THE HONDA CR-125 ENGINE BY SWEDETECH

TKART Staff

17 January 2017

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 Honda Shifter belongs to the gearbox “family” of karting engines. It has a 6 gear manual transmission

HOMOLOGATION
Honda CR-125 1999-2002 unlimited engine

A prestigious name (Honda), that is motorcycle-derived, and "preparation" for karting (by SwedeTech). This is what the Honda CR 125 engine looks like for racing in the SKUSA (SuperKartsUSA) Honda Shifter S4M class.

If you say "Honda", European enthusiasts automatically think motorcycles, or at most, McLaren F1 engines. To an American, however, Honda, besides all this, also means karts, since the brand is one of the most widespread even among kart drivers, with different categories dedicated exclusively to motorcycle-derived engines of the Japanese company. The Honda CR-125 engine has, for many years, been an example. In fact, taking advantage of the SKUSA stability regulation, the characteristics of engines have remained almost unchanged since the first years of production (1999-2002). In addition, being derived from a motorcycle, albeit with some technical changes, allows maintenance intervals that are less frequent than a conventional KZ engine, albeit with markedly different performance. To better understand the characteristics of the engine and differences compared to the KZ, TKart went to Las Vegas to talk to Jason Barry, manager of the important specialised team in the preparation of 2T engines, SwedeTech.

Jason Berry, manager of SwedeTech, posing next to the Honda CR 125 engine prepared by his team to race in the 20th Anniversary SuperNationals in 2016.

The differences between the Honda (above) and KZ (below, the TM KZ 10C) engine are, in particular, the fact that the former was developed for motocross, while the latter was designed specifically for karts

The main difference between the 2 engines is the reversal of the positions of the carburetor, intake and exhaust. The Honda engine has the rear intake in line with the direction of travel and the front exhaust. The KZ is the opposite.

Among them, the exhaust for a specific karting application, clearly different from the original motocross exhaust, is approved by SKUSA. Even the plate that allows the attachment of the engine to the chassis must be purpose-made: SwedeTech builds them "in house".
As for the silencer, with the Honda it is free, but if the noise is excessive the judges can get it replaced.
The air filter is also free, with a circular shape and retina system, while for the KZ has a plastic "air box" approved according to strict noise and particulate emission limits.

There are 5 transfer ports on both cylinders. The Honda exhaust instead has two main lights separated by the central bridge, while the KZ has a rounded central light with two boosts at the sides.
The carburetor is always the guillotine type: the Japanese Keihin for Honda; the Italian Dell'Orto for the KZ.
In addition to the greater power, the best performance of the KZ compared to the Honda also stems from being "native" to a kart. In fact, this allows the design of the engine so that it is perfectly suitable for to the chassis, ensuring significantly higher final performance. In contrast, the Japanese engine has more torque at low revs.

Because the project has a motorcycle origin, the Honda engine is modified with a system that reproduces the supply of fuel from above, like a tank

The SKUSA approved exhaust (above) and the base (belowe), specially made by Swedetech, to adapt the Honda engine to a kart chassis