Good point on the spalling and early issues. This visual spall check is still mentioned into the later SM, so I checked mine. I had none on my cam tips and tops of buckets nice and smooth. So, ok, I can buy the early Revolution cam problem statement then. It would seem it was a known issue when they wrote the damn book and had you look for it. Late model cams have lateral markings to improve oiling as well which might help eliminate spalling. To the untrained eye, the 1250 cam lobes look fkd at first glance but it's part of the design. I've seen pics of them a long time ago, so I was prepared.I heard it was spalling of the tappet / shim bucket face and cam lobe surface - apparently bad heat treatment of one or the other - when I bought new H-D tappets for my new engine build I made sure there were no old dated tappets in there - if that problem existed in this thread engine there would be evidence of spalling of the face of the tappet and cam lobes, that could cause binding of the tappet in the bore and cause valves to get stuck down and hit the piston as it rises - that would do it and there is metal seen in Rons point out photo we'd have to see the cam and a close up of the tappets to say much more - I'd think the owner would have noticed that if so ? Just another example of don't ever buy the first couple years of anything as generally the problems get worked out in later model years.
Most cams for buckets or flat tappets have a taper on the tips to promote rotation often with a radius on the part the cam lobe tip contacts as in the lifter faces. My cams have this taper but I didn't bother to measure how much. Generally in the .001-.0015 range from other engines I've checked. Visually it can be seen as the one side of the lobe tip is shinier then the rest of it, as well as evidence of circles on the buckets also indicating rotation. Not sure if that slippery valve shim can rotate the valve or not as it looked more like they were spinning on the valve tip instead. . Looked fine so I move onto the shimming task.Yea, also some cams have a very low % ramp on the face of the lobe to help promote spinning of the tappet/follower - if they don't spin a little the cam lobe tip can wear a trench in the face of the tappet and just wear into it until failure occurs, especially if the material was softer than desired. The stock valves are rotators as well to help spread out wear around the stem and help keep the seat and valve wear even. My new AV&V Canada high flow valves are said to be non rotators due to the unique locks on the stem but they claim the entire spring and valve will slowly rotate as an assembly so no worries - you can imagine the forces on the cam chains at 9000 Rpm as the valves open and close and pass that cam fwd & back twist on to the chains. Probably why Ducati went with the Desmodromic spring free system to pick up a nice hp boost for free - better valve control but yes, a bitch to setup and adjust -
Yup, buckets beat to crap from the cam cap being jammed from the cam lobe. One thing that stands out is those are not standard valve cover gaskets as in non OEM if those are what I'm looking at? Somebody has been in there before. There is evidence of the caps being loose for a while, which might have eventually caused the bolts to snap. Note the fretting area where the cap contacts the head. When you took it apart, where the exhaust cam caps tight, or loose as well? As for possible bent valves and broken chain, these are secondary events. Neither was the cause of the cap bolt failures, as I see it. Bolts, cap into the lobe, into bucket possibly extending valve lift to allow piston to hit them. Chain looks like repeated shock loads, elongating the holes. At some point it just plain had enough. Head is dinked anyway so what I'd do is compress the buckets below the top surface of the hole and dremel out the crushed aluminum at the top so the buckets will come out and then remove the valves to see if they are actually bent.Hope these pics help.
Those cam lobes don't look too bad actually, considering. No obvious spalling. Can't tell if they are stock or not. The stock cams should have compression releases on the exhaust cams if stock. I still feel the valves are held slightly open from the buckets not being allowed to extend fully from the top of the hole pounded in. Only way to know for sure is get the buckets out and see if the valve pops back in.Looks to me like buckets and valves got stuck down by debris created by the early '02 Revo tappet/cam wear problem - may have been aggravated by the earlier disassembly debris and/or improper cam cap torque but that engine ran for a long time to wear those tappets that bad - old damage, creating debris along the way. Once buckets get jammed down and valves hits piston repeatedly the cam vs piston fight began and the cam cap lost due to weak bolts ( and they may have been loose for some time look at the end wear on the cam cap - one may have broke first that broke the cam cap itself and it was all downhill from there, cam lifting up to get away from stuck bent valves -