Top end rebuild.. how far to go?! (1980 GS550)

[Gadgetboy550]

Hi all,

Been reading around the forum trying to get some answers to my questions. I have a GS550 1980 which runs well, but has an oil leak around the head gasket and more specifically focused around the front middle of the engine, by the cam chain tunnel.

LEaking oil is most noticeable after a fast ride- when i pull in at a services i seem to end up in a cloud of smoke as the oil burns off the headers for a couple of minutes - not a good look! my frineds have also pointed out that under hard acceleration the exhaust fumes are slightly oily..

in preperation for a weekend of top end refresh, i have taken my valve clearances and compression tests, in order to see what you guys think and to see if its worth doing the piston rings 'whilst your down there'

Compression checks - Wide open throttle, warm engine, plugs out.

1 - 140PSI 2- 140PSI 3- 140PSI 4- 150PSI

bit of oil down the plug hole...

1 - 170PSI 2- 160PSI 3- 160PSI 4- 180PSI

Valve clearences (cold engine)

1- 0.05ex 0.09in
2- 0.09ex 0.07in
3- 0.09ex 0.04in
4- 0.12ex 0.09in

I was planning to do new gaskets, lap in the valves, replace stem seals, adjust valve clearances and call it a day. would anyone recommend otherwise?

Cheers!

Matt

 

[Gadgetboy550]

Also in terms of gaskets - would anyone be able to recommend for or against these brands? 'NE Brand' Vesrah and athena? they are all similar price and available for quick UK delivery.. any ideas welcome! i will call robinsons foundry tomorrow to see what they have in the way of OEM, but no doubt they will be out of stock or very pricey..

 

[Nessism]

Your compression is pretty good. Blue smoke under acceleration indicates poor oil control rings though. Not sure what to suggest other than measure everything carefully after you pull down the top end. If you decide to keep the old rings make sure to clean the oil control rings really well. Maybe they are coaked up which is causing them to malfunction somewhat?

OEM Suzuki gaskets are best. Vesrah are decent, and Athena are criminally bad. At least the green base gaskets are anyway. Never use those.

 

[qcktvr]

Hi Matt
I cannot imagine being that far in to it and not honing / deglazing the bores and replacing the piston rings..
You have quite a difference in those compression readings dry to wet.. think you might regret not replacing them..
Good luck

 

[eil]

Much of this is up to personal preference. Balance how much time and money you have with your desire (or lack of) to wrench on the bike. I personally lean towards less wrenching and more riding, but not at the cost of blissfully ignoring a problem. If it were my bike, I would:

1) fix the oil leak(s). Could be from any number of places but a very common one is the tach drive. Wipe the engine as clean as you can get it, run it for a while, see where it leaks from. Oil on the surface of the engine blows around quite a bit while underway, so you have to clean up what's there first to find the leaky area.

2) Go one size thicker on the #4 ex shim. Suzuki specifies 0.03-0.08mm. Going over a little isn't bad but 0.12 is a bit too much for my taste.

And then see where things go from there. Burning a little bit of oil under acceleration is not that unusual on these older machines and those compression numbers are too high to speak of worn-out cylinders or rings. It may be the case that when you ride hard, you're heating up places on the exhaust where oil has already been deposited earlier. (Or causing more oil to spring from wherever it's leaking.)

Again with the caveat that if it were mine, I'd fix the leaks and just watch the oil level and only bother digging in deeper if it looks like the bike is consuming a significant amount of oil.

 

[Gadgetboy550]

Hi Guys,

Thanks for the advice, much appreciated. Its my daily ride and i only have access to a workshop this weekend (the joys of living in london) - so need to get everything ordered today.

Robbinsons foundry have quoted around ?120 for the gaskets and seals, and ?50per set for rings. ?320 ish total. Owch.

I am not sure if i should opt for the Vesrah top end gasket set for ?40ish over the Suzuki ones.. i think doing the rings is worth while as I am already in there!

As i have no oportunity to break the engine down and measure the rings before ordering replacements, i wondered if someone could confirm my understanding of ring sizes? are Oversized rings for a barrel which you have rebored? or for a barrel which has been worn? i would imagine the rings are the sacrificial component and therefore if the barrel is in good condition but the ring gaps are a little big, then a new set of standard rings and a quick Hone, will fix the problem?


Cheers,

Matt

 

[qcktvr]

Hi Matt,
You are correct, oversize rings go with a rebore and new pistons, the standard size is whatt you need..

 

[Gadgetboy550]

Y

OEM Suzuki gaskets are best. Vesrah are decent, and Athena are criminally bad. At least the green base gaskets are anyway. Never use those.

Hi All,

Thanks for your replies, very helpful advice!!

Caught in a bit of a last minute.com mess. ordered the rings and piston circlips from robinsons foundry for delivery thursday.

Now i cant seem to find a vesrah topend gasket set online other than Poland which wont get here for Friday..

When you mentioned that the green Athena gaskets are tragic, is this the same sh*t as you mentioned?

http://www.ebay.co.uk/itm/Suzuki-GS...553?pt=LH_DefaultDomain_3&hash=item46375543f1

Not sure what other options i have as i have the workshop booked for the weekend coming..

Does anyone have any ideas or contacts worth trying first thing tomorrow? or do I lump it and get athena gasgets?

Cheers!

 

[tkent02]

If you are buying rings and such, and taking it all apart anyway, consider going a little further and put on a 650 top end. For a hundred bucks or so extra you get 23% more displacement, and a lot more power, well worth doing.

If I had your engine I wouldn't even take it apart just yet, fix the leaks, determine why it's smoking and ride it until a convenient time to do the work. Leaking at the cam chain tensioner will blow through to the front of the engine and look like something a lot worse. Valve cover leaks and tach drive leaks will do the same.

 

[Nessism]

The prime Athena offending gasket is the base gasket. The green gasket material Athen uses can not take the clamp load. You can use the head gasket but I'd supplement the kit with OEM base and valve cover gaskets.

In general I agree with the others. Don't assume too much regarding the leaks. Clean the engine of all grime, dry, then start the engine and watch for the leak source. There are various places these old bikes leak including the tach drive, valve cover, and cam chain tensioner. These leak sources can fool you into thinking the head gasket is gone. Best to put in a little work upfront to make sure.

 

[Gadgetboy550]

Hi All,

I cleaned the engine up last week and put talc all over the engine around the various gaskets and seals. As the engine warmed up i could see oil bubbling out of the head gasket, as well as around the tensioner gasket and worst of all between the two middle cylinders around the base and head gaskets around the cam chain tunnel.

Although the compression tests showed OK results, my logic is to replace the rings, hone the barrels and lap in the valves whilst im in there replacing the gaskets. I hope this seems sensible.. if i csnt get gaskets for the weekend i will postpone until a time when i have the right parts..

Thanks for the ideas and info on gaskets, the idea of a 650 top end sounds tempting... are there any parts of the 550 top end that are cross compatible?