I love digging into a used bike. You find such interesting things. Tearing down in prep for eventually getting the 351 going. Checked valves, even though I intend to get new valves and have the valve seats done. When I pulled the cams to get the head and cylinder off, I found some interesting damage on the valve buckets. What do you think, sitting too long with some moisture in the head? Bike is a 2009 with 8660 on the mileage, but I know it was not ridden for a couple of years. Cam lobes and journals look good, although one exhaust lobe has a very slight streak of color. BTW, the two buckets without the corrosion were both at the bottom limit of clearance.

 

The PO also installed a Krieger, and it seemed fairly tight. Any chance that contributed? Suppose I should also check the chain stretch while I'm here.

 

Now I see the threads popping up where people have noticed this before. Wonder if it is more of a metallurgy problem, and I wonder how common it really is at this mileage point?

 

What do you mean by 'bottom' of their clearance? Tight or loose? .... then answer the question, are you a fracker?
I have never seen anything like that, but it looks something was going on there. I'd take another very close look at the cam lobs. That is not corrosion, if it was it would be everywhere. My guess off the hip would be those valves were way too loose and impact with the cam lob caused or way too tight and heat/friction caused metal failure..
You never know the mechanical abilities of the OOwner. I can't imagine a world where a tight cam chain would do that.

 

Sorry, "bottom" as in, lower limit, too tight. One intake and one exhaust. The others were in the middle of the range. Fracker? I must be missing something.

 

Should not be caused by the tensioner, but it couldn't hurt to check adjustment when you put it back together. Here's a link to my google doc instructions. I can send a hard copy if you send your address to me by PM or email. Hope that helps in your rebuild.

I would guess the bike may have not been run long enough at one point and some condensation occurred, which would cause corrosion. The reason to run a bike long enough to get fully up to operating temperature when running it. The problem can be caused by starting a bike for short periods like in the winter. Better to run to full operating temps then park it. I tend to do what people don't like, leave the petcock on so there is always some gas in the float bowl, draining it before starting in the spring. If the float is working right there will be no problem. In around 30 years of doing this I've never had a problem. The only time I had a problem was when I turned the petcock off on my 650 then let it sit through the winter. The float needle seized in the carb allowing the gas to overflow when opened on that first spring day. Gas ran out, fortunately the intakes were closed and I didn't spin the engine over. Took the carb apart and cleaned up the needle and the area where it went in the carb. No problem after that, but I never turned off the gas and drained the carb again. I put in some Stabil and let it sit. If it stuck after that it would be quite obvious, but it never did. This is how I dealt with winter. Others may feel it isn't right, but that's my choice.

 

Whelp, this isn't going well. Sat down with Bill Blue yesterday and looked over my head when I dropped off they cylinder core. I was wrong. The cams are damaged. Those lobes corresponding to the most damaged buckets, although not pitted or discolored, are worn to a fairly sharp point, both intake and especially the exhaust. It appears the valves got really tight, or there was some oil contamination.

At any rate, I'm concerned now that the cam journals may be excessively worn (some light scuffing visible on the cap-side journals), and with that much material worn off and floating around in the oil, I have to wonder what kind of shape the crank bearings are in.

Minimum, I'm looking at new cams. If the cam journals are too worn, a new head. And that's before the bottom end examination. Kinda regret starting down the big bore path and finding it, but I'm not sure how much longer the engine would have lasted.

 

Start shopping for a complete engine? Maybe easier, or ......time for a NEW BIKE!!!!

 

I hear ya. Hate it when that happens......
But was mentioned above, it is sometimes cheaper to start over with a new engine.