Under Review | IAME OK and OKJ, a lot of changes

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Under Reviews

IAME OK AND OKJ, A LOT OF CHANGES

Carlo Forni

20 June 2016

TYPE
Like most kart engines on the market, the RKZ is a 2-S. 4-stroke engines are still a small niche

125 CC

DISPLACEMENT
125 cc has been the standard for some time now, while in the past it used to be 100 cc

PUSH

START
Push-mode as in all KZ engines, with hand-release clutch and neutral to 2nd gear shifting

GEARBOX

TRANSMISSION
The following are the “families” of kart engines: gears and single speed. OK and OKJ are single speed clutchless engines

HOMOLOGATION
Certified under KZ homologation, just renewed and valid for the next 9 years, beginning in 2016

IAME is the engine company with the longest and most prestigious history in the international karting scene. It is 100% specialized in engines, and it has made many innovations for the new OK and OK-Junior class engines.

The most famous karting engine company in the world has managed the transition to OK engines using all its know-how, changing practically every single component. Following the flow of air and the mixture, from the reed valve pack inlet to the exhaust outlet, we can see all the Iame changes.
Let’s start with the OK class.
The first change can be seen in the reed valve pack: the spacer is made of resin rather than aluminium. This creates a thermal shield with the crankcase, with the objective of maintaining the reed valve pack cold: the incoming mixture does not heat and remains more compressed, benefitting the filling coefficient and, therefore, performance.
The spacer has also been made thicker and its shape has been changed. Following this, the inlet ramp from the reed valve pack to the crankcase has changed: to prevent the flow, which then goes towards the side of the transfer ducts, being “disturbed” by the air eddies generated by the rotation of the motor, IAME has realised a partially closed crankcase pump, leaving only the necessary movement of the connecting rod.
The transfer ducts have been modified in terms of volume and curvature, while the sections have remained similar.

Generally, without a starter motor, clutch or water pump (which is now on the outside), OK (see the picture above) and OK-Junior (see the picture below) are more compact than the “old” KF and KFJ. This has also resulted in a weight gain of about 5 kg

The crankcase pump has been modified compared to the pump of the KF and KFJ engines. Now it’s slightly more closed than before; in the OK class (see the picture above) is much more closed in the OKJ engine (see the picture below)

The reed valve pack spacer is made of resin, a material that enables a thermal insulation effect. In the OKJ there is an additional spacer between the carburetor and the conveyor

There are two new pistons in the combustion chamber, whose main feature is the virtually flat head. This solution, taken from the racing department, improves the flow from the transfer ducts into the combustion chamber and towards the exhaust. In turn, the pistons differ in relation to the height at which the rod is positioned. The side walls of the pistons are coated with disulphide using one of two systems: spraying or serigraphy.