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I have a 1964 Mach1S (0007) that I got in in 1971. There are some pictures of it in Ian Fallon's recent book on Ducati singles. It came with the correct 30mm SSID carb and I never had any clearance issues with the tank (which doesn't have the modifications that have been mentioned earlier). I have no reason to think that the tank was not original to the bike. For routine use I've mounted a 32mm pumper which is a bit large so I've raised the rear of the tank for clearance.
So I think Rick is spot on with respect to carb size. Maybe those modified tanks were altered to provide clearance for other carbs?
Phil

Rick wrote:The SSI 27 and 29 are both made from the same casting - the 25mm SSIA through the 30mm SSID are the same physical size ...

bikester250 wrote:I have a 1964 Mach1S <snip>. It came with the correct 30mm SSID carb and I never had any clearance issues with the tank (which doesn't have the modifications that have been mentioned earlier). <snip>

Thanks Rick and Phil. That information is an important correction to what Falloon's states. This is what he says on page 125 of his Book, here describing the 1965 250 Mark 3:

"... and the engine included the ... larger SSI 29mm carburettor <snip>. As the carburettor was now larger, the fuel tank was modifed underneath to provide clearance."

Good stuff ...

Here's a pic of my 1963 250 MK3 with. 27A SSI carb. The asymmetrical tank is required to get the clearance required for the SSI carb to fit. The other photo is a side by side of the 250 Diana and 250 Diana MK3 tanks. The non MK-3 Diana has a UBF24 carb and does not require the asymmetry to fit. MK3 tanks is on the left. Both of theses tanks are 4.5 Ltr tanks which were only used on the 4-speed Diana and Diana MK3. The later 5-speed Diana's and Mach1 had a 4.2 Ltr tank with a different cutout than the 4.5 Ltr MK3 tank. The 4.2 Ltr tanks are noticeably narrower. Anyways, that's the way I heard it!

IMHO Anthony got himself a 4-speed 250 Diana, not a MK3, but a nice project nonetheless!

Tom Bailey does a nice job with some more details and photos in his books on the early Diana's.
Tony

Thanks Tony - good and clear.



Any particular reason you think Anthony's bike might be a 4-speed? (I kinda assumed he'd know ... )

My TS tank has a different cut-out on RHS - needed to clear the top of the MB22 carb.

Presume tank capacities mentioned are gallons? My book says TS tank is 18 litres, which is 4 proper UK gallons. I think it would be 4.8 US gallons.

My reason for thinking it was a 4-speed is that all the info I have suggest 5-speed engine numbers started 9xxxx and 4-speed engines are 8xxxx. The other reason is that the 4-speed DM250 stamp is on the shifter side and for 5-speed the DM250 stamp is on the kicker side.

Anthony's engine has the DM250 stamp on the kicker side and is 8xxxx. Anthony can you verify that there indeed 5 speeds/gears? Thanks.
Tony

Hi Tony

I have a video of me shifting through the gears but I'm not sure exactly how to upload it could i email it to you?. Im up in Pebble Beach having a look at this Mach 1 not to purchase just to see how it looks.

IMG_3460 by pink.anto, on Flickr

IMG_3455 by pink.anto, on Flickr

IMG_3449 by pink.anto, on Flickr

IMG_3446 by pink.anto, on Flickr

IMG_3445 by pink.anto, on Flickr

ranton_rambler wrote:Presume tank capacities mentioned are gallons?

Very glad you're here to correct our stupidities, Anthony! Yes, of course . Caption to previously posted photo now corrected .

Here are the figures taken from assorted owner's handbooks (calculated down to the 4th decimal place by Ducati, note ):

Diana and early GT: 17 litres = 4.4904 US gallons = 3.7397 imperial gallons
Mach 1 & Mark III: 16 litres = 4.227 US gallons = 3.5196 imperial gallons
250 Monza and late GT: 13 litres = 3.432 US gallons = 2.8597 imperial gallons
Scrambler: 11 litres = 2.9059 US gallons = 2.4197 imperial gallons

Mr Pink,
Very nice example of a Mach 1. I am a little curious about the high gloss silver paint on the bike. From my memory the silver paint on the original bikes was semi-matt or matt finish paint. I was never around when one was pulled out of the crate but the original bikes I have seen were not high gloss.

Chuck

Hi Chuck not sure about the paint to be honest but this one is definitely very glossy.

I purchased the Ian Fallon book and from what i can tell it wouldn't be out of the question for me to restore this with clip on's, Blue tank and Black frame with normal footpegs.

Am I correct in assuming I should be looking for the scrambler front mudguard as apposed to the Mark 3 type?.

Front fork build date 1964
IMG_3015 by pink.anto, on Flickr

Borgo piston
IMG_3331 by pink.anto, on Flickr