Non OEM, after market gaskets.

[nickjtc]

Now that non-riding season is here (aka winter) I'm in the process of working on 'Old Faithful', the '77 GS750 with a determined view to getting it on the road again next year. It's been an interesting project, especially since a) I restrained myself from tearing the whole bike apart (and therefore probably ending up looking forever at boxes of bits) and so am refurbishing bits and pieces one by one and b) I'm doing stuff that I have never had to do to a bike.

Anyhoo, to the point. The cylinder head is off to look for a reason why, under the ownership of the second owner, the bike developed an oil leak to coat the front of the engine with a layer of ugly mung. No obvious reason, so far, why this should have happened. The crowns of the pistons and the combustion chambers were quite carbon'd up which involved much travail with scraper/Gunk and Scotchbrite pads.

When it comes to re-assembly, all of the various gaskets will need to be replaced. Should I be a tight wad and go for Athena or Vesrah after-market products, or buck-up and get OEM where they are still available? Anyone had any experience with non-OEM gaskets??

Than q. Nick

[JayDub]

Vesrah?  Used them many times, they're ok. Oil leak- the 10 mm bolt on the front of the head is usually the culprit, I never got mine to stop leaking, even with a longer bolt + nut

[Bixxer Bob]

For what it's worth, Clive Woods said "Why would you put a lot of hours into an engine out /strip / rebuild /in and then skimp a few quid on "pattern" parts which might mean doing it all again???  He's a fan of OEM parts ie the bits the manufacturer used but from cheaper sources, but not of patterns unless the original is no longer available.

[nickjtc]

Vesrah?  Used them many times, they're ok. Oil leak- the 10 mm bolt on the front of the head is usually the culprit, I never got mine to stop leaking, even with a longer bolt + nut

There are so many differing opinions to be read, out there. Either after market is cr@p or it's the best thing since sliced bread. I tend to prefer OEM stuff, if it is still available. The 30% extra is worth it, if you only have to do the job once. The whole issue with this particular job is that Suzuki no longer lists the cylinder head gasket as being available. Fortunately there is always eBay to default to!

JayDub: which of the 10mm bolts is the usual culprit? There was no evidence of leakage from any of them when I took the head off.

[JayDub]

At the front of (and part of) the cam chain tunnel, there's a rectangular piece with a 10mm bolt through it protruding from between the headers its one of the head bolts... its a common leak on the 550/750 motors and not always easy to tell if its leaking, but oily crud above/below is a good indication, and some HT silicone usually helps. It doesn't leak a lot, but it makes a mess of a shiny motor.

[nickjtc]

Thank you.

My bike has the earlier two valve-per-cylinder engine, which does not have that extra bolt. Although the two outer dowel pin orifices might be suspect...??

You are right, it's amazing how even a tiny bit of on-going leakage can make such a mess of an air cooled engine.

[JayDub]

Well that won't help much then....... sorry Nick old chap! - (I'd still use silicone though )

The dowels shouldn't come into it, and they don't bottom out, but you would make sure they were cleaned out any way.

Other than the head, the cam cover is well known for leaks and particularly the tacho drive 'O' ring

[nickjtc]

and particularly the tacho drive 'O' ring

I will explore that, too, thanks.

[nickjtc]

Other than the head, the cam cover is well known for leaks and particularly the tacho drive 'O' ring

All things are pointing to this being the culprit. There is no sign of leakage around the main gaskets, which tends to eliminate them. The O ring in the rev counter take-off is quite hard, so will be replaced and the whole mechanism put back together with a skiff of hi-temp silicone.

[JayDub]

Its worth going for a Viton o ring Nick... they resist heat much better, infact when ever I replace o rings they're my preferred choice, I don't think there's anywhere they can't be used (wait for it) but I've not had any come backs. 

[nickjtc]

Job done. The piston crowns and valves/combustion chambers now look spanky and clean. I found a set of OEM gaskets on eBay, including the head gasket, for a good price. I had to re-shim 5 of the valves; way to wide a gap. My local dealer does not do an exchange programme so I had to buck up and pay full price.

Next and final job is to repaint the tank and tail piece and she's good to go..... assuming that I put everything back together correctly :icon_wink:

PS the only culprit for the oil leak was the tach drive so both seals have been replaced.

[JayDub]

I just remembered that when ever I top-ended my GS's, no matter how carefully I lined up the cam sprocket arrows horizontally with the head, I always found the timing a tooth out, and it woudn't fire... no-one else seemed to have a problem - I just learned to expect it 
And not seal or tighten the cam-cover til it was confirmed as firing 

Well done Nick... I wish I still has my 550e - proper all rounder and workhorse.

Evolution of 17yrs/179k mls...
(the last one was taken in 07 but I still had her, looking pretty much the same in 2013)

[nickjtc]

I just remembered that when ever I top-ended my GS's, no matter how carefully I lined up the cam sprocket arrows horizontally with the head, I always found the timing a tooth out, and it woudn't fire...

Hmmm. So the piston crown and valves must be "non-contact" then. That's good to know. I wouldn't want to have catastrophic damage due to my inaccuracy of re-assembly.

[JayDub]

Not AFAIK, but you wlon't forget to do the valve stem oil seals will you Nick

[nickjtc]

Not AFAIK, but you wlon't forget to do the valve stem oil seals will you Nick

Oh bollocks. I knew there was something else I needed to look at.....