Hezemans Rotax 100cc Reed Water Cooled

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Hezemans Rotax 100cc Reed Water Cooled ICA Engine

In the early 1990's, liquid cooling was still prohibited in most 100cc classes. Consequently, Rotax did not offer any liquid cooled 100cc kart engines yet. Around 1995, when some places started experimentation with allowing liquid cooling, Hezemans decided to introduce a 100cc water cooled ICA engine, based on an existing air cooled Rotax engine.
The crankcase of this engine most likely belongs to a Rotax VM95/Rotax VMD reed valve 100cc air cooled ICA engine. The cylinder barrel and head were designed and manufactured by Hezemans (allegedly in a factory in Portugal, but this needs more information). They were made to fit the Rotax crankcase and are interchangeable with the original Rotax parts.
Apart from the "Hezemans" branded version, there are also engines with the "ROTAX" name on the side of the cylinder barrel, see image gallery below. As far as known these engines are identical except for the logo.
These engines are distinct from the last attempt that Rotax made at a 100cc liquid cooled engine in 1999, the Rotax VMF family of engines.

Ignition: PVL analog system with 1092 bidirectional stator, 962 right hand turning rotor (since the ignition is on the unusual right hand side of the engine) and a standard 105 458 coil.
Engine Sprocket: like the Rotax VMD and Rotax VME models, these engines use a right hand side ignition and a closed crankcase half on the left. This construction uses an engine sprocket that is locked against the ignition rotor. These sprockets are difficult to source, but can possibly be machined from standard sprockets.
Ignition timing: TBD.
Spark plug: Heat range similar to NGK 9 for cold weather and NGK 10 for normal to hot weather.
Main crankshaft bearings: 6205 C3 or C4.
Oil seals: FPJ (teflon) double lip, 35mm O/D, 20mm I/D, 7mm thick.
Piston pin: TBD mm O/D, TBD mm long.
Piston pin needle bearing: TBD mm I/D, TBD mm O/D, TBD mm wide.
Big end pin: TBD O/D, TBD mm long.
Big end needle bearing: TBD mm I/D, TBD mm O/D, TBD mm wide.
Big end thrust washers: TBD mm I/D, TBD mm O/D, TBD mm thick.

The Hezemans version

The Rotax branded version

The Rotax branded version on a rotary valve (DSD or DSE) crankcase