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**seinwave** · 08-26-2025, 10:33 PM

Cylinder 1 - the major suspect.
I see a lot of burnt oil (the shiny stuff on the bottom lip and piston head, right?)

a LOT of burnt oil - but it seems there's a little bit on the piston head (from the rings) and a lot under the intake valve (bottom of these sets of image) - or is it the other way around, and the valve leaks on the head while the rings lean around the edge?

I also think I see some ridging (damage around the radial direction) and possibly scoring (damage up and down the cylinder) in this image (right hand side). It's hard to tell because the crosshatch lines catch the light differently at slightly different angles - but there seem to be a lot more lines going straight around the cylinder here than on other cylinders.

Cylinder 2 - looking good enough, I think
Cylinders 2 and 3 have cylinder walls that look a lot like this. This seems to be pretty clear cross-hatching to me, which is a good sign. EDIT: now I'm seeing a horizontal line in this image...

However, you can still see there's some burnt oil. Old rings, or about what you'd expect from a 44 year old engine?

Cylinder 3 - even cleaner
Cylinder 3 has the same pattern as in 2 on the walls. It also has a significantly cleaner piston head - don't believe I saw any evidence of burning oil in there.

Cylinder 4 - kinda nasty
Cylinder 4 also has some burnt oil - not as much as 1, but a little more than 2. This picture also appears to show a vertical score to me.

The cylinder walls are suspect in places. Here's one place I think I see a vertical line and maybe some ridging.

**KiwiAlfa156** · 08-28-2025, 06:08 PM

Hi Seinwave

My two cents is that you want to be 100% certain of the source of the oil leaks. Disturbing good joints that aren't leaking can lead to that joint leaking. Including if you aren't fastidious in your gasket replacement. The likelihood that it the leak has just started, its coming from the last thing you disturbed. Note, oil leaking and oil weeping are to my mind different. Once outside the engine, gravity (and wind while riding) will move oil around. So oil around the base of the barrels doesn't automatically indicate that this is the source.

A head gasket oil leak (if you have one) isn't an indication of the condition of your rings. Smoke is oil being burnt in your engine, i.e. poor oil control. Leaked oil is outside your engine so isn't likely to be related. Oil under pressure only passed though the head gasket on the 4 outer head studs which use the barrel stud holes as oil galleries. So leaks happen in these areas. If you get oil weeping at other areas around the head gasket it is likely capillary action between the gasket and the mating surface after 40 years of heat cycling.

If smoke, and excessive oil consumption (probably?) is the issue you wish to address, then pulling it apart and inspecting it and repair is the solution. The oil leaks should be dealt with by careful reassembly.

I did my Katana 650, a few years ago. https://www.thegsresources.com/_foru...ild-historical

Your plan looks good. If it were me, I'd do everything, to ALL cylinders while its apart. because this you opportunity to do all of it. There's not advantage in doing 2 cylinders only. That's doing half the job.

Ring/hone, valves lapped (by hand NOT by using an electric drill) and fresh stem seals (you have to remove the valve spring to lap the valves anyway), clean the pistons, you have to have clean grooves for the new rings, wrist pins are unlikely to be worn, so just new clips. Measure the piston/cylinder, ring/land clearances, set the ring end gap. Don't forget the barrel o'rings. Personally I'd get the head and barrels refaced at a machine shop to ensure that the new head gasket get the best possible life. Make sure that all mating surfaces are grease and oil free before putting on gaskets.

**seinwave** · 08-29-2025, 08:24 AM

Yeah, I didn't go into detail, but I had a "oh no the cylinder gaskets are leaking!" scare the previous (first) time I adjusted the valves and replaced the cover gasket. That was my first introduction to the labyrinthine design of the valve cover and cylinder head air and drain paths - which I am increasingly convinced was designed by a trickster god moonlighting as a junior engineer who wanted to create the most diabolical puzzlebox ever widely distributed to the human race - and how they make it easy to mistake a leak from one place for a leak from another.

That time it turned out to be a sorta-hard-to-spot oil leak from the cover, which I patched up with the finest in Permatex gunk. That experience, plus the fact that I know the head-to-cover interface is not in the greatest shape (among other things: the thread on two thru-holes have turned to chalk and I've had to construct a sort of undersized-bolt-squeeze fastener; two more are jammed tight with what I know is a bolt but could pass for solid titanium plugs), made me think I was smart enough to distinguish cylinder leak from cover leak. But I think it just made me a smart mark.

I was VERY sure when I made this post that I'd made 100% certain it was the cylinders this time. I'd cleaned the engine twice, identified and rectified many a leak from the valve covers, gone on many small diagnostic rides, etc. So when I saw oil still pooling at the little divot between the starter cover and the cylinder, and (for all appearances) welling from the little prow under the exhaust pipes at the front, AND still collecting right on the engine fin under the head gasket at a few places, AND I couldn't find the drip, I was pretty sure I'd isolated it.

And then, the day after making this post, I went down to see if there was a blockage in the breather cover, and found evidence of yet ANOTHER little drip path down the back that could hypothetically explain all that. The trickster god may have gotten another notch on his belt.

That's a lot of writing to say - yeah now I'm not sure.

The information you give in your post probably points more towards the "no" side, too. I was somehow under the impression that the pressurized oil thru the head gasket was passing through four of the smaller inner stud (?) holes. The "evidence" of head gasket leaking I saw was more towards the middle-side of the cylinders, away from the big studs, which points toward it not being a leak of pressurized oil. I also think I would have seen evidence of the capillary action you mention more consistently through my ownership.

I didn't make it clear, but I wouldn't say it's consuming oil excessively (or at all), and it's not really "smoking" in the classical bad-rings way. The only symptom is an embarrassing tendency to smoke out of the left pipe on cold starts. It puts out quite a bit of smoke (and it's definitely oil smoke) but I've never seen any smoke once the bike is warmed up or on the way. It's bad enough I'd want to fix it if the top is coming apart, but not bad enough I want to take the top apart to fix it. I thought maybe the smoke could be a distinguisher as to how (some) oil is getting to the head gasket in the first place, not that it indicated an oil leak.

Good info on lapping the valves by hand; I had planned to use the cordless-drill-and-a-piece-of-rubber hose technique.

Writing all this is making me think (presuming I am able to strongly rule out a bad base gasket): maybe I should source a used cylinder head that doesn't have the aforementioned chalk-thread problem, slowly build it up on the bench over the winter or so, and then do a transplant with a top-end rebuild at the next valve adjustment interval. I don't mind doing work the right way, but like you mention, I really do mind tearing open good-enough work to unnecessarily fettle (and potentially cause more problems).

**oldGSfan** · 08-29-2025, 08:38 AM

Way back in time, I had my '82 GPZ1100's cylinders measured and honed, and I put in new rings. I was crushed when it blew smoke just as badly. What a pain. Took it all apart and put in 1165 Wiseco pistons/rings, and it was perfect. Really soured me on honing, as I did nothing wrong. It's the only engine job in all my years that I failed. Maybe they didn't measure, who knows. Hope yours works better than mine.

**Buffalo Bill** · 08-29-2025, 08:48 AM

Have you looked down the intake ports at the valve tops?
1st on you list should be a valve job including: new stem seals, replace valves with corroded edges, all lapped in and new springs.

**Nessism** · 08-29-2025, 09:36 AM

Oil smoke on start up = time for a teardown = welcome to the 40+ year old motorcycle club

You will learn much during the process. That also is part of being in the club.

Roll up your sleeves and enjoy the ride. There are lots of us around here that have done similar, so help is at the ready to answer your questions.

**KiwiAlfa156** · 08-29-2025, 04:10 PM

May be some photos of where the oil is leaking? Also if the 6 mm to cam cover bolt holes are stripped, the correct (best and permanent) fix is to use a thread insert. You do need all of these bolts torqued evenly to the correct torque for the gasket to work as intended.

You can do thread inserts yourself. There's bound to be numerous YouTube how to's. Carefully drilling straight and proper use of a thread tap (using grease to catch swarf and alloy chips -you obviously need to keep these out of your engine- and your done.

**seinwave** · 08-29-2025, 07:38 PM

Originally posted by Nessism View Post

Oil smoke on start up = time for a teardown = welcome to the 40+ year old motorcycle club

You will learn much during the process. That also is part of being in the club.

Roll up your sleeves and enjoy the ride. There are lots of us around here that have done similar, so help is at the ready to answer your questions.

Thanks, but this isn't really my entry into the club - no beginner's luck for me. This is my third bike, second GS, and third or fourth (or fifth?) major repair project.

Originally posted by KiwiAlfa156 View Post

May be some photos of where the oil is leaking? Also if the 6 mm to cam cover bolt holes are stripped, the correct (best and permanent) fix is to use a thread insert. You do need all of these bolts torqued evenly to the correct torque for the gasket to work as intended.

You can do thread inserts yourself. There's bound to be numerous YouTube how to's. Carefully drilling straight and proper use of a thread tap (using grease to catch swarf and alloy chips -you obviously need to keep these out of your engine- and your done.

I can certainly show you where I saw oil on the engine during and after my diagnostic rides....
left%20side.jpg

(these aren't up to date - think this was before I zeroed in on the gaskets as an issue, but after I'd cleaned the engine up a little, but before I cleaned it up properly. So if you see oil, it's not necessarily where the current suspected leaks are, and if you see gunk or any other signs of poor maintenance - it definitely isn't there any more and it's also from the previous owner and also no you didn't and uh...)

...but that won't really answer the question of where that oil came from. Guess I'll have to go on another little ride - oh no!

(also while I'd love it to be the CCT gasket - careful observation seems to have ruled that out.)

On the topic of timeserts - not to get away from the topic (top end rebuild advice) but I've been turning that over in my head since this last valve rebuild and I don't think it's a good use of time (and secondarily money). If these were threads I'd lost to too many ugga-duggas, or that I knew the PO had over-ugga-dugga'd, it would be - but the two I lost myself just slipped right out when I was installing new hardware at a very very light torque. It's really like those two turned to chalk. So I suspect the rest are living on borrowed time. And when I add up the time (and I guess the cost, but once you have the kit the inserts are pretty cheap) up of doing at least four bolts, I think it's better spent finding a head that isn't perishing and building it on the bench. This goes double if I find something wrong with the valves that require replacing parts, triple if (god forbid) I find the threads on the camholders or other internal parts to be in a similar state. And I *know* I can get the valve cover to seal properly (if not prettily) - that's how it was before this valve adjustment.

Originally posted by Buffalo Bill View Post

Have you looked down the intake ports at the valve tops?
1st on you list should be a valve job including: new stem seals, replace valves with corroded edges, all lapped in and new springs.

I haven't, good idea! The pipes are coming off for fresh connectors soon, so I'll also be able to look down the exhaust valve.

Do you follow the criteria in the service manual for replacing the springs, or do you think it's worth just going ahead and swapping the ones in there (which must be 40-year-old)?

**Cipher** · 08-30-2025, 07:40 PM

One piston top looks eroded possibly preignition?
the oil will stop leaking when you replace the gaskets.

**seinwave** · 08-30-2025, 09:25 PM

Originally posted by Cipher View Post

One piston top looks eroded possibly preignition?
the oil will stop leaking when you replace the gaskets.

I'm now realizing one of my edits ate an important part of my original post. Yes, I saw some evidence of detonation (I assume you're talking about cylinder 1?) - there's one or two small circular divots (seems to mostly be in the carbon layer?) that absolutely refused to show up on camera.

**first timer** · 09-03-2025, 03:59 PM

Nothing looks to out of the ordinary. Just standard carbon build up. If the Bike was run with a poorly tuned/cleaned carb you can get carbon build up from running rich. The piston edges and walls look fine. Your valve stem gaskets are probably hard and letting oil suck in on decel, it's a pretty common issue. You can change the valve stem gaskets without pulling the motor apart. If you are feeling froggy run a little marvin mystery oil in your oil to help clean up piston rings and oil rings.

If you are just looking at getting it operational, then i would rebuild the carbs, replace the intake boots and o-rings and give the motor a good pressure wash, it's pretty crudy so it's hard to tell where all the oil is coming from.

Then run the bike for a while, beat on it and give her some rpms and then do another scope and see what it looks like.

If you are hell bent on doing gaskets, plan for base and head gaskets and take the cylinder and head to a machine shop to have them fly cut the head surfaces for a perfect sealing surface. A lot of times DYI folks do a poor job cleaning surfaces or use the wrong tools cleaning surfaces and make things worst.

**lizzywhite45** · 09-04-2025, 02:54 PM

Sounds like you’re digging in the right spots. If you’re opening it up, I’d just do all four cylinders while you’re in there, rings, hone, valve seals, lap the valves. It’s not worth doing halfway.

Head and base gasket leaks can definitely be sneaky, but if it’s coming apart, might as well clean everything up right. Check clearances, get the head and barrels resurfaced if needed, and take your time on reassembly.

You’ve got a solid plan. Keep at it. These old motors reward the effort.

**seinwave** · 09-07-2025, 03:48 PM

Originally posted by lizzywhite45 View Post

Sounds like you’re digging in the right spots. If you’re opening it up, I’d just do all four cylinders while you’re in there, rings, hone, valve seals, lap the valves. It’s not worth doing halfway.

Head and base gasket leaks can definitely be sneaky, but if it’s coming apart, might as well clean everything up right. Check clearances, get the head and barrels resurfaced if needed, and take your time on reassembly.

You’ve got a solid plan. Keep at it. These old motors reward the effort.

Originally posted by first timer View Post

Nothing looks to out of the ordinary. Just standard carbon build up. If the Bike was run with a poorly tuned/cleaned carb you can get carbon build up from running rich. The piston edges and walls look fine. Your valve stem gaskets are probably hard and letting oil suck in on decel, it's a pretty common issue. You can change the valve stem gaskets without pulling the motor apart. If you are feeling froggy run a little marvin mystery oil in your oil to help clean up piston rings and oil rings.

If you are just looking at getting it operational, then i would rebuild the carbs, replace the intake boots and o-rings and give the motor a good pressure wash, it's pretty crudy so it's hard to tell where all the oil is coming from.

Then run the bike for a while, beat on it and give her some rpms and then do another scope and see what it looks like.

If you are hell bent on doing gaskets, plan for base and head gaskets and take the cylinder and head to a machine shop to have them fly cut the head surfaces for a perfect sealing surface. A lot of times DYI folks do a poor job cleaning surfaces or use the wrong tools cleaning surfaces and make things worst.

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.

**first timer** · 2025-09-09T00:15:47

Originally posted by seinwave View Post

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.

There are machine shops that make metal widgets for industrial purposes and there are machine shops that specialize in automotive/powersport repairs.

You want a automotive machine shop. To find a reliable one i would stop by your local independent automotive repair shops and/or motorcycle shops and ask the guy who turn the wrench who they send their heads to for machine work. If they are dicks they will try to get you to let them do the work and send it out on your behalf, if they are cool they will tell you go see XYZ and tell them Bob sent you.

Here is a example of a local shop by me that could take on the work. https://larrysengine.com/services/

Most automotive machine shops will know what you mean by fly cutting, or decking the head and cylinder or resurfacing the head/cylinder and will likely suggest that to you without being prompted once they see your head and cylinder. Basically you just want them to clean the surface and not remove a ton of material, you aren't looking to bump up the compression. If you are running stock cam you will have plenty of room even if they do a deep cut, and shouldn't need to worry about stock pistons and valves making contact.

Here is an example of what you are after.

https://www.youtube.com/shorts/Kc5CE77medI?feature=share

If you want to nerd out and learn a few things watch these guys, father and son team who run a automotive machine shop and do things the right way. (aka measure 3 times cut once)

https://youtu.be/BGH78hbsN5A

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

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

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