LC10 was the original name given to a series of very small three-cylinder, two-stroke engines built by Suzuki Motor Corporation in the 1960s and 1970s. They were used in a number of kei class

Kei car

Kei cars, K-cars, or , are a Japanese category of small vehicles, including passenger cars, vans, and pickup trucks. They are designed to comply with Japanese government tax and insurance regulations, and in most rural areas are exempted from the requirement to certify that adequate parking is...

 automobiles and light trucks. The LC10 and its derivatives did not completely replace the FE and L50 two-cylinders, which continued to be used mainly for light commercials. The LC10 engine was developed together with the Suzuki B100 engine, a 8 PS 118.9 cc single-cylinder motorcycle engine which shared the same bore and stroke. For longevity and convenience, the LC10 received Suzuki's new "Posi-Force" auto-lubrication system, eliminating the need for pre-mix.

LC10

The engine was first seen in air-cooled form, equipped with three Mikuni VM carburettors, in the 1967 LC10 Suzuki Fronte 360. Displacement was 356 cc, from a bore and stroke of 52.0 and 56.0 mm. Originally developing 25 PS, a 36 PS SS version soon appeared, with a stunning 101.1 PS/L. For the conventionally laid out Fronte Van, Estate, and Custom a single carburettor version was used.
In 1969, Japanese racing car manufacturer Nialco built a single-seater called the RQ which utilized the triple-carb LC10 engine and competed in the RQ ("Racing Quarterly") Minicar Racing Tournament. Their best result was a fourth in the 1969 meet at Fuji, with Kikuo Kaira (future co-founder of Tommy Kaira

Tommy Kaira

, formally , is a Japanese car tuning and manufacturing company founded on May 1, 2002 and headquartered in Minami-ku, Kyoto, Japan. The company was named after its two founders, Yoshikazu Tomita and Kikuo Kaira. Its parent company was originally founded in 1968 as...

) at the wheel.

Applications:

• 1967.04–1970.11 Suzuki Fronte 360
• 1970.11–1973.07 Suzuki Fronte LC10 II ("Sting Ray" Fronte)
• 1969.01–1972.03 Suzuki Fronte Van/Estate/Custom LS10/11

LC10W/LC20

In May 1971, as kei cars were becoming more and more sophisticated, a water-cooled version was presented. The air-cooled versions were soon relegated to use only in the cheapest versions, and disappeared entirely after 1973 as emissions standards became more stringent. The watercooled versions also had slightly better weight distribution (38/62 versus 37.5/62.5), due to the radiator being mounted up front. This, the LC10W, was the only engine ever to be installed in the iconic Suzuki Fronte Coupé, whether in domestic or export market cars. When installed in the 1973-1976 "oval shell" Fronte, this engine was called the LC20.
From 1973 the LC10W/LC20 engines also received Suzuki's SRIS (Suzuki Recycle Injection System), a method for lowering visible exhaust smoke by collecting and burning residual oil/gas laying in the bottom of the crank chambers. This was first seen on the Suzuki GT750, GT550

Suzuki GT550

The Suzuki GT550 is a two-stroke, air-cooled, three cylinder 1970s-era motorcycle in Suzuki's "Grand Touring" GT series. Even though total production of the 550 exceeded 60,000 examples spread over a six model year production run, this total was exceeded by both of its three cylinder GT series...

, and GT380 motorcycles. In an effort to reduce CO

Carbon monoxide

Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

, HC

Hydrocarbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....

, and NO_x

NOx

NOx is a generic term for the mono-nitrogen oxides NO and NO2 . They are produced from the reaction of nitrogen and oxygen gases in the air during combustion, especially at high temperatures...

 emissions, the EPIC (Exhaust Port Ignition Cleaner) system was also installed.

Applications:

• 1971.05–1973.07 Suzuki Fronte LC10 W
• 1971.09–1976 Suzuki Fronte Coupé
• 1973–1976.05 Suzuki Fronte LC20

LC50

A bored-out version (60.0 x 56.0 mm) of the air-cooled LC10, called the LC50 in reference to its near half-litre displacement (actually 475 cc) appeared in January 1969. In street applications, this engine was only for export, and was only ever made with air cooling. Like its smaller brethren, the LC50 breathed through triple carburettors.

Water-cooled 475 cc triples were built for racing purposes, producing 60 PS at 9,000 rpm. These took part in the JAF Grand Prix Formula Junior

Formula Junior

Formula Junior is an open wheel formula racing class first adopted in October 1958 by the CSI . The class was intended to provide an entry level class where you could use inexpensive mechanical components from ordinary automobiles...

 class as well as "MR" (Minicar Racing) meets. Thus equipped, the Can-Am style Fronte RF with Itou Mitsuo at the helm took the victory at the 1970 "Junior Seven Challenge Cup" race, held at Fuji International Speedway, with an average speed of 130.9 km/h.

• 1969.01–1970 Suzuki Fronte 500
• 1970–1973.07 Suzuki Fronte 500/LC50 ("Sting Ray")

T4A

In response to the changed Kei car regulations taking effect on January 1st 1976, Suzuki developed a bored out and cleaner version of the LC10W, featuring Suzuki TC (Twin Catalyst, a double muffler in which uncombusted fuel was burned) emissions equipment. The watercooled 443 cc engine's bore was 58.0 mm, while retaining the 56.0 mm stroke. Sometime between 1973 and 1976 Suzuki had changed their system of naming engines, so this engine became the T4A. This meant that it was the first ("A") engine with a 0.4-litre displacement. The T4A was fairly short-lived (only used in the Fronte 7-S for a little over two years), and was soon replaced by an unrelated "full size" (550 cc) engine called the T5A/T5B. The emissions strangled T4A put out a lowly 25 PS at 4,500 rpm in its final "TC53" form: specific power was a mere 54% of what a 1972 Fronte GT had managed.

• 1976.05–1978.09 Suzuki Fronte 7-S SS10/SS12