Sport Desmo twin>single conversion?

If you need technical information or help with your parallel twin Ducati GTL 350/500 or Sport Desmo 350/500 engine - post your FAQs, comments & questions here.
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Vulpine2
Cucciolo - the Lil Pup
Posts: 14
Joined: Sun Apr 25, 2004 9:23 am
Location: Peak District, UK

Sport Desmo twin>single conversion?

Post by Vulpine2 » Thu Jan 30, 2014 8:19 am

Been reading the other threads about this so I thought I'd post up

I went to look at a 350 Sport Desmo late last summer - barn find, private import to the UK from Italy. Found it whilst tooling around EBay. . Not actively looking to buy, but aware of the model and it's reputation. 5 miles from my workplace and I'd never seen one in the metal - so how could I not go and have a look at it?
Especially as, like others here, I'd been wondering if you could slot in a single to replace that heavy twin and create a lightweight café racer. A widecase single would make it completely period.

So I went to have a look.
Bike only had 5000 miles on it. MPH speedo (and reflectors on the indicators) suggest it was intended for US though AFAIK the 350 version was Italian market only, never exported? Minor crash damage told its own story (dinged headlamp rim, scuffs to brake lever & n/s engine cover) and it looked to have stood quite a while (cracked tyres, rotted carb rubbers). Patina in spades. Astonishingly, it was even a runner.
A quick bit of measuring suggested that the engine mounts might even line up with a widecase...
Just as well it was cheap as I couldn't resist it after that.

One or two issues with the plan (drivetrain) but I'm now told that Phil Hitchcock did a similar conversion, featured in an Oz bike mag a few years back. So, it's possible.
I'll drop Phil a line but has anybody got any pics/further info?
Last edited by Vulpine2 on Thu Jan 30, 2014 8:49 am, edited 1 time in total.
Rob
900ss, 350 SCR
UK

Vulpine2
Cucciolo - the Lil Pup
Posts: 14
Joined: Sun Apr 25, 2004 9:23 am
Location: Peak District, UK

Re: Sport Desmo twin>single conversion?

Post by Vulpine2 » Thu Jan 30, 2014 8:44 am

Rob
900ss, 350 SCR
UK

ducadini
750 Sport [BEVEL]
Posts: 225
Joined: Sat Jul 31, 2004 8:54 am
Location: Antwerpen

Re: Sport Desmo twin>single conversion?

Post by ducadini » Thu Jan 30, 2014 1:29 pm

Yes, the engine can be bolted fairly easy in a SD frame.
At the rear, everything's the same.
At the front, You will have to make some special plates, as the space between the tubes is the same as the width of the engine-mounts but with a few cm between them.
I'm not really sure about the height though, since the 250 is the lowest : no problem.
I tried a 350 engine and the space between the cylinder/head bolts and the frame was critical, had to leave the washers off.
So a 450 could be a real problem (IIRC this one is about 5 mm higher).
Then there are some issues with the carburator that is going to be a thight fit.
You have to turn the wheels around to get the chain on the righthandside, chain is a bit of fiddling to get in line but nothing too difficult.
You'll have to improvise with the brake pedal, as the SD setup is a bit special and very difficult to mount on the left side.
You could leave the brake where it is, and fit a cross-over shaft for the gearlever.
I hope You found the Speedline-wheels, since they are the lightest.
Better look for a GTL set of wheels with alu rim and spokes.
You will end up with a rather heavy BUT beautiful single with a bit of braking-overkill :-).

I'm glad/sad I never took this project to the finishing level :-)

ciao
ducadini
Nego i ricordi peggiori
Richiamo i migliori pensieri

Vulpine2
Cucciolo - the Lil Pup
Posts: 14
Joined: Sun Apr 25, 2004 9:23 am
Location: Peak District, UK

Re: Sport Desmo twin>single conversion?

Post by Vulpine2 » Fri Jan 31, 2014 3:38 am

Hey Ducadini

Thanks for that - all good stuff

Be interesting to see how this goes. Plan A is to see how I get on with the SD to start with - tidy it up and, hopefully, run around on it this summer.
I do have a non desmo 350 single available so that's a good place to start- if it can be made to fit...

As always, not a short term project - I don't even have a shed to work in at the moment! Shed first, bike next?

It didn't come with Speedlines, it's got the later(?) alloys. They may be heavier but I like the look of them as they seem to suit the angular styling.
I do usually prefer spoked wheels - but those from the GTL have a drum at the rear so a different problem to the disc on the SD/GTV?

Phil is checking to see if he has any other photos of his 250 conversion as it was being done. Anybody know the month/year and mag it was featured in - be good to get hold of a back copy?

Cheers
Rob
900ss, 350 SCR
UK

Jon Pegler
Mariana
Posts: 32
Joined: Sun Feb 14, 2010 8:37 am

Re: Sport Desmo twin>single conversion?

Post by Jon Pegler » Tue Feb 04, 2014 12:58 pm

Have a look at the Mototrans Ducati Forzas and Stradas.
This was a 250 or 350 single motor in what was basically the Spanish parallel twin chassis.
They are a bit heavy as singles, compared to the Italian produced models, but they do handle very well.
Braking was taken care of by a disc at the front with the exception of the earliest Stradas.
Double disc set ups stop even better.
Plenty of photos on the web.

Jon

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