UK Ducati 250 mk3

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Samurai
Posts: 72
Joined: Wed Nov 28, 2012 9:53 pm
Location: Somerset, U.K.

Re: UK Ducati 250 mk3

Postby Samurai » Sat Jul 21, 2018 8:01 am

To tell an Italian made Ducati from one made under licence in Spain by Mototrans, look at the engine number. If it starts DM it is Italian (Ducati Motore) but if it is MD it is Spanish (Mototrans Ducati).

Beware as not all engine components are interchangeable and ignition systems may differ.

There are guys on here who will know the exact differences though and I'm sure one will be along soon to help :D

ducwiz
Posts: 266
Joined: Tue May 22, 2012 12:52 pm
Location: near Frankfurt, Germany

Re: UK Ducati 250 mk3

Postby ducwiz » Sat Jul 21, 2018 8:24 am

Well,

if it is a spanish made engine, it would have been equipped with a Motoplat ignition/alternator (which is known to produce a weak spark and to fail often). Also, the oil pump drive gear, idling between crankshaft and points shaft, is made from plastics and is known to wear or fail prematurely.

..

Scottish888
Posts: 27
Joined: Wed Feb 07, 2018 1:47 am
Location: Scotland

Re: UK Ducati 250 mk3

Postby Scottish888 » Mon Jul 23, 2018 12:47 am

Its an Italian engine, stripped the top end off today to see the state inside.
Discovered the crankpin (big end) has a lot of play. (maybe the most expensive part on the bike?)
The piston had the number 74-65075/3, is that standard or oversize?
So re-assembled all to avoid parts getting lost in my garage. Will have to leave this bike as a non runner for now.
Will try and find a good used crank in the meantime.

Regards

Bevel bob
Posts: 764
Joined: Thu Apr 15, 2010 8:01 am
Location: Bromley Kent UK.

Re: UK Ducati 250 mk3

Postby Bevel bob » Mon Jul 23, 2018 3:00 am

Hi,there will be lots of sideplay on the rod but any up down it is fooked. A secondhand crank is likely to need an overhaul so it would have to be really cheap to be worth the risk ,and if cheap you have to wonder why. Alpha bearings are closed I think following the death of owner.

Samurai
Posts: 72
Joined: Wed Nov 28, 2012 9:53 pm
Location: Somerset, U.K.

Re: UK Ducati 250 mk3

Postby Samurai » Mon Jul 23, 2018 6:11 am

Oh well, another bike that 'was running fine when I took it off the road 20 years ago ' then :D

Jon Pegler
Posts: 241
Joined: Sun May 16, 2010 6:19 pm

Re: UK Ducati 250 mk3

Postby Jon Pegler » Mon Jul 23, 2018 7:30 am

Whilst I suspect that your 250 Mark 3 is certainly an Italian machine, Samurai is not giving you correct information regarding engine numbers ,continuing to repeat a popular myth.
ALL Spanish widecase engine numbers start with the pre-fix DM, so just because your number says DM 250 is no guarantee that the motor was made in Bologna.
Narrowcase Spanish engine numbers do have the MD pre-fix, as do most, but not all Spanish widecase frames.
Sometimes the engine number sequence itself will indicate a Spanish motor. If the number starts 114... 115... or 116... it is Spanish built.
Bear in mind that quite a few of the motors in 250s and 350s that came out of the Bologna factory at the end of the production run in 1974/5 were made in Spain.
All the motors built in Spain and supplied to Bologna came with 'Made in Italy' cast onto the timing cover, just to confuse potential owners.
The last singles built came out of the Mototrans factory in 1982/3. Their timing covers finally had 'Made in Spain' cast into them.

Jon

ranton_rambler
Posts: 135
Joined: Sun Jun 04, 2017 11:33 am
Location: Stafford UK

Re: UK Ducati 250 mk3

Postby ranton_rambler » Mon Jul 23, 2018 8:32 am

I would say (from my limited experience) that unless you know the condition of the big end is good, it is absolutely necessary to split the crankshaft. Mine didn't feel too bad but once apart it was apparent that water had got in whilst in storage and the bearing surfaces were damaged. All is fixable at a cost of course.
In my case, as it's a 175, finding a good con-rod kit was very difficult. In the end I bought a donor 250 rod and had it re-sleeved to take one of Nigel Lacey's bearings. 250 is same length but with a bit more material to play with. Nigel stripped and re-assembled for me as I know my limits. Alpha did the work and made a new crankpin, but as said above, Max died suddenly so not sure if they will continue. Nigel has 250 rod kits I think. Very nice, but priced accordingly.
I think you said somewhere in the start of this thread that you wanted to save some money. If so, you'd better sell your Ducati and get something else. These little bikes are an excellent way of spending money!
Ian

Scottish888
Posts: 27
Joined: Wed Feb 07, 2018 1:47 am
Location: Scotland

Re: UK Ducati 250 mk3

Postby Scottish888 » Mon Jul 23, 2018 9:29 am

Thanks for the advice folks,

I will check around for a new crank pin/bearing set, hopefully there will be a few sources.
I know that Ducat parts are not cheap but you always hope to be lucky when you buy.
Will concentrate on the other parts of the bike that need renovated.


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