A Field Guide to the Suzuki GT550
Model Year 1975 (M)
Please refer to the Country Specific Versions section for additional information about machines sold into your market.
1975 marks a major change point as the North American model engines (Canada and the USA) continued on with minor changes only, whereas models sold into the EU and elsewhere differed significantly. Regrettably, Suzuki did not use a different engine numbering sequence and so the two engine types have commingled numbers.
- Outside of North America, Nicasil coated cylinder ( SCEM in Suzuki terminology, and having a letter 'E' cast on the cylinder) and pistons using iron rings from engine no. 55829 (see German service bulletin #15 at this link)
- Extended cylinder base bolts on the carburettor side and a change in the upper crankcase casting to accommodate the new cylinders increasing the transfer port opening in the EU.
- 2 more ports were added to the EU cylinders giving better breathing - shown on the left in the photo below. The additional height of the new inlet tract is obvious in the photo on the right, and the 'E' on the casting is also visible.
- Ignition, starter motor, alternator and regulator by 'Nippon Denso'.
- Ignition timing 22 degrees BTDC in the EU. North American timing was unchanged.
- Changed final drive ratio from 16/40 to 15/36 in the EU - North American version unchanged.
- Early 'M' models used carburettor stamped with 34620 with all three main jets being #100. Later model 'M' machines were fitted with three #102.5 main jets and the carburettors stamped 34621. A further change was made with very late 'M' and early 'A' machines with carburettor stamping 34622, to having a #105 main jet in the left side only.
Below are pages from the 1975 Service Data manual manual showing the NA/EU differences at the start of the 'M' model year.I have more of the manual covering other models available at this link. Beside it is are the parts manual pages showing the carburettor changes late in the 'M' model production. Note also the needle jet and pilot jet changes.
Note: North American carburettors remained unchanged from the 'L' model 34111 type till the end of production.
- Modified compression ratio outside of North America.
- Power increase to 48.5 DIN hp (previously 48.0 DIN hp) outside of North America
- Max torque at 7,500 RPM in the EU instead of 6,500 RPM in North America, and a maximum RPM of 8,000 instead of 7,000 RPM
- Modified exhaust system with the removal of the cross coupler/ETCS system outside of North America
- From engine no. 63692, for all markets, the starter clutch was changed to from a 3-roller type to a 'Borg-Warner' type of clutch (it has been suggested that the new starter clutch unit had a 20,000 km warranty, however this has not been confirmed). The change is detailed in USA Suzuki Service Bulletin #26 which may be viewed at this link. In the photo below, the new style is on the left and the original style on the right.
- GT750 style forks (the chromed caps used in 1974 'L' model are now black rubber dust caps)
- Lower left fork leg had provision for a second disc brake.
- Mirrors with 10mm thread instead of 8mm with no vibration damper as fitted to the GT750.
- Shock absorbers now have shorter upper shrouds.
- Highly polished lettering with serif fonts on the tank, and the same serif font was on the back of the seat
- From frame no. 60904 : The entire rear brake assembly was revised. These changes are detailed in Suzuki Service Bulletin #33 which may be viewed at this link.
- Starting at frame number 60143 onwards, the spark plug covers were revised in the Ram Air shroud. This is detailed in Suzuki Canada bulletin 75/29 which may be viewed at this link.
Power: EU Models - 48.5 DIN hp at 7,500 rev / min
Final drive ratios: 15/36, U.S. and Canada continued with 16/40
Painted parts: Tank, side covers
Colours (varied by market):
- Black (Suzuki paint code 019) (with gold trim lines on the tank)
- Candy Turquoise/Hawaii Green (Suzuki paint code 215) (with gold trim lines on the tank)
- Candy Orange-2 (Suzuki paint code 00Z) (with black trim lines on the tank)