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Discussion Starter #1
Hi gang... I've a couple of questions if you will humor me. Towards the end of last riding season, I developed a small oil leak at the base of the vertical cylinder. As all of us seem to have a lot of spare time on our hands this spring I decided to tackle this myself. So, a couple of weeks ago, I stripped the bike down...
984283

The coolant has been drained, oil (Motul 300v) was just changed towards the end of last summer, and as a sump full of this shit costs an arm and leg, and is still clear in the sight glass, I've left it in. I've not touched the timing belt tensioner. My plan is to untorque the cylinder head nuts, let sit for an as of yet undetermined period of time, and then retorque and reassemble the bike.

My questions for the group are as follows:

  1. Has anyone ever successfully done this? I've researched this topic and read multiple accounts, and there doesn't seem to be any degree of consistency amongst the results. Sometimes it worked, sometimes it didn't.
  2. Does anyone see any problem with not loosening the timing belt tensioner prior to doing this? Keep in mind, I'm releasing the torque on the fasteners, not taking them off. The head should not come up more than 1mm.
  3. Has anyone had any luck, or know anybody who has purchased these knock off Head Nut Holder Wrench's? Ideally, I'd love to be able to rent or borrow one of these, but I don't know anyone around who owns a Desmoquattro who would have one.
984285

I guess that's it. As usual, your honesty is appreciated... If I'm deluding myself, by all means let me know.
 

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i'd say you're deluding yourself. if there's oil across the gasket loosening and retorquing isn't going to get rid of that - you'd need to lift the head and clean it all up and maybe give it a spray of copper. loosening for a while and retorquing seems totally pointless. i'd loosen and retorque them one at a time if you really want to (probably couldn't hurt), but leaving it loose is not something i would do. very rare for one to leak oil there, sure it's not a cam end cap o-ring or rocker cover gasket, or fuel tank weeping somewhere?
 

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Just curious, but can you identify the exact source of the leak, or do you see vague evidence of leaking in the general area? I don't know if you mentioned it, but did you thoroughly clean around the base? If oil leaks are anything like water leaks, they seek the lowest point but sometimes take odd routes getting there. I would agree with you it's likely the suspect gasket and maybe you'll get lucky by releasing the torque then retorquing. Perhaps over time and use, the cylinder head bolts unwound a tad. However, I would be inclined to follow Belter's advice. Good luck and please let us know the outcome and good luck to you.
 

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Hi gang... I've a couple of questions if you will humor me. Towards the end of last riding season, I developed a small oil leak at the base of the vertical cylinder. As all of us seem to have a lot of spare time on our hands this spring I decided to tackle this myself. So, a couple of weeks ago, I stripped the bike down...
View attachment 984283
The coolant has been drained, oil (Motul 300v) was just changed towards the end of last summer, and as a sump full of this shit costs an arm and leg, and is still clear in the sight glass, I've left it in. I've not touched the timing belt tensioner. My plan is to untorque the cylinder head nuts, let sit for an as of yet undetermined period of time, and then retorque and reassemble the bike.

My questions for the group are as follows:

  1. Has anyone ever successfully done this? I've researched this topic and read multiple accounts, and there doesn't seem to be any degree of consistency amongst the results. Sometimes it worked, sometimes it didn't.
  2. Does anyone see any problem with not loosening the timing belt tensioner prior to doing this? Keep in mind, I'm releasing the torque on the fasteners, not taking them off. The head should not come up more than 1mm.
  3. Has anyone had any luck, or know anybody who has purchased these knock off Head Nut Holder Wrench's? Ideally, I'd love to be able to rent or borrow one of these, but I don't know anyone around who owns a Desmoquattro who would have one.
View attachment 984285
I guess that's it. As usual, your honesty is appreciated... If I'm deluding myself, by all means let me know.
Proph my friend. You of all people know about shortcuts in engineering and wishful thinking don’t mix.
 

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Discussion Starter #8
Here are some shots I took of the leak last fall. Prior to taking these, the exterior of the vertical cylinder was cleaned thoroughly, and then the bike was started and left running until water temp was nominal.

I then inspected and took these:
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I could see no traces of oil leaking "down" to that point from the cam covers, although it is possible that the leak could have originated from behind the vertical belt inner cover (item 4 below) and was simply not visible.
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Very unusual to have a head gasket spring a leak like that. I would clean it all spotless and then spray the area with white spray foot powder (don't buy clear). then run it while watching and the location should show. If it is the head gasket order up a new one and plan on re-sealing the base gasket as well when you pull it apart.

Be sure to inspect carefully for any reason the gasket leaked (cracks etc) . any new vibrations?
A bad rod bearing or main might be allowing the piston to hit the head and push a leak. I have seen this when a tech set squish too tight by mistake. You might cut up a old filter and inspect the screen/magnet for metal. Look for copper in the filter and steel in the sump.

I don't picture your bike being a candidate for a main bearing but 748r have ti rods and they are prone to ovalize and spin bearings as low as 15,000 miles.

No panicking allowed until you are 100% that it is the head gasket unless you do notice metal or copper or feel there is a new vibration( thump thump) of the head and piston touching.
 

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The vertical head gasket on my 916 sprung a leak, but it was coolant that leaked not oil.

Can't see the point of loosening/retorqueing, if you're going to do anything then remove the head & cylinder to check for any faults and then replace the gaskets.

Don't know about the 748R but on the 916 vertical head there's an unused oil feed in the crankcase near the rear/right of the cylinder which is sealed with an 'O' ring (but that would leak lower down), to avoid any possibility of it leaking I plugged the hole by tapping it and loctiting in a grubscrew.
 

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The issue is, and this is a guess, that engine is total trash. You know I'll take it right off your hands.

Torque it. If it is somehow loose that may help. I had a leak like that, I may have mentioned it. I put to much bond on the base and it filled the oil galley about 3/4. There was enough oil in the head that the rockers should never flake ever again as they were swimming in Motul. (In my younger days I cared about oil)

Before I did the right thing and remove the head, i torqued the head nuts. It decreased the flow a good amount.
 

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Prophet,
I bought a 2001 748R a couple of years ago in boxes with a few parts missing. I know, what an idiot. Can you take a few photos around the bike with no body work on so I can check what is missing & what type of bolts go where please.
Cheers
 

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Discussion Starter #15
Prophet,
I bought a 2001 748R a couple of years ago in boxes with a few parts missing. I know, what an idiot. Can you take a few photos around the bike with no body work on so I can check what is missing & what type of bolts go where please.
Cheers
DM me... am happy to help however I can.
 

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Is the bike on a side stand? (gravity)
If it is I'd suggest looking closely at the cam O rings behind the belt pulleys, I would suspect them much more than a head gasket. I've only ever seen Ducati head gaskets weep coolant but i guess anything is possible, with that much oil though it should be very obvious where it's coming from.
 

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Discussion Starter #17 (Edited)
Is the bike on a side stand? (gravity)
If it is I'd suggest looking closely at the cam O rings behind the belt pulleys, I would suspect them much more than a head gasket. I've only ever seen Ducati head gaskets weep coolant but i guess anything is possible, with that much oil though it should be very obvious where it's coming from.
Well, well, well... upon closer inspection look at what I found...
985246

There is oil between the vertical belt inner cover and the camshaft bearing cap. I do ride in a rather spirited manner when I get her out, but not so spirited that oil could get UP here if it were leaking from the head cylinder gasket.

So this just got a lot more complicated. In looking at the exploded assembly views in the Spare Parts Catalog, it would appear to me that if the leak is coming from up here, it is in all likelihood coming from the O-Ring behind the timing side cap assembly... #8 in the image below:
985251

Does this sound about right? I've read the disassembly process in the workshop manual several times now, and it would appear that to address the replacement of the O-Ring is going to require, at a minimum, the following tools:

Degree Wheel Holder (88713.0123)
TDC Check Gauge (88765.1297)
Crankshaft Locking Tool (88713.2011)


The use of the Rocker Shaft Puller (88713.1994) is mentioned, but as I am not entirely disassembling the heads (I'm not am I?) themselves I don't see why this would be needed. Another step that appears to be unnecessary is the removal of the head itself, which would then require the use of Head Nuts Holder Wrench (88713.2096). Again, if I am off base here, let me know.

I've done countless engine rebuilds, porting work, etc. over the years, but it was all on 2 stroke RM and 4 stroke GS engines. Certainly never on anything which had heads that were anywhere near as complex as this Desmo. I therefore humbly defer to you guys with regards to where I go from here...

And I swear to god @Namor , if this goes south, I may take you up on your offer. ;)
 

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Yeah all the cam caps have a small o-ring that seats right at the base of the cover portion. It could be this, or the oil seal for the shaft behind the timing gear leaking as well. if it's the inner o-ring the front face of the cam cap should be dry. If it's the shaft seal then I would expect oil on the front face behind the gear.

I had some slight weeping from the out shaft seals on the motor in my cafe'd 748 that needed to be wiped down once a month. I replaced the cap with a clean used part because 'lazy' but it sorted the leak so far.

Edit: looked at your photo again and it look like traces of oil on the cam cover sealing edge but also on the back side? Tough call without being able to run a finger across it to see where the oil is.
 

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Well, well, well... upon closer inspection look at what I found...
View attachment 985246
There is oil between the vertical belt inner cover and the camshaft bearing cap. I do ride in a rather spirited manner when I get her out, but not so spirited that oil could get UP here if it were leaking from the head cylinder gasket.

So this just got a lot more complicated. In looking at the exploded assembly views in the Spare Parts Catalog, it would appear to me that if the leak is coming from up here, it is in all likelihood coming from the O-Ring behind the timing side cap assembly... #8 in the image below:
View attachment 985251
Does this sound about right? I've read the disassembly process in the workshop manual several times now, and it would appear that to address the replacement of the O-Ring is going to require, at a minimum, the following tools:

Degree Wheel Holder (88713.0123)
TDC Check Gauge (88765.1297)
Crankshaft Locking Tool (88713.2011)


The use of the Rocker Shaft Puller (88713.1994) is mentioned, but as I am not entirely disassembling the heads (I'm not am I?) themselves I don't see why this would be needed. Another step that appears to be unnecessary is the removal of the head itself, which would then require the use of Head Nuts Holder Wrench (88713.2096). Again, if I am off base here, let me know.

I've done countless engine rebuilds, porting work, etc. over the years, but it was all on 2 stroke RM and 4 stroke GS engines. Certainly never on anything which had heads that were anywhere near as complex as this Desmo. I therefore humbly defer to you guys with regards to where I go from here...

And I swear to god @Namor , if this goes south, I may take you up on your offer. ;)

The cams have come out to replace the O rings on either end so that means set it up like you would for a belt change or valve clearance check and remove/refit. Easy if you take your time. I would do all the O rings and gaskets while i'm at it and of course, check the clearances while you're in there, new belts too, check your tensioner and idler bearings etc while you have it apart.
If you're not confident to do it yourself the cost by your tech would be the same as a clearance check and shim for the labour as it's basically the same job with a few extra parts.
 

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i replace those o-rings at every valve clearance check. they can weep, and i'm guessing lots of people never replace them, given how flat i usually see them. they're less than a dollar each. 88640011a.

you need the rocker pin tool to slide the opening rocker pins across (not all the way out) to get the cams out to change the o-rings. it's pretty easy.
 
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