Psyching myself up for the top end - any veteran eyes up to read borescope pictures?

[lizzywhite45]

It actually runs fine and has given me about 4,200 miles of service in the last year - it just leaks. A little bit after my last post, I did conclusively figure out that the oil I was seeing was from some sneaky valve cover leaks, not bad gaskets. Not that that means the gaskets are good to go! They're just not leaking, seeping, or wicking *yet*.

I rebuilt the carbs about a year ago, and the boots are still supple. It was definitely running pig-rich on idle for a while - I had the idle mixture screws so rich I could smell it at longer stops, but didn't get around to leaning it down for a while. The fact that it's in 1 and 4 way more than 2 and 3 makes me think I need to properly sync them again. I also had a long storied saga with a flabby ignition system that finally died, so I wonder if some of that carbon is from bad timing and/or weak spark for a while.

The valve stems are definitely hardened up. Or, at least, I'd be shocked if they weren't, given the nature of its morning smoking habit.

Do you think the average machine shop will understand what I mean if I ask them to fly cut the head and block? *I* know what you mean, but I am not confident enough in my mechanical knowledge to say whether they will. If not, what are some key words or descriptions I could give them over the phone so I know we're speaking the same language?

I already snagged a couple key items (the head gasket in particular) a few months ago, and this time I've ordered all the parts I think I'll need.

I did decide to get a good quality used cylinder head and build it on the bench, versus attempting to rebuild and rethread my current head all at once. Comparing about $120 shipped and several hours of work just for the rethreading vs. $175 shipped for a head that I *think* is in ready-to-rebuild condition made me see the latter as the better move. This way, I'll have one freshly-rebuilt head and one reserve head to play around with or call upon in case of disaster, versus one head that I'll be crossing myself over every time I bolt or unbolt something. Also, I can take my time to do the bulk of the work properly and slowwwwwly instead of under pressure as my engine sits open-topped and vulnerable.

Hey, sounds like you’ve got a solid grip on what’s going on. Good call figuring out the valve cover leaks, those can definitely mimic base/head gasket issues.

If you're pulling the top end, I'd go ahead and hone all four cylinders, re-ring, replace valve stem seals, and lap the valves. Doing just 1 and 4 might save time now but could bite you later.

For the machine shop, ask if they can "resurface the head and cylinder block for proper sealing." Most shops will know what you mean by fly cutting, but using the word "resurface" clears up any confusion.

Smart move buying a second head to build on the bench. That gives you time to do it right without the pressure of having your motor open and vulnerable.

Keep us posted, you're definitely heading in the right direction. These old GS engines reward a thorough job.