The PZ490 is a 490cc single cylinder 2-stroke motorcycle which was tuned and optimised for the Roof of Africa Extreme Enduro in Lesotho in November 2023. Riempies successfully completed the roof, despite very hot conditions
Our design engineer Riempies Pretorius will compete on it.
Frame
This engine is housed in a 2012 KTM 300XC enduro bike frame which we just so happened to own.
Engine
The engine uses the clutch and gearbox from the donor KTM 300XC bike to reduce weight and space, but they are housed in a completely new billet machined set of engine casings, designed to accommodate the big crank shaft and cavernous barrel. The engine will produce a whopping 77% more horsepower @ 6000 RPM than the donor engine so we expect some gnashing of gear teeth and arm-stretching along the way!
The rest of the engine was designed and produced by Team Matjien and our willing partners and sponsors, and includes billet machined crank, balancer shaft and gears, engine casings and covers, 2-piece cylinder head as well as rapid prototype investment casting of the cavernous Nikasil lined barrel. You name it, we designed it and had it manufactured.
The development process used as many modern technologies as practical given our limited budget, from computer simulation of engine performance using Vannik engine development software, through to tractive effort simulation. We used the tractive effort simulation to compare engine performance and primary drive gearing with that of the 300XC, and used the data to smooth out power delivery and calculate the first order sprocket size.
We 3D scanned and CNC measured all of critical dimensions of the original 300XCW engine casings as inputs to the CAD design. Then we 3D printed of all newly designed components in plastic for a preliminary fit of new and donor components. We also made a first order 3D printed plastic engine to check the fit into the donor 300XC frame.
We used this 3D printed plastic engine mounted in the frame to generate the first order layout of the substantial new expansion box (exhaust). This initial layout was transferred to a CAD design. Here the details of all the little pieces of exhaust that make up the snake leading from the barrel to the rear of the bike were developed. Using CAD to eased the load on the exhaust fabricator. This job gave Riempies sleepless nights, but we came up a novel plan to speed up this process! As you can imagine, keeping the substantial exhaust of this beast out of harm’s way in the Lesotho rocks is a serious challenge which is an issue we are attending to in a novel way.
The barrel and head for the fitment process was also 3D printed in plastic as part of the preliminary fitment in the bike and then the real aluminium barrel was cast using rapid prototyping investment casting. It was machined and then sent for Nikasil treatment of the inner sleeve.
Engine specifications:
This engine is near state of the art with the following features:
• Electric start with Li-Ion battery for reduced weight and improved performance.
• Automatic decompression valve to ease starting.
• Electronically controlled power valve to smooth out mid-range power delivery.
• Boyesen fiber reed valve block with 38mm flat slide Mikuni carburetor.
• Digitally tunable electronic ignition.
• Balancer shaft system for reduced rider fatigue and improved power delivery. The balancer shaft and primary drive gears were designed and produced by PVZ Gears.
• Custom designed and hand-built expansion box and silencer using VANNIK 2-stroke development software.
• Rapid prototype investment casting of Nikasil lined barrel.
• Billet machined 2-piece cylinder head with an insert for the combustion chamber which makes it easier and cheaper to change compression ratio if required.
• Billet machined crank shaft and balancer shaft by P&C Technologies.
• Billet machined engine casings by Elinem Engineering.
• Forged Wiseco CR500 piston, conrod, crank pin and big end bearing.
• Max power is 48kW (65hp) @ 7000rpm and max torque is 68Nm @ 6000rpm.
Posts
Follow the progress on our blog postings for the PZ490.