I am rebuilding a 1973 Mototrans 250 NC scrambler ( I know, please don’t mock the stupid ) and have to get the camshaft and rockers reground due to exessive scoring caused I suspect by low oil feed to top end. What I need to know is the cam timing ( inlet and exhaust valve opening closing periods ) for this engine so I can let cam grinders ( Pipers or Kent Cams ) know what profile to grind the cam to…
If you personally do not know, can you suggest someone who might be able to help, or possibly be able to sell me some servicable used parts.
I have had a look in a couple of places, the workshop manual for the narrowcase singles and Mick Walkers book “Ducati Singles”
For the 250 scrambler Mick says :
inlet opens 32degrees BTDC
inlet closes 71 " ABDC
exhaust opens 50 " BBDC
exhaust closes 44 " ATDC
The workshop manual varies slightly with 32, 75, 55 and 44 but does give a variation of +/- 5 degrees.
I am not an expert, just read a book, but hopefully of some help.
I also assume that Mototrans continued with the same spec for the narrowcase engines after the rest of the world went widecase.
Thanks very much for your reply. I also have Ducati workshop manual and Mick Walker’s book, but the Ducati 250 engines were all 74mm bore and 57.8mm stroke wheras the Spanish engine has 59mm bore and 66mm stroke for some strange reason. They also had smaller inlet and ex valves, so I would assume the cam duration is not going to be similar to any of the proper Ducati’s.
I am sure that somewhere on a forum I have seen someone make reference to a person in the UK that knows about the Spanish engines, it would be great to know who it is.
I have spoken to a lot of Ducati single owners, and very few realised that the Spanish engines are so different, although externally appear to be similar visually.
I will keep fingers crossed that someone can help.
This might be of some use perso.wanadoo.es/kombo/ - it has the cam timing hidden in the technical section and the translations a bit wacky, but the info’s there. Have fun…
John - it might be worth looking on facebook for a guy called John Wittman, he has quite a bit of knowledge re the singles (Spanish and Italian). Likewise, I think Lance Johnson may be able to help …