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Small package packs a big punch

by JohnNicholas on 09/23/2009

YMA is pleased to announce a new locally developed variant to its comprehensive motocross lineup… the powerful and compact YZ144 two-stroke racer.

The YZ144 has been developed in Australia primarily to compete in up to 150cc two-stroke classes where it will line up alongside juniors on similar capacity machines and 250cc four-strokes in the senior Lites class.

The new machine is based around YZ125 but features increased power across the rev range and has been thoroughly tested to ensure the high level of reliability customers expect from Yamaha products.

YZ144 action

The combination of a powerful yet reliable 144cc engine mated to six speed gearbox fitted into a lightweight YZ125 chassis is sure to be a serious contender not only in the Junior up to 150cc two-stoke class but also MX/SX Lites and Class 1 off road competition where two-strokes up to 200cc compete. And it is guaranteed to offer a high level of excitement to thrill seeking dirt bike riders whose main goal is fun.

The YZ144 has been developed in-house by Yamaha Racing Development (YRD) following intensive research and testing. It features modifications to crankcase, cylinder and head as well as custom made piston and ring to produce a bore and stroke of 58mm x 54.5mm (= 143.9cc).

In order to aid and promote maintenance, each YZ144 is fitted with an hour meter, Servicing intervals are as per YZ125 recommended intervals. This is not a backyard bolt-on kit and due to the amount of machining work involved, there is no plan to offer the parts as a kit. The following modifications have been made to the standard YZ125:

Modified crankcase set
Modified cylinder and cylinder head
Modified L+R power valves
58mm custom made piston (made in Germany)
Custom made piston ring (made in Germany)
Hour meter
Graphics set (front guard, rear guard, L+R radiator shroud)
Carburettor jets

All other specifications are as per YZ125, it even sports the standard YZ125 exhaust system. Dyno tests in this ‘as sold’ standard trim reveal a healthy increase in power across the entire rev range (see graph above). Owners wishing to increase power further will have several other options available.

For example, Cisco’s Race Tuning has several power up levels available that include:

Custom ported cylinder
Specific 144cc exhaust system developed by HGS
Crankshaft modifications (1mm off set crank pin) that will provide a further capacity increase to 149.2cc (class limit is 150cc).
VHM 144 cylinder head
V Force reed valve assemblies
HPI programmable ignition units

YZ144 is now available in limited numbers via the Yamaha dealer network priced $9599 RRP inc GST.

Type                               Liquid-cooled, 2-stroke, reed valve
Displacement – (cc)    143.9
Bore Stroke – (mm)    58.0 x 54.5
Compression               8.6 ~ 10.7:1
Lubrication                 Premix
Fuel Management     Mikuni TMX 38
Ignition                        CDI
Starter                          Kick
Fueltank – (L)             8
Oil Capacity – (L)       0.7
Transmission             6-speed
Length – (mm)           2135
Width – (mm)            827
Height – (mm)           1315
Seat Height – (mm)  997
Wheelbase – (mm)   1443
Clearance – (mm)     386
Wet Weight                95kg with 8 litres of fuel
Suspension Front     Telescopic fork
Tyres Front                80/100-21 51M
Brakes Front             Single disc
Suspension Rear      Swingarm
Tyres Rear                 100/90-19 57M
Brakes Rear               Single disc
RRP (inc GST)          $9599

For more technical information, contact John Redding at YRD: (03) 9761 5871 or email:

For further tuning info, contact Cisco’s Race Tuning at (03 9725 1330), email:
Press release             All new YZ144 released      18 Sep 2009

YZ144 is fitted with race graphics kit

In standard trim the YZ144 shows a healthy power increase across the whole rev range over YZ125

Lites class weapon YZ144 is based on the awesome YZ125 but features more horsepower across the range

Float like a butterfly, sting like a bee: the YZ144 is set to prove that two-strokes can be reliable, competitive and a viable alternative to a 250F