I have just returned from a 2 hour trip on the 748 and noticed oil all over the back of theengine/gearbox, it looks like it is coming from the crank cases breather, isthis normal for a duke??? If so is there anything I can do to rectify it. I’m guessingthe system may be blocked.
No, it certainly isnt normal...it suggests the crankcases are being pressurised, and that to me says rings at the very least...if not a piston failing. Have you noticed smoke at all ? Normally such an occurrence would be in combination with lots of smoke pouring out of the pipes, or oil in the airbox...so have alook at that too...It MAY be something simple...like a split breather hose..but PLEASE carry out a thorough inspection before riding again. You may just have over filled the engine with oil......
Perfect response from nog, a split in the hose would be my first check as I think you would have mentioned if it was smoking a lot. Steve
Firstly is it overfilled with oil? If so that could be you problem. The breather is plastic and bonded together, is the integrity of this joint still intact? You are always going to get some pressure there as those pistons when the tavel down the bore have to move air.
I haven’t over filled it with oil. It does smoke very lightly when it’s cold and ticking over but I would say that it looks more like condensation than oil burning. Neither I nor my mates have noticed any smoke when its being ridden. I’ve just done a bit of research and found an article that was talking about the reed valves in the breather system and how they can get blocked with oil at high rpms and therefore can’t drain the oil back into the crank cases fast enough resulting in oil over the back of the engine. http://www.ducati-upnorth.com/tech/breather.php Considering that I have just been out for 2 hours ridding it hard trying to keep up with a mate who is on a zxr10 I thought this could soundplausible? I’ll havea look for a spilt pipe and oil in the airbox tomorrow.
Hopefully its a split link pipe on crankcase breather as covered above in detail. I'm guessing it is a stock breather set-up. Either way it wouldn't hurt to carry out a compression check on both cylinders if you have access to a tester.
Yes it’s a stock breather set up. I’ll grab the compression tester from work tomorrow and test them, what psi should they be??
there are always exceptions and depends on state of battery/open or shut throttle etc but around 150 p.s.i. upwards is what your hoping for and it's important that they are about the same reading - within 10 p.s.i.-ish.
Front cylinder isn't too bad but you still need just the right socket extension so that you can clear rad when you attach adjustable wrench. Ideally your deep reach socket will have a rubber sleeve to grip plug as it makes life easier. It's an M12 threaded plug but hex head can be 16 or 18 mm across flats (NGK is usually 18). You will see factory recommend Champion but most of us use NGK equivalent. Rear cylinder requires more attention though (hopefully you will have quick-release fuel connectors but standard ones still need releasing/attaching very carefully and it's worth getting some spare 'O' rings as they only cost pennies) or you can carefully maneauvre/swivel tank just enough out the way to get access to plug but it's a real balancing act if you are going to take a compression reading rather than plug changing, so better to either remove tank completely or get someone to steady the tank while you use comp tester. I always get a towel ready to slip between tank and plenum chamber fairing to prevent paint damage (if not removing tank completely).
It may not be all that bad.... These motors can pump quite hard. Is the breather the early type? alloy casing rather than all plastic? These are quite prone to leaking around the threaded base where it screws into the engine case. The alloy casing is "crimped" around the top and bottom and can leak quite a bit as the crimp loosens as well. As mentioned already, could be a split pipe. It's usually the short connection between the vent and the separator tank. Last thing to check is emulsion build up in the pipes and/or tank, blocking the breather system. If you're getting excessive case pressure, then it usually pushes oil up into the airbox. Lift the tank and check the recess where the breather pipe entrers the airbox. Depending on when it was last cleaned out, there could be a little and nothing to really worry over. If there's a lot then maybe there's other issues.
I couldn’t do the compression test today as my tester only goes down to m14 but I had another look at the smoke on tick over and I’m convinced that it is just condensation as it looks white and you can see the droplets forming in the tail pipes, this clears after a few minutes of running. I also took the crank case vent pipe out, I could not see any signs of a split or cracks but I found that the top hose clip was loose so I replaced that with a jubilee clip. I’m pretty sure that the oil is coming from this loose clip and/or the holes or thread in the very base where it screws in to the engine case (as suggested by nelly) as I can see fresh oil in the small holes. When I took the tank off I checked for signs of oil deposits but the air box is spotless apart from a very small amount of residue on the underside of the tank. But I’m guessing that as the tank is yellow any amount of oil/ dust will show up easily.
I think you've pretty much cracked it tbh. That's pretty normal looking and a new jubilee clip and a reseal of the breather into the cases cures it. Just an aside, have you tightened the lower clip since you took the photo :wink:
Good news then. Just out of interest, your top breather picture shows what looks to be a split just below the top jubilee clip but it must be a thread of rubber or something instead?
Nelly: the photo was taken just before I tightened everythingup. I never resealed the breather into the crank case as I could not move itand did not want to damage anything, I’ll try it like that and if it needsdoing I’ll take it apart again, does it just unscrew or pull out of the crankcase? Chris I see what you mean about the picture but It’s not asplit, it must just be oil or some sort of mark because everything was wipedclean and checked.
I managed to do a compression test today, front cylinder wasreading 137 psi and the rear was 140 psi. Not quite a 150 but it’s nice to knowit’s not too bad.
that's fine Jay - you're in the 'ballpark' Even if you did a fresh test with a second battery connected it could rise by around 5 - 10 p.s.i. i'm guessing test was done with throttle open?
