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Hi,

I used to have a description of the origin of the top end lubrication problem in the parallel twins, plus a modification that fixed it. But having looked in all the normal places that I normally keep this kinda stuff, I can't now find it ...

(I'm fairly sure that it came off the Pantaheads list on Micapeak. But having tried to re-subscribe to that and not got a reply, I'm wondering whether it's still active. Anyone know ?)

Anyways, if you do have any knowledge of this particular problem and its fix, I'd be grateful if you could post something here.

TIA.

Craig

Ok, I'm replying to my own post which seems kinda unnatural; but ...

Den off the Micapeak list sent me this:

The problem stems from the aluminum discs that are used inside the geared end of the cams. They are used to prevent the oil from merely passing straight through the cams. Those caps are a press/interference fit, but they are pretty thin and soft. With the constant heating/cooling cycles the discs can loosen. I read where a fix would be to use a large INTERNAL SNAP RING up inside the cam against the cap. Surely the spring tension of the snap ring against the inner wall of the cam would be enough to keep the cap secure even without going to the trouble of machining a groove for the snap ring.

And, sure enuf, the guy who's recently got one of these engines just sent me this:

"This was probably what did for the red one that I have, in that both plugs were missing when we looked inside the motor."

Yes Craig this is the problem, you only have to fix a better plug solution there and viola end of problem.

Well having had a look at a later engine that came as aprt of the deal, it would appear that Ducati gave some though to the probles of these core plugs. The later engine has some form of serated washer to hold the plugs in.

We are looking at a pressed in plug with an extension on it, so that they will join within the camshaft sprocket and there fore not be able to move.

Engine re-assembly starts in 10 days, rolling chassis will be done on Sunday. Aim is to have it fully up and running over the Christmas bread.

Hi Steve & Chris,

(Ok, I know this is getting a bit a**l 'cos hardly anyone cares too much about the Parallel Twins; but ....)

There's some stuff on this in one of the Mototrans books I have. In brief, one fix was to fit an oil cooler which also directly fed the head.



The other fix, as suggested by Ing. Taglioni was, naturally (!), to fit Desmodromic heads (the assertion being that much of the valve gear problem could be traced back to too strong valve springs and a too small cam chain.) I think it was also Fabio who came up with the oil cooler idea, btw.

Ciao,

Craig

i thinking about a parra twin for my girlfriend but reading a few horror stories ,maybe i'll think about a single-although kick starting may be a problem for her

nottonight68 wrote:i thinking about a parra twin for my girlfriend but reading a few horror stories ,maybe i'll think about a single-although kick starting may be a problem for her

Why not a Pantah? Small, light, reliable, available, electric start, arguably Ing. Taglioni's greatest design ...

Ciao

Craig

how high is the pantah seat ?

nottonight68 wrote:how high is the pantah seat ?

760 mm, according to the 500SL workshop manual on Steve's site ...

Craig in UK wrote:Hi Steve & Chris,

(Ok, I know this is getting a bit a**l 'cos hardly anyone cares too much about the Parallel Twins; but ....)

There's some stuff on this in one of the Mototrans books I have. In brief, one fix was to fit an oil cooler which also directly fed the head.



The other fix, as suggested by Ing. Taglioni was, naturally (!), to fit Desmodromic heads (the assertion being that much of the valve gear problem could be traced back to too strong valve springs and a too small cam chain.) I think it was also Fabio who came up with the oil cooler idea, btw.

Ciao,

Craig

I actually have one of these engines with the oil cooler fitted, we think that it is an 81 GTV. Whilst it is Desmo in no way does it cure the problem!

What they did was take a bleed off under the oil pressure switch and feed the oil to the head via a cooler. To do this they had to block off the normal supply up through the block. What this does is give a supply controlled by a 2.5mm hole to teh cams and allows the oil to drain back down at a standstill. The cams still have the aluminium washer in them, though helped by some sort of spring washer.

To cure this on both engines what we have done is clean up the inside of the cams, where they go in the sprocket and put aluminium plugs in there held in with locktite. This way they press against each other and cant come out, end of problem.

What they should have done is put a grove for a circlip in before they hardedend the camshafts, much cheaper and no possible problem.

Recently I had occasion to drop the motor of my 500 Sport Desmo. This gave me the chance to install a couple of 1in. internal snap rings into the gear end of each cam to hold those aluminum caps in:

Den wrote:Recently I had occasion to drop the motor of my 500 Sport Desmo. This gave me the chance to install a couple of 1in. internal snap rings into the gear end of each cam to hold those aluminum caps in:

Hi there, very new to this list, about 5 mins in fact:-), I'll do the introduction in my next post, but just wondering if this is the definitive fix for the oil cooling problem, or is there another way that did the job better even though it may require more work to do??

Actually there wasn't an oil-cooling problem, but the headgasket kept leaking oil. When that got out of hand, the camshafts got starved of oil, destroying head (camshafts run it without bearings) cams and rockers.
Fitting an oil-cooler is just a bonus when doing the plumbing outside the engine.
You could press an alu piece into one camshaft, and turn it down a bit and fit an o-ring to seal the other.
Don't forget to fit the shims on the camshafts so they don't move sideways too much.
cu
ducadini

ok thanks, I will be doing total strip engine down and investigate all. A bit back there was an article on them in one of the mags with pictorial instructions on how to remedy all the factory faults, have to see if I can search that out.

http://www.paralleltwins.com/accueil.html

If You're into french, this site might help sometimes

cu
ducadini