GS550: About oil leaks and resealing the top end

[Scott S]

I have a 1980 GS550 that came to me with a filthy, oily mess all over the engine. Mostly around the head and cylinders, mostly towards the rear of the engine.

It has less than 30k miles on it. When I first joined the site I asked about a source for rings and was told "Why? These engines are good for 100k and rarely need it".

My preference is to replace the base gasket any time you remove the head gasket. I have gotten away with NOT pulling the cylinders on a couple of CB500's and replaced a weepy head gasket.

My questions are:

* What are the usual suspects for oil leaks on a GS550? The area around the cam chain tensioner was HORRIBLE. The carbs weren't so bad, so that leads me to believe that the leak was from lower.

* Since the lower case wasn't very oil fouled at the front of the bike, I think the cylinder base gasket might be OK. How do you feel about just doing the cam chain tensioner and everything from the head gasket on up?

* With 20-something thousand miles, I'm tempted to NOT disturb the rings and just take a chance....thoughts? When I first got here, I was told how robust these bikes are.

[Nessism]

Why not degrease the engine followed by carefully watching to find the source of the leak? Some guys use foot power spray after cleaning since that makes the leak stand out.

Regarding the rings, it's best to measure compression so you are not guessing about that either. Needless to say the valves must be adjusted first or you are just wasting your time.

Good luck

[scratch]

Well... you're going to have to clean it anyway so, clean, observe, measure etc...

[Scott S]

I should have added, the engine isn't running at the moment (or when I got the bike).
Its currently out of the frame and on the engine stand.

I've already cleaned it up pretty well and will hit it again while I'm working on the seals and gaskets.

So..... I can't exactly run it to check for leaks right now.

[scratch]

A 40 year old dried up base gasket that has delt with thermal expansion?
Replacing the rings is not mandatory if they are in spec... they will probably check out ok with that milage so, the question boils down to a smart-shopper 30$ gamble on a base gasket, the 2 o-rings & 4 circlips... (if you can borrow a ball hone...)


$30 buys you
1. the opportunity to check pistons and rings
2. the peace of mind that the ancient base gasket won't decide to leak as soon as motor is back in bike (or... the D'oh! Factor)
3. the chance to clean the cylinder nice and paint

[Nessism]

It's going to cost a hell of a lot more than $30 to crack that engine open and fix it right. You need base, head, valve cover, and cam chain tensioner gaskets. Valve stem seals, seals for the tach drive and cam chain tensioner, base gasket seals, and various other things. All w/ OEM gaskets if you want it to last.

[Scott S]

I already have a full gasket set, valve stem seals, etc.

Where are some known "leaky" areas? It wasn't obvious that it was coming from one particular place, but the cam chain tensioner was absolutely the worst.

[Nessism]

There are no known leaky areas. Most common leak source is the valve cover because people don't know how to service stuff properly; they don't replace the gasket or when they do they don't clean the surface properly. Since you have committed to tear down the engine it would make logical sense to replace every seal and gasket in the top end. There aren't that many. Biggest question mark is the rings since there is cost involved. And speaking of cost, most aftermarket gasket kits are junk, particularly Athena (green gaskets). Hope your gasket kit is the OEM Suzuki variety.

[scratch]

It's going to cost a hell of a lot more than $30 to crack that engine open and fix it right. You need base, head, valve cover, and cam chain tensioner gaskets. Valve stem seals, seals for the tach drive and cam chain tensioner, base gasket seals, and various other things. All w/ OEM gaskets if you want it to last.

Why skimp on the base gasket if you already are doing the head and the seals etc was the point.
$30ish extra beyond what he was already doing... only adding base gasket, circlips, 2 o-rings to the list.
A bargain to go the distance rather than try to leave the cylinder undesturbed .

[Steve]

My preference is to replace the base gasket any time you remove the head gasket. I have gotten away with NOT pulling the cylinders on a couple of CB500's and replaced a weepy head gasket.

Go with your preference.

You may have gotten away with it on a couple of Hondas, but you probably won't be so lucky with the GS. I have tried it myself and had to go back and do it over.

Since you already have the engine out of the bike, it would only make sense to replace everything. As others have mentioned, the valve cover gasket is common, as are the tach drive and the cam chain tensioner. Please note that your "full gasket set" probably does not include the cam chain tensioner gasket, and it certainly does not include the two o-rings inside the tensioner. They usually don't leak by 30k miles, but let's face it, it has been close to 40 years. For a few bucks extra, it's cheap insurance. Same thing with the tach drive. Just a few bucks for a seal and an o-ring will ensure no leaks there.

The piston rings should not be a problem, no need to worry about that, but while the cylinders are off, you can ensure that they do move freely on the pistons.

.