KTM LC4 engine

KTM LC4 Engine is series of single cylinder engine designs produced by KTM debuting in 1987. "LC" in the name stands for Liquid Cooled while 4 indicated a 4-stroke motor. Starting development in 1982 it was designed to replace air-cooled 4-strokes with an eye toward future emission standards. The first engine introduced was the enduro racing 553 cm³ 600GS. The basic LC4 design has gone on to power a range of KTM Motorcycles.

History

The LC4 engine has increased in displacement over the years. The original 600 (553 cm³ actual) gave way to the 620 platform (609 cm³ actual) which became the 640 series (625 cm³ actual) from 1999 onward, then on to the 2008 version of the 690 (654 cm³ actual) the 690 v2 (690 cm³ actual) to its current 690 v3 (693 cm³ actual) size.

Used in various KTM models the LC4 equipped bikes have had various engine size related designations:

• 1987 - 600GS
• 1994 - 620 Duke
• 1997 - 620 EGS/Adventure
• 1998 - 640 Supermoto
• 1998 - 640 Adventure-R
• 2008 - 690 Enduro R
• Other Variants include multiple Badge engineered models

See also: KTM 690 series

2019

KTM introduces twin balancer shafts with the 690 LC4.

2026

KTM releases the significantly redesigned 690 LC4 increasing the displacement to 692.7 cc (42.27 cu in) with an increases to 77.9 hp (58.1 kW) @8000 rpm and slightly reduced 53.9 ft⋅lb (73.1 N⋅m) of torque @6750 rpm. KTM made these changes, reclaiming the “world’s most powerful” single-cylinder title, in response to the announced specifications for the Ducati Superquadro Mono.

LC4c

See also: KTM 390 series

In the 2023/24 timeframe KTM designated their new 398.6 cm³ motor LC4c.

External links

• "The most powerful single-cylinder in the world", Ducati.com, retrieved 19 May 2026
• Nye Davis (10 Sep 2025), Here's how KTM built the world's most powerful single-cylinder engine for a road-legal motorcycle