Like a dummy I didn't pay attention to the orientation of the woodruff key when I replaced the vertical exhaust camshaft. Does anyone know if the key is oriented in delayed or advance position for a 2002 748s? For reference here is an image from the workshop manual:
I would have thought that from the factory it would have a straight key and that any offset would have been done during tuning? If so then you need to know if it was advanced or retarded so, unless whoever tuned it can be contacted and can remember what they did then the best way would be to check the timing to see what it actually needs.
Your post suggests everything is back together but if not, the safe option is to refit the key in the advanced position (on the exhaust camshaft), as this will maximise your valve to piston clearance. The reverse is true for the inlet camshaft (retarded). If the bike runs badly you have your answer.. Personally I'd fit plain woodruff keys and adjustable cam pulleys. You'll need to set them up with a degree disc and dial gauge but after doing so you'll be all set for fine tuning, if necessary.
Thanks guys. After talking to a few very knowledgable Ducati owners, I learned that on the Testa Bassa heads, the vertical exhaust is supposed to be retarded so I guess I will go with that!
All you can really say is that an advanced inlet and retarded exhaust would equate to maximum valve overlap. Similarly if the inlet was retarded and the exhaust advanced this would equate to minimum valve overlap. As a very general rule of thumb; maximum valve overlap better suits high rpm riding and minimum valve overlap better suits low rpm and mid range. Think of the 11° Testastretta, which is very much a road bike engine. It all depends on what type of riding you do and to what extent the bike is modified. There are a lot of variables to potentially factor in..
Thank you so much for this informative post. I bought the bike used recently so I dont know too much about its history. The bike came with a 50mm Leo Vince slipon and 45/50 midpipe. To be honest, I just want to put it back together like it came from the factory. I dont intend to track this bike, nor do I ride like a lunatic on the roads. The folks I talked to believe from the factory, the offset key was set to retard position in order to account for the Testa Bassa head, however nowhere is this documented. Even in the parts manual, the key specified does not have an offset, though the ones for all the camshafts have offsets, though it does not say if the key is used to advance or retard the cam timing.
You're welcome sir! Most of the time I'm not sure if my comments are useful or not so that's nice to hear. This is a difficult one. A couple of questions: - Do you know what position the inlet key is in? - Are there any markings on the key(s)? I downloaded a workshop manual but it doesn't appear to be the same as yours. That could lead to confusion! In my copy the markings on the keys relate to degrees of advance and retard.
My parts manual for a 2002 748S specifies part #74172.1008 for the vertical exhaust which I believe does not have any offset. The key I have has an "H" on it which according my workshop manual is 16 degrees (part #680 1003 1H). Interestingly, in my parts manual, this part # is specified for the inlet cams, though it doesnt say if the orientation is advance or retard. The horizontal exhaust cam specifies part # 680.1.007.1A which is 6 degrees. Unfortunately, when I took apart the camshaft assembly I didnt pay attention to how the key was oriented so I dont now if it should be in advance or retard position.
I'm glad I mentioned the manual as the copy I have only goes up to 'E', which is listed as 10°. My feeling is to place it in the advanced position. If out, at least it's safe in terms of valve to piston clearance, whereas if you place it in the retarded position and it's incorrect, you'll be 32° out, which is a fair bit. The other option is to buy a plain key and then you're sitting right in the middle. Perhaps that's the best or least worst of both options? Ideally whatever you decide you'll still need to check the valve timing. If you decide on the retarded position, I'd advise turning the engine over by hand before attempting to start it. Obviously it's your call and I understand what you've been advised and I'm probably being over cautious but I don't think there's any way of being definitive here.
Thank you. I will take your advice to manually crank the engine to make sure the valves do not hit the piston. I think what I really need to do is man up, buy some adjustable pulleys, a timing wheel, gauges, and learn how to degree cams myself!
No problem at all. Yes indeed! Adjustable pulleys do seem the way to go. That said I'd be interested to see what happened if valve overlap was reduced, particularly on the exhaust. Just my take but 'tuning' bikes always seems to be about increasing performance; more power etc and I'm not convinced that always makes for a good road bike. On that subject and after thinking some more and based on a few assumptions: - The bike most likely left the factory with plain woodruff keys (already mentioned by Dukedesmo). - Any work on 'dialling' the cams would have most likely been done to increase valve overlap, not reduce it. It remains an unknown but 16° advanced is a lot and seems unlikely, whereas 16° retarded is still not as much as the 748 SPS, if you base this on the standard settings for each bike. Good luck and nice to hear back when the bike is all up and running.
I am not so sure about this. Everyone I have talked to says retard on the 2002 748s Testa Bassa head was standard from the factory. Of course there is no documentation anywhere to support this. I see that there is a vertical exhaust camshaft supposedly from my same year bike on ebay which I am tempted to buy just to see the orientation of the key.
I'd spend my money on a degree disc and a dial gauge (ideally two). It's the only way to get a definite answer. Based on the specifications in the manual I downloaded, you should get around 18° at 1mm lift but if you get around 34° then it's been adjusted. It seems odd that Ducati would have used such a large offset to achieve standard valve timing. Why not just machine the cam lobes correctly in the first place? Perhaps they had a job lot to use up and this was their solution.
