Identify this bike

[DewCatTea-Bob]

[quote= KarstenH ...
" inlet Diameter is 29,2 mm "

____ I've never measured a Mach-I type in.port-diameter to be any less than 29.3mm !
So I'm suspecting that the in.port is not stock.
__ Can you post a close-up pic.shot of the intake-port's mouth & throat ?



" Valve sizes are 39,4/36 mm "

____ I've never measured a Mach-I type in.valve being so notably smaller than 40mm.
So that's another clue that the cylinder-head is-not (Italian)- factory-stock. _ How about posting a picture of the cyl.head's cooling-fin pattern around the ex.port-nose ?



" Number of teeth:
17/22/26/29/31
30/32/35/39 "

____ The 17t 1st.gear on the main-shaft is certainly same as a standard n-c.250 5-speed trans.
Is it's 43t mate completely missing (from the left-side case and-also your batch of loose parts as well) ?



____ If you had been forthcoming with what country this Duke you found was selling within, then I would-not have jumped to conclusion that it was a 'Diana 250', (as that model didn't come with a 5-speed transmission) !
If you found it anywhere near around Germany, then I'd more-so suspect that your Duke may be a hybrid-combo of Italian & Spanish Duke-parts.
If that's pretty-much what you actually have, then perhaps fellow-member Eldert can offer some clues as to what's-what, (as I've gathered that many Mototrans motors can oddly be rather strangely inconsistent compared to the Italian-made versions [and-so might possibly also oddly display motor-numbers which don't directly correlate to the very-same years of manufacture as the Italian-made motors]).


Duke-Cheers,
-Bob

[KarstenH]

Hello Bob,

i have make a mistake!!
My caliper was broken, it has had an offset.

The inlet diam. is 28,5 +/- 0,2 mm - that means i could be a scr/mk3 head.
I have made some Pictures - the inlet is not portet out - i can see a lot of pittings from the casting process.

Img_2224 neu.jpg

Here some pictures from around head

IMG_2220.JPG

IMG_2219.JPG

IMG_2218.JPG

IMG_2217.JPG

I hope you can see the details.

Kind regards Karsten

[DewCatTea-Bob]

[quote= KarstenH ...
" The inlet diam. is 28,5 +/- 0,2 mm - that means i could be a scr/mk3 head. "

____ That in.port dia.size is 1mm smaller than that of a 'Mark 3', but it's the exact dimension for a stock 250-Scrambler/Mark-III cyl.head !
Stock valve-sizes should thus-then be 36 & 33mm.



" I have made some Pictures "

____ Thanks for all your pix !



" the inlet is not portet out "

____ The in.port does appear to be stock.



" I hope you can see the details. "

____ The pic.shots with the cavity-holes (of in.port & cam.tunnel) could have used more light shown within.
__ Concerning the close-up view-shot (of the camshaft's tunnel-cavity) I've included,, it required extra effort to attempt to bring the image of the cam out of the extreme darkness, so the quality of the cam-profile image obviously suffers poor clarity and-so rather appears sort-of fuzzy-looking.
If you care to intentionally create a rather purposeful pic.image of your cam's profile,, then besides having your camera-view more concentrated mainly upon the same reduced area of the cyl.head as I have done, be sure to also include some extra/additional light shown down-into the camshaft tunnel-cavity.
Also,, the cam-profile will appear more squarely distinct if you try to align the view-shot of your camera-lens more perfectly in-line with the camshaft's center-hole passageway. _ (The present pic.shot was obviously taken with the camera-angle set too high above the preferred line through the passageway.)



____ The cyl.head must be from a pre-1965 Mark-III, as the camshaft is-not a Scr.cam !
The cam's profile appears consistent with a Red color-coded Mark-III cam.model.
While your presented Mark-III cyl.head could possibly be as old as your motor-case, it's from a different Duke-model than your presented frame originated from.


Duke-Cheers,
DCT-Bob