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Discussion Starter #1
Hey folks! Picked up a duc 250 (po says the motor is a 450???) single. My question is, is this a desmo...ie valves mechanically opened/closed...no valve springs? Heres some eye candy... :D

 

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Nice score! In spite of the 250 decal on the cover, what you've got there is a 450 (maybe a 350). Look at the small cover on the cam, it will have the cc there. Your's probably is a desmo, however, you can just pop off a valve cover to check it. If it's a desmo, the word desmo will also be on a cam cover.

I have three Ducati singles, two 250s and a 350, all of which are pre-desmo engines with 'hairpin' valve springs.

The older singles, like mine, are called 'narrow case' singles, yours is a later, 'wide case' model.

The Ducati engine is truly a work of art and makes most everything else produced at the time seem primitive by comparison. Be sure to get a manual before doing anything more than simple maintenance. The engines are works of art, you can't just tear into them like you can a Triumph. Before trying to start it, change the oil. The filtering system on the Ducs is very primitive and if you let the oil get dirty you'll soon be lunching big-end bearings.

There's lots of good info out there.

Have fun.
 

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rad! i've had a couple duc singles... a desmo and a pre desmo. man, i dig the things. looking for a desmo 350 or 450 project right now.

the engines really are works of art. such rad motors and so much fun to ride... really miss the last one i had.

that one looks like its in decent shape. post more pics!
 

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Discussion Starter #6
@glider Then the PO was not lying...he said the engine was a 450. I went out this morning before work and indeed it does say 'desmo' on the left upper side cover on the head, though it was almost worn off for some reason.

Yeah, I think it was a pretty good score. For 1200 smacks I got the complete bike plus another frame (for a single, but not sure if 250, 450...) and a 250 bottom end and a bin full of misc parts. My plan is to get the bike running in its current form, and work on collecting a top end for the 250. If I can ever cobble together the parts to complete the 250 engine, then I'll swap out the 450 to bring the bike back to original form.

Anyone have any top end 250 parts they are willing to part with? I have a titled frame I would consider trading for it.
 

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Yeah, I think it was a pretty good score. For 1200 smacks I got the complete bike plus another frame (for a single, but not sure if 250, 450...) and a 250 bottom end and a bin full of misc parts. My plan is to get the bike running in its current form, and work on collecting a top end for the 250. If I can ever cobble together the parts to complete the 250 engine, then I'll swap out the 450 to bring the bike back to original form.
Does the frame have ribs welded on it? Hard to tell from the pic but it almost looks like it might. If so, it was a 450 from the factory. It wouldn't surprise me if it's the sidecovers/decals that were changed rather than the engine.

As Glider said, get a manual before you tear into anything on it. There are shims everywhere in that engine and it's easy to lose one or forget where it goes. You can of course re-shim them but it's added work. As for the top end on the 250 - keep in mind the bevel gear sets are matched. Taking a gear from this cam and pairing it with a gear from that tower shaft makes setting the mesh less than trivial.

When you're trying to get the 450 running, realize that the timing marks only line up once every six revolutions. A degree wheel is your friend on these things. If it "ran when parked" you can probably assume everything is timed correctly, but the best course of action is "Trust but verify". There is a slight chance someone has timed the cam on it by messing with the gears. When that happens... the timing marks aren't correct anyway. If the cam gear has a stepped key proceed with caution and trust only the degree wheel. I say it's slight chance but one of my bikes ('74 750 twin) is set up like this. Heaven help the next owner if he trusts the timing marks.

Again, get a manual. Look it over before tearing into the bike. For support there is a bevelhead mail list (micapeak.com). It caters more to the twins but there is a huge amount of single cylinder experience/knowledge there too. There is also a singles website at motoscrubs.com. www.ducatimeccanica.com and bevelheaven.com both have literature online.

Nice score BTW. I prefer the narrowcase bikes but any Ducati single is fun to mess with.
 

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Discussion Starter #10
@desmodog The PO seemed pretty confident that the bike is all 250 with a 450 shoehorn in. He mentioned more than once that you could tell by how close the top of the motor is to the backbone. It has an inch or two clearance...but I have not seen a 250 so I could not judge.

I was not planning on tearing in to the 450 that is in the bike now. It turns over, so my plan was to change the fluids, clean the carb and give it a few kicks and see what happens.

Thanx for the links...there does not seem to be a 'singles only' (ha...would be a good name for a website dedicated to these bikes) forum anywhere.
 

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...there does not seem to be a 'singles only' (ha...would be a good name for a website dedicated to these bikes) forum anywhere.
There is...

http://www.motoscrubs.com/forum/index.php

EDIT: Sounds like a plan on getting the 450 running. I've just seen a lot of messages from new owners claiming they have to pull the head because the timing marks don't line up, etc...

I'm not very familiar with the widecase frames but on the narrowcase bikes the same basic frame was used from 160 to 350. A 350 will fit in a 160 frame (all bets are off on if the tank will still fit). Point being, I don't think the head on a 450 will be any farther away from the backbone in a 450 frame than it is in a 250 frame. But again I'm not all that familiar with the widecase stuff. I'm 99% sure that the 450 frames were the only ones with ribs welded on though. So... ribs = 450 frame, no ribs = not a 450 frame.
 

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There's a very good Ducati site out there that has a section devoted to the singles, lots of good info there and lots of inspirational pics. Do a search for Bevel Heaven.

If the bike has a compression release, be sure to use it. You want to bring the piston past TDC on compression before kicking, unless you want to get kicked!

If you get it running change the oil right away. There is also an outfit that makes magnetic drain plugs for them--definitely a good idea.

Also check for a charge at the battery. One of the weak points of the singles is the electrical system. Fortunately, there are now nice electronic rectifiers and other good stuff for the bikes.

You'll probably find that the engine needs little more than a carb cleaning and tune-up, they're pretty bulletproof.
 

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I had a '65 250 Scrambler and starting was really improved by a special coil. This was in 1980, so I don't remember any useful details, but at least it's a clue.
 

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Discussion Starter #17
...the bike looks like it has been rewired at some point. The wires don't look stock to me. Additionally the coil looks to be aftermarket. The wiring looks very clean, so I'm hoping its a quality job. If the Arctic winter ever ends I may post some details pics.
 
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