Interesting that your left hand piston has seize marks at the side as well as back/front. There should be more clearance at the side of the piston, whereas the back / front skirts will be in more intimate contact with the liner.
Jensen / Ed are good judges of what the root cause might be but I would definitely want to replace the pistons after that much trauma. If you decide to do that, getting the barrels re-bored to match oversized pistons is a minor expense that will give you peace of mind if nothing else.
As you have already suggested, you should check all oil ways and take a look at the oil pump and filter.
Seizure is a 'chicken and egg' situation with too much heat - too little oil escalating each other until you get the result you have here.
G
What a concept - A Girl Bringing Back Her 1966 Super Hawk
First I see this engine as having Lots of Miles. (running time)
I think the LS wasn't timed correctly and it ran extremely HOT. It should have new pistons installed if the bore is in spec (I doubt they are) and if not a bore job and new pistons and rings and possibly new pins. The cam chain tensioner is shot also. The pics show me it had very dirty oil so all parts will need looking at for sure. Suspect parts would be the 14mm brass bushing, kick starter shaft, kick starter pawl and all gears. .........................lm
Okay, great, thank you, fellas.
Lots of Miles, yes - 18000 plus. And it was ridden daily and hard, but it was maintained (or so I thought). New pistons/rings, hone/bore, cam chain tensioner (I've already ordered the bottom cam chain roller). Which bushing, LM? The kickstarter pieces are relatively new, as is that side case. It broke and was replaced not too long before the bike died. That doesn't mean I won't inspect it carefully. The oil looks dirtier in the photos than it is in person. It has been sitting in the cases for 40 years, as well. I was very religious about oil changes - every 1000 miles - as well as keeping the filter cleaned out. But - things are what they are! Hot - yes, I agree. I really appreciate the input, please keep it coming. 1965 CB77 305 Super Hawk
1989 NT650 Hawk GT 1981 Yamaha XJ550 Seca
I've been perusing cam chain tensioners. I see there are two different ones - the early one 14500-268-010 is apparently what I have - it has the shorter casting for the tensioner pin, whereas the later one (-020) has a longer casting and apparently a longer pin on the tensioner. Am I correct, and are they interchangeable? My engine number is 1027601, which falls into the range for the -010 tensioner....
Last edited by sarals on Mon Jul 09, 2012 3:27 pm, edited 2 times in total.
1965 CB77 305 Super Hawk
1989 NT650 Hawk GT 1981 Yamaha XJ550 Seca
By the way, I took the frame outside yesterday afternoon to inspect it in good light (my old glasses shod eyes...), and gave it a washing off, as well. Good news. The wiring harness is excellent, as is much of the paint (although it will get repainted). The rear fender is really good, but the front fender needs help (I know a fabricator, and I'm going to ask him if he can add about 8" to the fender).
This was good to see after the mess the engine is in... 
Last edited by sarals on Sat Nov 08, 2014 7:27 pm, edited 3 times in total.
1965 CB77 305 Super Hawk
1989 NT650 Hawk GT 1981 Yamaha XJ550 Seca
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