'79 GS1000 head gasket replacement

[sdbuchert]

About 2000miles/1.5 years ago, I had my GS1000's top-end apart for inspection. I put it back together with a non-Suzuki head gasket, and of course it leaks. I bought a new Suzuki head gasket for this time around, and I am wondering if I need to replace the base gasket between the cylinder block and the crank case at the same time I replace the head gasket. The base gasket was replaced with the head gasket when I had the top-end apart last time. Anyone successfully (leak free) replaced a head gasket without replacing the base gasket too? I feel like I should just replace the base gasket at the same time so as not to chance wasting a new...and expensive...head gasket. Thanks for your comments.

[feelergaugephil]

I changed my head gasket out without changing the base gasket, BUT, if you prize up the bores, you will HAVE to change it.

[hampshirehog]

As usual....it depends. If your cylinders have become 'stuck' to the base gasket/ crankcase and you didn't have to tap the head off (i.e. it just lifted off cleanly) there's a stong probability that the base gasket will be ok. I've done this a few times successfully, but bear in mind this is on UK bikes that have been dosed in salt for years and only because the cylinders can be right b*stards to get off.
If your cylinders are easy to pull, or you have any doubts, I'd suggest changing. It's an easy enough job to do - as long as the cylinders haven't salt welded themselves on!

[Big T]

I wouldn't be worried about changing the base gasket.

It is generally recommended to replace the base gasket when pulling the head gasket because it has been in place 20+ years. The base gasket has then hardened up and can break when the head is removed.

After 2 years, the base gasket should be pretty pliable, and, if you greased it, it shouldn't stick to the barrels.

Also, The head should just pop off and not have to be hammered off. Less force on the base gasket.

So, replace the head gasket and be done with it

[Agemax]

surely it is false economy? if you got your head off anyway, buy a top end gasket set and replace the base gasket at the same time.
why go through the grief/expense/ time of putting your head back on, cams in, timing it up, then putting all the rest of the bits back together then after a few miles finding your base gasket weeping oil! then having to strip it all out again and having to fit a new gasket.
doesn't make sense to me, if it was a clutch cover then yes i would risk it with a good clean up if the gasket came off ok and maybe a smear of hylomar but dont risk it with the top end of your engine.

just my opinion!

[tkent02]

So then rehone the cylinders too?
I would any time the block comes off of the pistons.
My bike, if it didn't leak before, and if the cylinder remains stuck to the cases, I'd leave it alone.
If the cylinder does come loose, I'd replace the gasket, which requires removing the cylinder block. To me that would require honing the cylinder again, and and breaking the engine in once assembled, as if it was a complete rebuild. (run it hard)

[Nessism]

What brand of head gasket failed, and what type of gasket was it - fiber composite, MLS, or ?.

I recently bought a gasket kit for my 1000 and went with Athena because they use a MLS head gasket that has a skim layer of viton rubber on top and bottom. Fingers crossed that the seal is going to be OK. Cost for the entire kit was $65 shipped vs. $70 for a Suzuki head gasket alone.

[Agemax]

So then rehone the cylinders too?
I would any time the block comes off of the pistons.
My bike, if it didn't leak before, and if the cylinder remains stuck to the cases, I'd leave it alone.
If the cylinder does come loose, I'd replace the gasket, which requires removing the cylinder block. To me that would require honing the cylinder again, and and breaking the engine in once assembled, as if it was a complete rebuild. (run it hard)

why do you need to hone the cylinders if you just take the block off to replace a gasket?
you may think the block remains stuck to the cases but you have released all the torque pressure squeezing it down and it is now in a precompressed state, a gasket seals by compressing between 2 surfaces and forming a leak tight seal. once a seal is broken you cannot guarantee it will seal again.

personally i wouldnt take the risk but others may do

[tkent02]

why do you need to hone the cylinders if you just take the block off to replace a gasket?

Don't think there's much chance of getting the rings back in exactly as they were.

you may think the block remains stuck to the cases but you have released all the torque pressure squeezing it down and it is now in a precompressed state, a gasket seals by compressing between 2 surfaces and forming a leak tight seal. once a seal is broken you cannot guarantee it will seal again.

personally i wouldnt take the risk but others may do

Hasn't leaked on the few I've done this to, but it's only been a few. Again, if the block moves at all on the cases it's coming off.

[hampshirehog]

personally i wouldnt take the risk but others may do

I'd agree - but sometimes if you've got an old flogger and the barrels have become welded on you can be in serious trouble trying to get them off. In that case I reckon it is worth the risk. (Avoids loads of cursing)

If sdbuchert did a top end rebuild only a few miles ago (and not 50k / 30 years ago) he won't be in that boat though.

[sdbuchert]

What brand of head gasket failed, and what type of gasket was it - fiber composite, MLS, or ?.

I recently bought a gasket kit for my 1000 and went with Athena because they use a MLS head gasket that has a skim layer of viton rubber on top and bottom. Fingers crossed that the seal is going to be OK. Cost for the entire kit was $65 shipped vs. $70 for a Suzuki head gasket alone.

Nessism,
Im not sure what brand of gasket I used, but I will look and let you know.


I think I will probably replace the base gasket at the same time just to be safe, BUT........

As far as honing the cylinders... When I had the top end apart last time (head and cyclinder block off) to replace a weaping base gasket and fix 2 broken exhaust bolts from the previous owner, the bike had 18,000 miles on it and I didn't hone the cylinders. The bike runs great, doesn't burn any oil, and has great compression. Maybe I just got lucky? I'm wondering if its worth the cost of honing. How much $$$ is it? Thanks everyone for your insight.

[Nessism]

I thought honing was only required when changing the rings, not each time the cylinder is removed. As long as the rings are not distrubed too much during R/R of the cylinder, I think you are safe to skip the honing.

[Agemax]

I thought honing was only required when changing the rings, not each time the cylinder is removed. As long as the rings are not distrubed too much during R/R of the cylinder, I think you are safe to skip the honing.

correct, honing is not required when lifting the block just to replace a gasket, maybe worthwile if its a long time since the block was off and the bores look slightly worn, a new set of rings would not be a bad idea either if you want to be sure.
as long as the pistons look ok with no excessive scoring then everything should be ok

[Big T]

I thought honing was only required when changing the rings, not each time the cylinder is removed. As long as the rings are not distrubed too much during R/R of the cylinder, I think you are safe to skip the honing.

Agreed, at 18k there's no reason to hone the bores. Just make sure the ring ends are staggered on each piston before putting the barrel back on.

[Nessism]

Agreed, at 18k there's no reason to hone the bores. Just make sure the ring ends are staggered on each piston before putting the barrel back on.

I'd try to put the cylinder down with the rings in the same position as before...as long as the gaps are not in-line. I think you have the best chance to maintain the same cylinder seal as before that way.