but has now shifted his focus to 250cc single-cylinder road sports. In addition to the two bikes introduced in this article, he also produces supercharged versions of the Rebel 250, CB250R, and YZF-R15.

“The origin of my turbochargers goes back to the CB250RS turbo I built for myself about 20 years ago. So rather than changing the main focus, I think it was right to go back to my roots. I think the appeal of a 250cc single-cylinder road sports bike is that it gives you a feeling of agility that’s different from a 2/4-cylinder bike with the same displacement or one over 400cc, and that maintenance costs are low. However, there are many times when I feel the engine is lacking in power on mountain roads, so I installed a turbocharger to compensate for that.”

When I heard that, I thought it made sense, but I actually had some doubts about the necessity of a turbocharger. That’s because in the case of the Z250SL and CBR250R, you can increase the displacement by using parts for the export-spec KLX300 and CBR300R, and even before that, if you choose a 400cc single-cylinder bike from KTM or Triumph, you can solve the lack of power in the engine (of course, maintenance costs increase if the displacement exceeds 251cc). Also, I couldn’t help but wonder whether a turbocharger would be able to run properly on a 250cc class bike.

For this reason, I went into this test drive with mixed feelings… But after thoroughly experiencing the two supercharged vehicles in city streets and on winding roads, I was completely enlightened. In the following article, I will introduce the ride quality of the Z250SL + supercharged vehicle.

Z400SL…isn’t it?

I was surprised at how powerful and torquey it was. 　I had seen the actual measurement data before the test ride, and knew that maximum output had increased from 29 to 42.5ps and maximum torque from 2.4 to 3.1kg-m, but the Z250SL + supercharged model was supercharged in every range, from the low rpm range just above idle to the high rpm range, and I could feel the powerful acceleration that exceeded the standard in every range. The difference with the standard model that Ando-san had prepared for comparison was clear, and at first I had the impression that it was a Z400SL?

However, that description is not accurate. The faithful response to the rider’s inputs and the sharp acceleration felt across the entire range are unique to a 250cc engine, where the moving parts inside the engine, such as the pistons and crankshaft, are light. If the engine displacement were increased by using the φ78mm pistons used in the KLX300 (φ72mm for the Z250SL), you would not be able to experience this light and nimble feeling.

And speaking of lightness, this test ride made me realize once again the light handling that is unique to the 250cc class. This may contradict what I said earlier, but I don’t think you can get this same sense of nimbleness and freedom with the 400cc single-cylinder bikes sold by KTM and Triumph, which weigh just 170kg (the Z250SL is 148kg).

In any case, I was very impressed with the ride quality of the Z250SL + supercharger. What’s even more surprising is that the two bikes built by Bike Shop Andy had absolutely no negative aspects compared to the stock bikes. There was not even a trace of the harshness that many people associate with the word “supercharger.” I was able to open the throttle boldly when exiting corners on mountain roads, and I was able to ride easily through congested roads in the scorching sun with temperatures around 35 degrees Celsius with the same feeling as the stock bike.

Detail explanation

This 250cc single-cylinder engine explodes with turbo power at high RPMs 　, giving it a two-stroke feel. Andy’s supercharged bike | Motor-Fan is a media platform focused on automotive-related articles.

The Difference Between Turbo and Supercharger This article introduces two 250cc single-cylinder + supercharged motorcycles built by Bike Shop Andy: a CBR250R + turbocharger and a Z250SL + supercharger. By the way, the turbo […]

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