Engine ID

[frankfast]

Do all Dianas have a 'DM250M3' engraved on the motor - both 4 speeds and 5 speeds?

[ajleone]

As far as I known only the 5-speeds have the DM250 M3 stamp. The 4-speeds just have DM250. Someone else my know more of different.
Tony

[Eldert]

only the last Diana's with the updated kickstarter mechanism had DM 250 M3 stamped

Eldert

[frankfast]

So, I'm assuming that the cam, pistons, valve sizes and ports in the 4 speed Diana were different than the 5 speed Diana Mark 3 and in a lesser state of tune. The carb was also not the same. Correct?

[Eldert]

there where at least 3 diff Diana's with diff specs . the european Diana 4 speed with very mild camshaft and UBF24 carb .
and the USA spec 4 speed with the red camshaft and 27 SSI carb . the last Diana's had the Mach1 grey camshaft and 29 mm SSI carb .

Eldert

[frankfast]

Eldert - Do you know if the valve sizes and port sizes were the same throughout the different Diana models? And was the compression the same? Thanks - Frank

[double diamond]

US market (i.e. Berliner) early 4-speed Diana was same spec as the Monza: 37mm intake valve, 33mm exhaust, same compression as a Monza unless the kit piston was installed (see “Directions for the Overpowering”). The stock intake port was sized to match the ubf24 carb. There was a kit carb SSI27A with a manifold to fit this carb. The intake port would have to be matched to the kit manifold. The Diana MkIII 4/5 speed was delivered with the SSI27A carb, 36/33 valves and a 10:1 piston. These two are actually the only “Diana” models but Berliner advertising continued to confuse the subject by referring to the Mark 3 as a Diana in some ads. The Mark 3 has 40/36 valves, 10.5:1 compression and SSI29D carb with corresponding intake manifold and intake port. Matt