Kawi2strokes.com Forum

Bought an incomplete Bridgestone GTR engine recently and it's interesting to compare the GTR and A7 engines. Basic specs are similar: 350 cc two-stroke twins with horizontally split cases, disc valves and oil injection, introduced for 1967 model year.
Initial impressions: the GTR is more sophisticated, with a SIX-speed gearbox and a dry clutch, and aluminium cylinders with chrome-plated bores. Weather protection for the GTR's generator is non-existent, however, compared to the A7's. The GTR developed 37 hp, the A7 40 hp initially, later 42 hp. The GTR's exhausts are retained by two studs and nuts which is a better solution than the A7's system of a screw-on collar.
Both are dead easy to work on, though the GTR requires a special spanner or two to remove the clutch. The GTR's crank pinion nut has LH thread, a nice touch.

StoneBridge will accept the 1:1 ratio CDI A7 alternator housing, bolts right in, use the BS gear on the A series shaft. There are two different A series alternators, one runs i:1, the other runs half speed. MUST use the 1:1 ratio alt. MIGHT, never tried it, but might fit direct A series CDI pickup and reluctor/rotor into the BS alt.

I have 5 GTR/GTO bikes, two each low and high pipe Hurricane 175's, and 1 each Sport 90, Mountain 100. When the jetting and timing were spot on in the StoneBridge, they were just a touch faster than an A7, both had equally dismal brakes.

Not many people know that Bridgestone had a couple of prototypes, air cooled 3 cylinder, rotary valve two stroke bikes. Yes, I said rotary valves on all 3 cylinders. Clever two piece valve on the center crankshaft. Although hey have never been found, those two prototypes, and a whole bunch of other BS casting molds and machining fixtures for the twins and singles are supposedly stored some place in Chiba, Japan, where the last bikes were built.

would love to see a picture and also of the Olympus 370cc triple

Sounds very similar to the MZ 125 triple which was being developed in the 1960s- Motorrad Classic wrote an article about the engine in 1994. The triple was abandoned due to lack of power and perhaps also because of the FIM's new rules limiting 125s to a maximum of two cylinders which would have made the engine redundant anyway. The MZ was, of course, water-cooled.
MZ introduced a 125 tandem twin in 1970 but this was not successful and rarely raced, though Kawasaki used the layout for the KR250 and 350 a few years later, as did Rotax.