Out riding with the wife in the country. I looked down and saw a small puddle of oil forming on the motor behind the head (left side). Looks like I'm going to need to install a new cylinder base gasket.....uuuugh.... X I feel this level of work is beyond my mechanical skill set. Anyone know if a good mechanic that would take it on? I'm in Florida and the bike is a 1980 GS850.
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Cylinder base gasket replacement
- Thread starter kikdrum18
- Start date
Before going with a gasket replacement check the head stud nuts. Sometimes it can be the easy things that fix a problem, not always of course. Checking the head stud nut torque before diving into a gasket could be the solution, will only cost you a few minutes and no money.
It’s also well worth your time so see exactly where the leak is coming from. Degrease/wash and thoroughly dry everything. Spray the whole area with powdered foot spray. Run the engine a look closely to see what gets wet first. The leak may not be coming from where you think. Could be anywhere above your puddle, even on the front of the engine.
Excellent advice! Thanks. A mechanic friend suggested the same thing but said to remove the valve cover to access the other head studs as well. It would be great if that solves it.
I'll definitely try that too. Foot spray is much cheaper than the alternative.????
Going straight from leak-free to a puddle is unusual for a base gasket leak.
However, in the 850 a base gasket leak will surely happen, sooner or later, but it usually starts with a slight oil misting or weep that gets dirt sticking to it, long before it gets to actually leaking. Iow, you get plenty of warning that a head and barrels removal is in your future.
Mine have always started the slight oil misting from 30K to 50K miles, and there's been at least another 10K miles before I finally did something about it.
All the head studs are accessible without taking the valve cover off.
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Thanks Grimly. So you're saying the 4 exposed nuts close to the spark plugs are all?
I do have a bit of research to do to verify the leak, but the only place I'm seeing it is on the bottom left rear side of the head and base. Seems to only leak when the bike is under power.
Like I said, more research...
I did find a mechanic and rough estimate of 1.5k. I'd do the work myself, but uncharted territory could be even more expensive.
I do have a bit of research to do to verify the leak, but the only place I'm seeing it is on the bottom left rear side of the head and base. Seems to only leak when the bike is under power.
Like I said, more research...
I did find a mechanic and rough estimate of 1.5k. I'd do the work myself, but uncharted territory could be even more expensive.
For $1.5k you can buy a lot of tools! 
For $1.5k you can buy a lot of tools!
And be a TV repairman like Specoli's dad... ????
No, there are another few inboard of those, you'll need to take the tank off.
Absolutely no reason not to have a manual with all the torque specs.
Bookmark this site.
https://gsarchive.bwringer.com
Bookmark this site.
https://gsarchive.bwringer.com
If I'm imagining what "on the motor behind the head" means right, I think you're likely experiencing an issue with the valve cover gasket (or possibly the valve cover itself, but probably the gasket).
There's a series of drain passages built into the valve cover and the head that make it very easy for a leak in one part of the mating surface to cause oil to show up on another part of the head, often one you'd NEVER intuitively connect to the actual source of the problem.
I have a valve cover with a couple boogered bolts, and come valve adjustment time I always end up chasing down similar issues to this.
I'm going to guess that you are leaking oil on the "inside" of the U on the left side of the valve cover, way back under the tank. There's a drain hole behind the #2 spark plug that leads to the back of the engine; oil that leaks from this area will drip down the back and often along the cooling fins, getting everywhere.
If you peek in there, I bet you'll see evidence of dripping oil. If not, clean the engine and run it until you notice the pooling again, and I bet you'll see a trickle of oil matching my description.
Tightening down the head is not a bad idea, but if that doesn't fix it, check the torque on the valve cover bolts. If *that* doesn't fix it, try a new valve cover gasket. And if *that* doesn't fix it, and you can see oil... all I'll say is Permatex The Right Stuff 1 Minute not only works wonders if beaded onto a dripping gasket and smeared out with the handle of a plastic fork, it also lasts for at least a valve adjustment interval, comes off clean, and keeps your engine dry for a few minutes of work.
Here's a really bad diagram of what I think is happening. The yellow line is supposed to indicate the mating surface between valve cover and head. I think your engine will look a little different, but generally the same idea applies.
There's a series of drain passages built into the valve cover and the head that make it very easy for a leak in one part of the mating surface to cause oil to show up on another part of the head, often one you'd NEVER intuitively connect to the actual source of the problem.
I have a valve cover with a couple boogered bolts, and come valve adjustment time I always end up chasing down similar issues to this.
I'm going to guess that you are leaking oil on the "inside" of the U on the left side of the valve cover, way back under the tank. There's a drain hole behind the #2 spark plug that leads to the back of the engine; oil that leaks from this area will drip down the back and often along the cooling fins, getting everywhere.
If you peek in there, I bet you'll see evidence of dripping oil. If not, clean the engine and run it until you notice the pooling again, and I bet you'll see a trickle of oil matching my description.
Tightening down the head is not a bad idea, but if that doesn't fix it, check the torque on the valve cover bolts. If *that* doesn't fix it, try a new valve cover gasket. And if *that* doesn't fix it, and you can see oil... all I'll say is Permatex The Right Stuff 1 Minute not only works wonders if beaded onto a dripping gasket and smeared out with the handle of a plastic fork, it also lasts for at least a valve adjustment interval, comes off clean, and keeps your engine dry for a few minutes of work.
Here's a really bad diagram of what I think is happening. The yellow line is supposed to indicate the mating surface between valve cover and head. I think your engine will look a little different, but generally the same idea applies.
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Seinwave, thank you for the detailed comment. Lots to consider there.
I previously had a leaking oil pan gasket that I'm replacing as soon as it arrives. Once that's done, I'll deep clean the motor, use the powder foot spray Rich suggests, and examine the area you suspect as well. I did look there last night and saw no evidence of oil. That doesn't mean it's not happening as it's hard to see without closer inspection.
Regardless, and as Grimly stated, "sooner or later...."
As much as I love the bike, it's probably worth it to have all top end gaskets (including the cylinder base gasket) replaced. Other than what I'm dealing with, this bike is nearly perfect for a 45 year old. It seems most repairs and upgrades for it are relatively inexpensive and within my limited capabilities.
I really appreciate all the input and knowledge. I'll keep you posted.
I previously had a leaking oil pan gasket that I'm replacing as soon as it arrives. Once that's done, I'll deep clean the motor, use the powder foot spray Rich suggests, and examine the area you suspect as well. I did look there last night and saw no evidence of oil. That doesn't mean it's not happening as it's hard to see without closer inspection.
Regardless, and as Grimly stated, "sooner or later...."
As much as I love the bike, it's probably worth it to have all top end gaskets (including the cylinder base gasket) replaced. Other than what I'm dealing with, this bike is nearly perfect for a 45 year old. It seems most repairs and upgrades for it are relatively inexpensive and within my limited capabilities.
I really appreciate all the input and knowledge. I'll keep you posted.
Then as you’d have the barrels and head off, you got to ask your self, should I just go ahead and replace the piston rings and valve seals? There are seemingly endless “while I’m at its”.
Sorry. Not sorry. 
It’s just that I was where you are 2 years ago. It wasn’t an oil leak. I put a hole in a valve. Reconditioned a used head, lapped valves, replaced rings and valve seals, honed barrels. It wasn’t terribly expensive for the parts. Just a lot of work, most of which I had no experience doing. Good folks here encouraged and helped me whenever I got stuck.
But, we’re getting ahead of ourselves. Find the leak. Could be a very simple fix.
It’s just that I was where you are 2 years ago. It wasn’t an oil leak. I put a hole in a valve. Reconditioned a used head, lapped valves, replaced rings and valve seals, honed barrels. It wasn’t terribly expensive for the parts. Just a lot of work, most of which I had no experience doing. Good folks here encouraged and helped me whenever I got stuck.
But, we’re getting ahead of ourselves. Find the leak. Could be a very simple fix.
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I'll be investigating tonight, but the leak may be coming from the cam tension adjustment gasket. That would explain a puddle on top of the case.
I tried to download the Bike Cliff's manual with no luck.... stupid computer.
Anyone know what's involved in removing the cam tension adjuster if that happens to be the issue? I was told the first step is getting the engine to top dead center, otherwise it will not go well.
I tried to download the Bike Cliff's manual with no luck.... stupid computer.
Anyone know what's involved in removing the cam tension adjuster if that happens to be the issue? I was told the first step is getting the engine to top dead center, otherwise it will not go well.
My opinion, you don't realize how much you need a repair manual, of some kind, for your bike. You may be like me, the computer stuff can get me confused. for me a Factory manual is best, Clymer 2nd, and Haynes 3 rd. but all are good... The tensioner removal is pretty simple, but reading it with drawings is by far better than somebody explaining it to you... I don't remember anything about having to get on Top Dead Center to remove, replace, or fix the tensioner.