Hello folks,
I hope you're enjoying some good Spring weather for those of you in the Northern hemisphere.
Here in the UK April was unusually dry and warm and May is more of the same so far. Good riding weather for once.

Well, I've got the 750 TT1 replica running. It starts pretty well actually.
But I have a problem with the oil system.

The engine is a bit of a mongrel:
650 cases bored to accept 750 barrels (Monster I think)
650 crank but other internals mostly from a 350 donor engine
Gear set modified for dry clutch conversion
Cam oil feed is external via an Ipra cooler, but being 650 casings the oil return is through the barrels.
Each cam feed has a 1.3mm in line orifice.
Since the cam oil feed is upstream of the filter I installed what I thought to be a 35 micron filter in the common feed line downstream of the cooler. But on inspection it is just a 900 micron (0.9mm) coarse gauze.
Oil pump drive ratio is 22/44.

The first oil I used for a flushing run was 15/50. I filled the cooler before starting.
The oil foamed badly soon after starting until it filled the sight glass.
Visual check showed a good flow to the cams and no issue with drainage.
The engine probably ran for a total of 30 mins. I didn't run it through the gears
After draining there were no obvious hard particles in the oil but there was some magnetic sludge attached to the drain plug.
The cooler oil and in line filter were also clean.

After re-reading the notes that came with the Pistal pistons, I haves used 20/50 for the second run.
I have installed a temporary oil pressure gauge this time.
Again the the foaming occurs pretty quickly. The gauge shows > 10 bar (145 psi) on start up.
This seems high to me.
When cranking over on the starter, with the plugs removed, the gauge shows about 4.5 bar (65 psi).
So far I haven't let the engine warm up fully for fear of damage.

Also, to me, the crankcase breather seems to vent more air than I would have expected.

Some of my thoughts:
a) A blockage somewhere in the internal feed system causing high back pressure
b) Oil pump relief valve not working (I'm not sure what the setting is)
c) I didn't check the length of the 750 cylinder extension into crankcase. Could this be too long and cause the pistons to partially pressurize the crankcase?

Any other ideas would be greatly appreciated!
Thanks very much.
All the best
Rob

Foaming oil is one of those unending sagas on Ducati websites. Kinda like slipping wet clutches - even after 45 years of Ducati revisions to fix that problem. Here in Oregon i had the same problem/concerns this past winter, on several of my bikes that had had nothing changed from the year before. I was asking - what have i done wrong? And then the higher temps/lower humidity of spring got here. And the problem was gone! The same engines all look fine now when i start them. And, if you are not running the bike long enough to really heat it and “burn off” the condensation it will haunt you. Some say short run periods in winter are not good for engines.

Cheers,
MikeV

PS: maybe Cranky will have some better thoughts or suggestions on this.

Thanks Mike,
I try fully warming up the engine to start with.
I'm sure the neighbours will appreciate that
Cheers
Rob

I am truly hoping that Cranky will chime in on this; he seems to have some good knowledge of the oiling systems on these engines. I only commented because of my experience with several of my bikes this past winter, which concerned me, and caused me to search that topic online. We, in Oregon, now have similar weather to you, and the issue is gone. But there is some difference between seeing just air, or condensation (milky), in the site glass. I wonder if the inline oil filter, have not seen those in use, plays any part in this? MikeV

Thanks Mike,
I don't think the in-line filter is the issue.
It's very coarse so will cause very little pressure drop and the oil flow at the cams is not aerated at all.
To me it seems to be more likely either some kind of churning in the crankcase or maybe a partial blockage somewhere causing a large pressure drop and maybe some form of cavitation? The latter seems pretty unlikely I think, though, as I mentioned, the initial oil pressure does seem pretty high...
Anyway, I'll run the bike till fully warm on Monday, when the nearby non-retirees are away at work and report back.
Cheers
Rob

Ok I'm awake but not sure I can ad much to the discussion. Yes pressure seems high. Check and or change oil filter as it has an over pressure relief built in. Check system relief valve as well but that's not as easy to do. On fitting 750 barrels to to 650 cases check to see that the drain channels in the case mouth are properly ported. Most of the 650 cases are not but the 750 cases are. I seen this done on the production line at the factory with a porting tool.
-Cranky-

Thanks for the information Cranky.
The system relief valve is the separate type, between the crankcases.
Do you know what the setting is meant to be and if there's a procedure for checking this?
Really appreciate the help, even though it may need some very invasive investigation!
Cheers
Rob

Had some thoughts after I reread your original post and wondered what you meant " oil return is through the barrels". Checking some data your oil pressures are not that high cold. The 1.3 mm restrictors are a little big... recommend 1.2 Can you tell if its condensation from blowby or just air foam? Air would settle out pretty quickly. Wouldn't run a fresh engine that much if not under some load.
Just thoughts
-Cranky
Pics are comparison of 650 and 750 drain channel.

Glad you are thinking about this one Cranky. I have noticed this before, and used my dremel tool to smooth the pathways and match things better. If you were using drains from the rocker covers to the case somewhere it would not be as critical, but i still smoothed those grooves on the F1/TT1 900 engine. I did not block the drains off inside the heads, so i am down 1HP - drats.

I have wondered, once, what would happen if one of the several O rings on the clutch/oil pump side of the engine were left out? Would it result in lower oil pressure or aeration of the oil, or both? For a while this past winter i was thinking about checking that, but since the engines were running fine the year before (and built some time ago) it seemed senseless. Ah, the thoughts that haunt us.

MikeV

Ah the things that we think about > Another thought... the 650 cases normally don't have the metal blade back flow preventer under the oil filter. Shut the motor off and the oil cooler partially drains down. Start back up and you get some air in the oil but it bleeds quickly.