ID this bike model?

[blaat!]

Bought this six months ago. I'd like to get your opinions on what this thing really is. Go easy on her... she's been though a lot. The bike sat in the seller's garage since the mid 90's. He saved it from going into a scrap pile. It was in a condemned building that was going to be torn down. He had plans of restoring it, but just had more sense than me.

I'll try to put in all the relevant details. I can post more photos or look closely for you if there are more details needed. Just let me know.

The day I brought it home. It had race wire on some of the engine bolts. I have scrutinized the frame very closely, and there are no serial numbers on it. None on the head tube and none on the spine near the battery tray.

side-view.jpg

The engine numbers appear legit. When I bought it the engine had decades of dust and grime on it. If there is any chance the numbers were faked, it was a long time ago. The DM250M1 is centered in the space, so I don't think the "M1" was added later.

engine-number.jpg

The forks have a '65 date on them

fork-year.jpg

A picture of the head tube. Headlight bracket welded on.

frame-1.jpg

The triple tree seems to be a street/clip on version (with holes added later - for cables maybe)

ttree.jpg

reached the five pic limit...

[blaat!]

The inlet valve is 40mm and the exhaust is 36mm.

There is no paint color code left on the cam. The largest dimension of the cam lobes:

31.34mm
32.03mm

cam.jpg

The piston is stamped "Borgo 74 65075 61?"

piston.jpg

Front wheel.

front-wheel.jpg

Scrambler style side stand?

side-stand.jpg

Rear shock.

rear-shock.jpg

The kick starter is not curved. The shift lever was cut to remove the heel portion. Some of the parts may have been replaced or swapped out? Feel free to offer up your expert opinion, or maybe we can all just make up pretend stories about the history of it

Thanks!

[Eldert]

the engine looks like a Mach1 to me . the numbers are correct

i compared the camshaft to a Mach 1 cam i have and it is the correct camshaft . colorcoded GREY

the piston look like a factory race item , never seen one like that .

Eldert

[Rick]

Just an observation- not an opinion- the 'M' from the 'DM' is a different stamp than the M on 'M1'. I bought 2 M1 engines last summer and an M3 engine, my M1 engines use the same stamp in both instances, but the M3 engine has mismatched Ms like yours- my M1 serial numbers are much lower than yours also.
Maybe at some time during the run of these engines Ducati had a single stamp made that was a complete 'DM', and used the individual stamp for the M on M1. My widecase stamp is the DM stamp like yours and my M3.
If the theory is that real M1 engines should have the stamps centered in the case because the entire M1 stamp was done at the same time, then using 2 different M stamps would be curious.
Rick

[AIRMANBLUE]

It looks very much like the remains of a Mach 1 The piston is the standard race Borgo giving 10 -1 Compression ratio .

[Bevel bob]

Looks like an old race bike to me, modified head to take Amal carb? I would rebuild as a Mach 1 ,Elderts comment on the piston is interesting ,I have the same piston in my Mark3 , I thought it was a standard one, what ratio is it likely to be??.

[Eldert]

here is a pic of the 74 mm 10 to 1 Borgo piston
when measuring the combustionchamber with fluid and doing the math i never got 10 to 1
9.3 to 1 is what i landed up with



Eldert

[double diamond]

The engine looks to be a believable M1. That’s a really late number though. With the fork slider year marking, it would make it a pretty early chassis for a Mk3. Are the hubs 7 fin or 3 fin? Rear sprocket drive plate has the six reinforcing ribs or if it’s the smooth type? The front speedo drive plate doesn’t appear to have the cast in air scoop. All this leads me to believe it has the 7 fin hubs, which makes it an earlier chassis. Also, it doesn’t look like a Mk3 chassis to me: Monza type tool box mounts, no rearset footpeg bungs. If the brackets for the rearset brake cable attachment and brake light switch are missing on the left side, this would also be an indicator. The rims look more like the heavier Monza type rims but hard to say. Can you read the rim manufacturer stamp? Definitely race tires though. Smooth fork crown and what appear to be original Ducati clip-ons. Shocks look like Monza type with shrouds removed since there are no plastic covers under the springs. Some things look like early Diana or Monza, some like Diana Mk3 but unlikely that engine was originally installed in that frame. MW

[blaat!]

Thanks Double Diamond and everyone.

Looks like seven fin hubs.

rear-hub-ribs.jpg

Are these the six reinforcing ribs you mean?

rear-hub-inside.jpg

Another image of the frame. Rear loop and battery tray have been modified.

frame-2.jpg

Close up. The bracket for the rear brake and cable was home-made... I removed it.

frame-close-up.jpg

No way to read the rim mfg stamp... too much rust. I think it spent the later part of it's life as an outdoor bike.

Close up of the clip-ons.

clip-ons.jpg

What does all this mean? Mach 1 engine put into some other frame to race? Any other possibility?

[double diamond]

A few more details on the frame: no reg/rect mounting plate under the seat, no rearset hardware, no horn mount which would be on the backbone right above the engine mount/in front of the battery box. Of course all this hardware could have been cut off (looks like the original footpeg splined mounts have been lopped off), but I suspect it’s probably a Diana Mk3 chassis. It has the smooth crown, clipons and campagnolo hubs, might be butted spokes? The ribs I previously referred to are on the cush drive plate the sprocket bolts to. They’re in the dished area between the sprocket flange and the axle seal. The campagnolo type don’t have them, later Grimeca hubs do. MW