Honda Scooter Engine 150cc
Honda (Worldwide) announced an new mid-sized ‘global standard engine’ for their future 125cc scooters. This new motor is a 125cc liquid cooled 4-stroke that will be used in quite a few future scooters starting next year. Honda hasn’t announced any specific scooters that will use this engine yet, but it’s good to get to know this motor, as it will likely make it to the North American market in some form in the future years.

Honda announced this motor as a ‘global standard engine’, which means they will eventually create quite a few variations to meet different price points and scooter designs (ie. different swing arm lengths to accommodate different wheel sizes). On first glance, this motor might not look like anything radical, but there are a number of nice improvements that will benefit scooterists. Honda claims they focused on three areas with this new motor: durability, fuel economy and quietness. The most interesting of these areas is the fuel economy.

This engine ‘accommodates an idle stop system’, which means that higher end scooters sold in places like Europe and Japan will get the idle stop system which shuts off the engine at stop and instantly restarts it, while in other markets Honda will cut costs and omit this system. Honda’s first scooter to incorporate an idle stop system is the 2011 PCX 125, which doesn’t get this system in the USA market, but does elsewhere. Like the idle stop feature, fuel injection is another feature that this engine ‘accommodates’, so most markets will get that but some countries will get budget versions with carbs.

Honda claims a big overall improvement in fuel economy of 25%, which likely assumes the use of both the idle stop feature and fuel injection. Honda also improved fuel economy by making a big effort to reduce friction in many areas of the engine. This friction reduction has been accomplished by a large number of small tweaks. Some of the more note worthy ideas are needle bearings on the rocker arm shafts (most scooter engines have no bearings here and just rely on oil), roller rocker arms (very cool, a 125cc scooter first), an offset cylinder to reduce friction against the wall (see diagram below), a more efficient radiator which requires a smaller lighter fan, lighter piston, less oil agitation in the transmission etc. Ideas like idle stop technology and fuel injection are already present on some Honda 125cc scooters, but the needle bearings on the rocker arm shafts and the roller bearing rocker arms (on left where they contact the camshaft) are an industry first in a 125cc scooter and very nice to see. These features are normally only seen on higher end motors.

Honda PCX 150 - Motor Cut away
Fuel economy and friction aside, Honda has made a few other neat tweaks. They’ve found a new ‘high-elasticity’ rubber for the drive belt that is both quieter and more efficient which is good news. Typically scooter CVT’s are only about 80-85% efficient, so there is some real room for improvement here. Honda has also included a brushless ‘ACG’ starter which has been seen on a few other Honda’s before this (ie. Honda Ruckus, Metropolitan and PCX 125). This ACG design is great (simple, lighter and silent) and for this new generation of engine Honda has increased their electronic control over this starter to make the idle stop system work better and all starting easier.

One thing that stood out from Honda’s press release, was this motors similarities with the current Honda PCX 125 engine (idle stop system, fuel injection, 125cc displacement, ACG starter etc). Digging a little deeper revealed that the bore (52.4mm) and stroke (57.9mm) of this new engine are coincidentally identical to the PCX 125 motor. Accordingly, this ‘new’ engine might be better considered as a new generation / refinement of the current PCX powerplant. While likely PCX based, the engine improves in a large number of areas including overall weight, lower friction in the transmission, offset cylinder, new drive belt material and the great roller rocker arms and needle bearings on the rocker arm shafts.

Honda's new Offset cylinder
Honda plans to announce the first models using this engine next year as 2013 models. The USA/Canada might get this motor in an updated 2013 PCX 125, or North America might lag a bit further behind and not receive this motor until the 2014 model year. There’s also the possibility Honda won’t roll it out here for a number of years until they replace the PCX 125 with a new model. Honda is impossible to predict for the North American market, but I do think they’ll make an effort to get this engine here eventually.
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