Ducati 450 Desmo rebuild

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For those not familiar with Ducati singles, the flywheel they used had a quite heavy brass rotor riveted to a steel hub, mounted on the crank with a taper but with no Woodruff key. The flywheel sits inboard of the primary pinion and the drive side mainshaft is supported by an outrigger bearing in the primary drive casing. I cobbled together some old bits to show the arrangement, from left: the side casing with bearing, the journal on which the bearing runs, pinion, flywheel, drive side main bearing and crank. Oil is fed from the oil pump through the end of the timing side mainshaft, through a centrifugal sludge trap in the timing side crank web, through the crankpin to lubricate the big end bearing and surplus oil is then fed into the drive side mainshaft and out through a radial hole in the primary drive pinion to lubricate the primary gears. The pinion is a light press fit on the mainshaft and is secured by a Woodruff key. I think the Commando's is a better arrangement, since the primary sprocket is keyed and is on a taper.



When the bike last ran, the flywheel came loose at a trackday and ruined the taper. Crankshafts are very hard to get for these bikes, so I had mine repaired, at considerable cost. I am now using an Electrex flywheel and alternator, 12 volt, 120 watt. This replaces the original 6 volt, 80 watt system, which was weak but which I never had any electrical problems with. http://www.electrexworld.co.uk/stk-163- ... 381-0.html

I raced the bike without a flywheel and had no problems, and it was nippier out of corners. Some people fit smaller, lighter flywheels for racing. I would want a flywheel for the road, though.

The original primary gears are helical, mainly to keep the noise down. A popular mod for racing was to change these for straight cut gears. This was supposed to be more efficient at transmitting power but is also supposed to be noisier. To be honest, I didn't notice the difference. A dry clutch would have been nice but the conversion was always, in my opinion, more expensive than it was worth.

 
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Nice pictures Dave,
A bit to keep me going "till the yellow bits arrive.
When the brass flywheel comes loose it sounds as if the engine is about to throw a leg out of bed.
I have found it's a good idea to lap the taper and the flywheel, finishing with joulers rouge, I've never had one come loose after lapping. My 450 doesn't get babied either.
Also check the cam for binding too. Set the opening clearence and roll through 360 degrees checking the clearence as it rotates. Best done with the springs out.
Desmo single cams are/ can be really bad. Imola cams are usually ok. My son's 500 Pantah wasn't too good and needed relieving, and they were supposed to be good.
Most close up and even have negative clearence, thus ruining the rocker follower or the cam face.
Usually it's the closing lobe that is at fault just where the flat section starts to curve. A diamond lap like Ezylap is good.
I changed the bear trap springs to made up 4kg springs that are the same shape as the twin springs, (1/2 the wieght of V twin) just to relieve some load on the bevels and Oldham coupling.
You'r right about parts being hard to get, and expensive. Especially compared to Norton bits.
Where did the straight cut gears come from? Old Race Spares?

graeme
 
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Graeme — those straight cut primary gears came from Ducati specialist, John Witt-Mann, who was based in Luton. I think I got the ones pictured in the late 80s, but the pinion ID was slightly oval. I noticed some slight fretting on the crank so I reverted to the helical gears until the opportunity came to replace them with a fresh set of straight cuts, but can't remember where I got them, since it was quite a few years back.

Steve Wynne* gave me a demo of how to set up the valve clearances to take into account the inaccuracy of the cams. I bought several 87 mm pistons from him and he made valves for me during the 90s. What really annoyed me about that flywheel was that I always lapped in the taper and checked it with engineer's blue, ever since I got the bike! I checked the Electrex flywheel too. I could not find a torque figure for the crank nut but it is now torqued to 80 lbs/sq in, so only time will tell if holds.

I always wondered about those hairpin valve springs (which I think were pinched from the 160 Monza?) being a bit too strong and maybe contributing to rocker shoe wear. Interesting mods you made.

[*For those not immersed in Ducati lore, Steve Wynne prepared Mike Hailwood's Ducatis when he rode the V twins in the late 70s]

The price of Ducati spares has been eye-watering for as long as I can remember. In this build, I have tried to keep the cost down as much as possible, which has meant a lot of workshop time, when I could spare it, over the last year or more.
 

xbacksideslider

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In my experience, there were two types of flywheel for the singles, the Energy Transfer magneto type and the Alternator type. As I recall, the ET type were brass while the alternator type were aluminum - at least in the narrow case engines.

The narrow case singles primary gear sets, in terms of alloys and hardnesses, were mismatched - they wore each other out, dumping their metal into the oil. That problem was cured with the wide case engines. Again, as I recall, the fix was to install a wide case gear set into the narrow case. On one engine I had a clutch basket's gears hard chromed but that wasn't so good for the rod's big end either - lots of oil changing until that cluth basket gear bed in to the pinion.
 
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John the later wide case engines from about '68 (they were wider at the rear mountings, and the sump was longer at the rear) had alloy alternator flywheels for the 250 and possibly the 350. The 450 had a brass flywheel and an alternator. The RT 450 had a magnito type flywheel.
The narrow case engine went as big as 350.
The primary gear and clutch are suposed to be a matched set.
The weakest link I've experienced is the gear box (transmission) 1st and 4th gears. The transmission has it's heritage back to the late 50's 175 engine.

The most interesting thing about old Italian singles is their ability to bend light. They can throw a dull yellow headlight beam that actually bends and falls on the road 10 feet in front of the bike.

graeme
 
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The painter delayed for two weeks and then made several mistakes. I had to take the parts from him yesterday so I could get some shakedown miles up before my self-imposed deadline of this coming Sunday.

You don't see the side panels because the painter got one of the stickers upside down and the other wasn't horizontal. Luckily he can get stickers made up locally and I can ride the bike without them.

I am happy with the front mudguard and seat, and the tank sides are grand but the long stripe down the centre of the tank is slightly on the piss. And he has yet to flat down the lacquer coat and do a final polish. I will try to get some more miles up tomorrow and then drive back - yet again - with all the yellow bits. The 450 sticker has yet to go on the seat.

Luckily, this is not for a show and I do not see myself as a restorer. I just want it to look nice and go well at the weekend and I will aim to finish it off over the next month or so, time permitting.

Taken with my camera phone, with apologies for the poor quality, but I was in a rush:



 
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I took the Ducati out tonight for its first spin on open public roads in decades. The motor felt strong, no smoke, no oil leaks, but a very heavy clutch action, which is definitely the new Venhill cable, and which I will deal with. The motor is well-behaved despite the big carb and race cam. Amazingly, the headlight actually works, thanks to the second hand QH lens I got from a scrap yard. The new Electrex alternator and rec/reg are doing what they are supposed to do.

More miles and more noise tomorrow. Then i need to check all the fasteners, check the steering head bearings, re-tension spokes, adjust the chain and drain the oil. I have several magnets in the engine to attract ferrous swarf, especially important with the new bore bedding itself in. For non Ducati people, the singles never had anything but a sludge trap in the crankshaft and a gauze filter to trap the really big bits. And that's it. The Commando lubrication system is positively advanced in comparison. The Ducati also has the further disadvantage that it is unit construction and the engine oil also lubricates the primary gears, clutch and gearbox.

I have an oil cooler/paper element filter and a modified spare timing cover that I will fit at some stage. In the meantime, frequent oil changes are necessary.

Edit: and check the valve clearances!
 
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Woohoo! Looks very nice! And best of all, another single back on the road!

Some things that worked for me,
Heavy clutch, try running the cable along the back bone of the frame and bring it out rear of the tank mounts, then let it lay as it wants to.
Try lapping the steel plates in the clutch with 900 wet and dry on a sheet of glass, this made a huge difference to mine.
The steels have burs on the edges where they have been stamped out, also the clutch basket fingers can get wear ridges from the plates, smoothing these will help the plates slide.

Wash in Locktite, ride and enjoy, re tension. (don't forget the right footpeg that holds the muffler)

(if the stickers are slightly on the piss that will make it more "original" )

Graeme
 
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GRM 450 said:
try running the cable along the back bone of the frame and bring it out rear of the tank mounts, then let it lay as it wants to.

(don't forget the right footpeg that holds the muffler)

(if the stickers are slightly on the piss that will make it more "original" )

Graeme
Thanks for the tips. I know the heavy action is the cable because I tested it with the cable straight, with the clutch perch mounted on an old handlebar. This Venhill stuff comes with a good reputation but it is very strange. I was playing around with the routing last night and the tighter the bend at the crankcase, the easier the pull. That goes against what I have learnt — that nice wide curves work better. I think the outer cable is too flexible. Each time the cable is pulled, it writhes like a snake. I made up a clutch cable for the Commando from a Venhill kit and it was the same. I ended up ordering one from Norvil, which was exactly the same length but was way better. The last cable I used was a modified genuine one from a 900SS and it worked fine, but the outer was a lot stiffer. I reckon I'll go to my scrap yard again and adapt something!

That bloody right footpeg and exhaust under the gearchange always annoyed the hell out of me!

How often do you check your valve clearances?

It's pissing with rain here now, and I'm not going to get it filthy before the weekend, so no riding today! Looking at your pics of the Moto Giro, I was thinking, Australia must be a great country for riding motorcycles (apart from what I hear of your predatory cops!). That and places like southern USA and the south of France!
 
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I bought Venhill throttle cables for the TT as the 40mm Dell'Ortos are the new type and very heavy, but they seemed to be no better. Funny that, they used to be excellent.

I would do a good check at 1000ks and then every 10 000ks. Depending on what / how I've been riding it. When it gets a prolonged hard time I will check them sooner.

In Brisbane, 5/8ths up the east coast winter is the best time to ride. It's not too hot and humid and it's usually fine. Good for leathers. Summer is hot and humid for 6 months.
The Moto Giro is on in August or September, perfect weather. (it'll probably piss down next year now that i've said that)
The cops are not nice, but if you go on a week day there's no issue. They are worse in Victoria, 1 k over and you're booked. So the cage drivers spend all their time watching their speedos and not us.
But it's probably the same everywhere, there's decent cops too.
 
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Thanks Paul. I have been preoccupied with the little Duke of late, so I must have a look at the latest on your Hybrid build.
 
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The Ducati will not be 100% ready for my self-imposed deadline of this weekend. I still have to design and fit a new exhaust system. In the short-term, I will have to make do with the old system, which I cleaned up as best I could. The paintwork still needs to be finish polished. I achieved a much lighter clutch pull by yanking out the nylon lining from the clutch cable. I discovered that the electronic rev counter is made for Harley twins and the like, and because this motor has half the pulses of the twin, the instrument under-reads. At least it fills the hole in the instrument pod! I will have to send the Falcon shocks back to England at some stage to reduce the compression damping, which is too severe for the road. I will get a new seat cover made, probably with a suede top and vinyl sides. And a few other minor cosmetic details need to be attended to.

I will post some more photos of the Ducati and anything else that catches my eye at the gig I will be bringing it to at the weekend.
 
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Hello Dave,
How's the yellow bits and the muffler going on your 450?
Any progress?
Or have you been too busy riding it?
graeme
 
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Hi Graeme — the paintwork is complete and on the bike. Yes, I have been riding it but more shakedown rides than proper spins. It's getting cold here now and I've got busy again, so I have fewer opportunities for riding. The painter seriously delayed me but he eventually got the stickers on properly and it looks presentable now. You have reminded me to take some pics and I will post them when I can! I can't reach the guy by phone who will fabricate the exhaust. I still have the old system on it, which is the main reason I hadn't taken more pics, since it remains an unfinished project.

I had to rebuild the Falcon shocks to alter the compression damping, which was much too severe, and I learnt a lot in the process. I also had to play around with the jetting and now it's pretty much sorted. I am surprised how comfortable and biddable the bike is, not having ridden it on the road since the early 80s! After a tickle, it starts first kick. Man, that Conti is noisy!

Dave
 
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