I just finished a top end rebuild on my '77 w/35,000 miles due to oil leaks, and I bought an Athena complete gasket kit ($65 on Amazon) due to many OEM gaskets being NLA. So just FYI, here's a review on the gaskets and what I found wrong in the top end.
First, the Athena kit. I used only the gaskets and O rings relative to the top end, so can't opine on the bottom end parts. The base gasket had one hole slightly off center - one of the ones that goes around a 12 mm O ring at the rear. I trimmed it enough so the hole cleared the entire O ring. The valve cover gasket had one portion so badly mis-shaped that one hole was off by almost 1/4". No massaging possible, so the gasket was unusable. I used an OEM gasket there. The head gasket looked perfect. All O rings and the knock pin seals were excellent. This kit uses knock pin seals that are slightly longer than OEM and are deeply chamfered on the ends. They squish flat when the head is torqued, providing a positive seal. Valve guide seals - green. Not sure what material they are, but they fit perfectly and grab the valve stems well.
Stuff that was toast.
The cam chain rollers were both hard as rocks and had the imprint of the chain links embedded in them with small chunks missing. So they looked more like damaged sprockets than rollers. The valve guide seals were also brittle and broke like pretzels when I tried to remove them. Same with the O rings and knock pin seals. The cam chain tensioner blade had some small chunks missing. Other than the valve guide and knock pin seals, I replaced all of this stuff with new OEM.
Carb intake boots - these are getting to be a serious issue for us. The originals were hard, brittle, and cracked. I'd accumulated some over the past from ebay, cmsnl, David Silver, etc., but #2 and #4 were all I could find. So I flipped over a 2 to use as a 3 and used a spare #4 as a #1. Getting all 4 carbs fully seated was very difficult, but it worked out perfectly.
Piston ring gaps were at the max, so new rings went in following a light job with a 240-grit ball hone. Bores were at standard measurement w/no detectable out-of-round or taper. I removed the carbon ridge before honing. All valve seats and faces had light pitting which I lapped out...all except three exhaust valves which were so badly pitted, I had to replace them - with good used parts. BTW, I did a compression and leak down test before tearing it apart. #3 compression was around 20 lbs below the others, and leak test showed #3 exhaust valve leaking. Odd that the bike ran so well. Anyhow, I fired it up last night, warmed it up, synched the carbs. It's smoooth and quiet!
