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Hello, my name is Davi, I am new here and trying to navigate my way around the forum so please forgive any initial screw ups. I am also new to Ducati engines but have rebuilt many motorcycle engines over the years. I am currently helping my brother rebuild a narrow case 250 which has loose rollers around counter shaft first gear. The problem is that the outer race which is staked into the left case is damaged. The engine was stripped by someone over 40 years ago and they knocked out the race and damaged it, so my first question is, what are my options here? Am I going to be looking for another case half, was there any modifications done to replace this with a ball bearing or can a race be made and bonded/staked back into position?
Thanks in advance for any feedback.
...... Davi.

Hi, it is disappointing that nobody here has managed to answer your query, I certainly can't.

If I understand correctly, your engine has a bearing race fitted into the crankcase and rollers running directly on the counter shaft? Cannot the bearing race that is damaged be simply replaced with a new one, or is the housing damaged? Possibly the best option is to find a deep groove ball bearing that will fit the shaft and have the crankcase housing either sleeved or machined to fit.

Please keep us informed.

Hi
The outer bearing race is a Ducati specific part and unfortunately pretty impossible to find NOS, even good used is hard to find. I did have a couple of batches made over the years, but unfortunately a new batch has not been instigated yet. I do plan to have a new batch made, but that most likely won't be available until later in the year.

The reason it would be difficult to replace the roller with a ball race is the rollers sit in a groove behind the kickstart ratchet gear on first gear. If you were racing and didn't need the kickstart then it might be possible to utilise a ball race, by grinding the ratchet off. There is not enough material in the casing to fit an oversized bearing and therefore there is a very thin available annulus to work with. The Mototrans 5 speed engines use a thin needle roller instead but as the Italian first gear is grooved deeply behind the ratchet, that would not be possible without maybe using Mototrans gears or gearbox as well. As the gears are different ratios you would probably have to change most or all the box to accommodate the this roller. I have fitted Mototrans gearboxes to Italian engines and visa versa, so it is possible, but it would be far easier and better to sort a proper replacement race.

Hope some of this helps.

Regards Nigel

Is your engine a 4 speed or 5 speed?

Davi (the OP) said he had a staked in loose roller. Only the 5 speed narrowcase engines have the loose roller arrangement, all the 4 speed engines have a deep groove ball race. The roller arrangement was I think a work around to increase the kickstart ratchet diameter.

Nigel

Indeed, the early 4 speed engines used a ball bearing in the location under discussion. These engines are identified by the engine serial number being stamped on the left engine case and DM250 stamped on the right. I don’t know about the GB market models, but in USA market there was a later version of the 4 speed that employed a roller bearing, similar but not identical to the 5 speed design. These engines are identified by the serial number stamped on the right center case and DM250 stamped on the left. If the subject engine is one of these late 4 speeds, it may be possible to convert to a ball bearing to resolve this issue although it would require replacing additional parts.

I would like to thank everyone who has replied to my post, I will have a lot to learn about this engine but the archives here and the knowledge you folks possess will I’m sure see this project through to the end.
Nigel, if you were to have a batch of the races made I would definitely take one off your hands, whether or not I can obtain a race determines if the build is going to happen but it has been apart for over 40 years so another few months is not going to make any difference. My next move will be to get the appropriate Workshop and parts manuals
......Davi.

Hello Davi
I'll keep you posted on progress.
Regards Nigel

Hello Nigel, it’s been a while since I’ve been here and my brother’s project is still ongoing, did you ever get a chance to get a few of the case races made?
.....Davi.

Hello Davi

Sorry still on the back burner, made worse with supplier/manufacturing issues related to Covid. Unfortunately some old and trusted manufactures have taken a turn for the worse with staffing/skills issues. Over the last year some older generation skilled workers have taken the decision to retire early.

Moving on I do have a firm in mind to make these, but my time is limited to get new products drawn up and into production. Also we have been experiencing longer lead times from many companies.....Anyway I'll take this as a nudge and I'll do my best. I am however tied up at the moment trying to get a batch of Narrowcase rod kits for road bikes underway, that's been a pressing issue for a few years now.

Regards Nigel