Desmonto (sp?) engines

[Blakamin]

mercedes used it too... waaaaay back.... a cool history

[Biff]

Yeah thats all fine .....but y do u want to no about desmo??

I just do. I'm that kinda guy.

[Kickaha]

more maintenance than normal valve????
Not really, on the fuel injected models, you have to check the valves after 10 000 km, it's a little tricky thats all - for a good mechanic - no prob

Kiwi

The Darmah used to work out at 10,000km as well at about $300 a time,mainly due to the fact you had to drop the motor to acess the rear head

As Paul pointed out, many Desmo race engines also have springs in order to assist the engine at slow RPMs. In addition these low compression springs also appear to be used in order to assist with 'chatter' and to ensure that the valves seals are tight at very high engine RPM's.

On the real desmo bikes(bevel drive) several race tuners used to toss out those springs as they didn't believe they did anything at high RPM and that they were there to help valve closure at low rpm only.

Yeah thats all fine .....but y do u want to no about desmo??

Maybe he's going to sell the Blockbird and buy a real bike

[Blakamin]

On the real desmo bikes(bevel drive)....

oi.... mine is the same... just has rubberbands... it's the only difference really...

[Marmoot]

oi.... mine is the same... just has rubberbands... it's the only difference really...

mine got gear-drive for the cams. So are CBR250s
Saves a lot of $$$ compared to those cambelts apparently

[Biff]

Maybe he's going to sell the Blockbird and buy a real bike

And you'd know about owning a real bike would you? I mean that pre-war monstrosity that you ride about on and the bastardised carcasses of fifteen others that lay around in your gargre really show that you’re the man in the know when it comes to ‘proper bikes’. Rightbackatcha you bitch.

[speedpro]

Sounds like Vtec in a Honda but obviously worked out and utalised better

Actually they have nothing in common except that valves open and close.

[speedpro]

Thanks for the info' guys. Here's what I've managed to find out in addition to the info' you've kindly posted:

Race spec Desmodronic engines are notoriously fiddly to set up and maintain. This is in addition to the fact that they appear to be very expensive (Although you can apparently convert a GXR1000 to a Desmo engine for around $8000) and require regular, specialist servicing in order to ensure that the cams responsible for opening and closing the valves are in sync. Otherwise all manner of nasty things can take place. Apparently the Ducati engines used in races demand a total rebuild every couple of hundred K's, while Suzuki's and Honda's that were based upon Desmo' engines lasted for a couple of thousand K's. I'm not sure why this is, I'm just repeating what I've just read.

As Paul pointed out, many Desmo race engines also have springs in order to assist the engine at slow RPMs. In addition these low compression springs also appear to be used in order to assist with 'chatter' and to ensure that the valves seals are tight at very high engine RPM's.

It is apparently not recommended to simply convert and engine to a Desmo, without fitting lightweight piston rods, preferably to Titanium ($3000 each!!! Thankfully most Desmo engines are twins). In addition, it's also recommended that the piston heads are changed for lighter weight variants.

I'd better point out that all of the fluff I've just written appears to apply only to race spec' bikes, and not road going variants.

Thanks again for the info' guys, and please keep it coming.

For some reason this reminds me of 'old wive's tales'. Stuff being done but the REAL reason is lost.

[moko]

Interesting bit here about the inventor of Desmo valve-gear,apparently a pom who originally tried it on a Triumph,good example of "what if" there as they would have been years ahead of Ducati and if it had worked better Desmo-valved bikes might well have been the norm.
http://speedwaybikes.fortunecity.net/desmo.htm

[Biff]

For some reason this reminds me of 'old wive's tales'. Stuff being done but the REAL reason is lost.

All the information came from official Ducati sources and engineering journals. So what are you trying to say exactly?

[gav]

What do you mean by converting race engines to desmo, all Ducatis are desmodromic, you don't convert them to a desmo to race. Well certainly not in the last 20 years.

[Blakamin]

Interesting bit here about the inventor of Desmo valve-gear,apparently a pom who originally tried it on a Triumph,good example of "what if" there as they would have been years ahead of Ducati and if it had worked better Desmo-valved bikes might well have been the norm.
http://speedwaybikes.fortunecity.net/desmo.htm

thats what ducati say too... a lot of people used it before ducati... but ducati did it so it worked.... and stuck with it.... it actually looks like Arnott has a spring in his valve stem tho.....

1910
Arnott, from England, realized the first desmodromic timing system: a "shaped annular cam"moves a rocker arm.

Arnott below


a bit different from the duc design in 1968 to today (2 valve)


(this is a bevel, but the only difference is the drive)

[moko]

[QUOTE=Blakamin]thats what ducati say too... a lot of people used it before ducati... but ducati did it so it worked.... and stuck with it.... it actually looks like Arnott has a spring in his valve stem tho.....

Point taken but you`d expect a bit of innovation 40-odd years later wouldn`t you? Post was intended as a bit of information,not a dig at Ducatis.
On the servicing point,they might well be fairly simple to service for a decent mechanic but try and sell one in Britain without full Ducati dealer service history and you`ll be lucky to find a dealer to take it in p/ex let alone sell privately.I know a bloke with a really nice (i.e. pampered and totally immaculate)600ss that he cant even sell at a giveaway price because of that,he dropped as low as £1350 which is tatty 600 Diversion money,no takers.another guy has a 600 Monster collecting cobwebs for the same reason.

[Biff]

What do you mean by converting race engines to desmo, all Ducatis are desmodromic, you don't convert them to a desmo to race. Well certainly not in the last 20 years.

If you read the thread again you'll note I said nothing about converting a Ducati to a Desmo. I did however refer to the price for converting a Gixxer.

[Blakamin]

[QUOTE=moko]

thats what ducati say too... a lot of people used it before ducati... but ducati did it so it worked.... and stuck with it.... it actually looks like Arnott has a spring in his valve stem tho.....

Point taken but you`d expect a bit of innovation 40-odd years later wouldn`t you? Post was intended as a bit of information,not a dig at Ducatis.
On the servicing point,they might well be fairly simple to service for a decent mechanic but try and sell one in Britain without full Ducati dealer service history and you`ll be lucky to find a dealer to take it in p/ex let alone sell privately.I know a bloke with a really nice (i.e. pampered and totally immaculate)600ss that he cant even sell at a giveaway price because of that,he dropped as low as £1350 which is tatty 600 Diversion money,no takers.another guy has a 600 Monster collecting cobwebs for the same reason.

what a waste... send them to me, I'll give them a good home!!!