[4] In Suzuki's numbering scheme, automobile race tracks identify each of its 3-cylinder GT bikes for the North America market: Sebring for the 380, Indy for the 550 and Le Mans for the 750.

[1] Suzuki Recycle Injection System (SRIS) was an attempt by the manufacturer to reduce visible emissions from a two stroke motorcycle.

The SRIS consisted of a small check valve in the bottom of each crank chamber along with various lengths of elastomeric tubing to the transfer ports of adjacent cylinders.

Two stroke engines have a tendency to collect unburnt oil and fuel in the bottom of the crank chamber at idle.

Upon acceleration, after a period of idling, the unburned oil and fuel gets sucked up the transfer ports and contributes to an overrich mixture for the first 5 to 10 seconds resulting in a smokescreen from the exhaust.

Overall fuel and oil consumption was unchanged but visible smoke was greatly reduced on sudden acceleration from rest.

Suzuki began using automatic lubrication in 1966 to eliminate premixing of oil and fuel as had been the norm for all two strokes up until then.

This system was launched to eliminate mixtures with far too much oil due to the operator's unnecessary effort to preclude engine seizures.

This type of undersquare engine configuration has long since been discarded for use in street bikes by most Japanese motorcycle engine designers due to its inherent limitations on power increases and the recent advances in combustion chamber design allowing the use of large bore cylinders and high compression without detonation issues.

Both the wheel and the other fork leg were capable of accepting another disc and caliper and a switch to a twin-disc front brake (like the GT750) was not an uncommon modification some owners made (although the larger master cylinder from the 750 was required).

The instrument cluster still contained the speedometer and tachometer but a single digit LED gear indicator was added.

[7] In 1975, various external and internal parts of the fork were changed, the engine was re-tuned to 53 hp now with chrome bores plated directly onto the alloy barrels and the bike was heavily restyled.

The North American area kept the exhaust coupler tubes and older engine tune of 50HP with cast iron cylinder liners through to the end of production.

[7] The faces of the speedometer and tachometer were changed from a blue background to brown to match the appearance of the instruments on the GS models.

Rear light changed to GS style, Satin black side panels and GS style indicators A January 1973 Cycle World road test said the GT-550K Indy was a good compromise between the GT750 Watercooled and the GT380, with substantial enough weight and size for to long-distance touring with a passenger, and being only just light enough and narrow enough, with a 150 mm (5.8 in) ground clearance for "deft canyon road maneuvering or hustling through traffic".