Sorry I am late with this, but here is a little tech info on the bike in question.

The RC148, used in the GP of Japan 1965, had the same bore and stroke as the RC 114, 33 x 29 mm, but the new RC149 gets the same dimensions as the RC116: 35.5 x 25.14 mm.

The crankshaft has a special configuration: the three cylinder part has the crankpins at 120 degrees, the two cylinder part has the crankpins, in the usual Honda fashion, at 180 degrees. Both crankshaft are coupled together at the position of the camshaft drive.

The valve angle is 56 degrees, 24 degrees for the inlet and 32 degrees for the exhaust valves. Lubrication system is by wet sump, with two oil coolers in the sides of the fairing.
There's also an oil temperature gauge. The oil temperature is checked, and the coolers can be covered more or less to maintain the oil temperature within certain limits

Power output is 38 bhp at 20,500 rpm. If you're surprised that this is not 21,500 rpm, just like the RC116 : the complicated crankshaft reduces the mechanical efficiency somewhat, which results in a slightly lower Pme of 15.5 kg/cm2 and a 1000 rpm lower engine speed for maximum power. The polyester petrol tank has an unpainted strip, to check the petrol level.

1965 - The 125 cc class is a total disaster this year.

Honda start the season with last year's 2RC146; they retire in Germany and Spain and end up down the field in France. On the Isle of Man, the 4RC146 makes its debut. Taveri comes in second in Man, the best place of the season(!), and comes in 5th in Holland. In East-Germany and Czechoslovakia the Hondas don't start, in Ulster Bryans finishes 4th, in Monza again no Hondas. In the last GP of the season in Japan, the new 5 cylinder 125 cc is unveiled, and though the bike is streets faster than the Suzukis, Taveri has to retire with an oil leak while leading

1966 - In the 125 cc class, the competition for Honda this year comes from Phil Read and Bill Ivy on Yamahas, not from Suzuki. Taveri takes the title, with Ivy second and Bryans third. The manufacturers' title goes to Honda, with Yamaha second and Suzuki third.