Various cylinder head questions

[cWj]

Practical 1:  Is it a given, that if the head is removed, the head base gasket has been compromised and needs replacing?

Practical 2: Do coated metal gaskets always need sealant?

Practical 3: Is De-carboning pistons (aka - cleaning) worth it?

Fiscal : what's a reasonable price for a 96-00 cylinder head?

Curiosity: As there any differences between pre-01 heads & 01+ heads besides the mechanical tachometer gear?

[bmf]

Metal gaskets always need replacing, make sure to clean off the old coating that gets left behind on the head/barrel surfaces. Permatex gasket cleaner is great, but beware if spilt, it will strip the silver paint off the crank cases.

No sealant, they have the coating that acts as a sealant.

I cleaned,  not sure if necessary but it feels good;-)

I paid about 150$ for a 90s head (shipped from Texas;-))

Heads are interchangeable, just need to move over the tach blanking part. Mine went into a 2003.


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[cWj]

I'm asking whether the gasket between the crankcase and the head base (hope I have the names right) needs to be replaced if the cylinder head is the only part that was removed. The search box brought up a couple entries of folks saying that the act of taking of the head will likely cause some separation in the case gasket leading to leaks. I don't think that's the case with mine, but wondered if changing both gaskets was standard practice.

Tach blanking part? So your saying the cast wasn't changed? There's some thing that can be removed from a newer head to make it work with a mechanical tachometer without drilling??

[gsJack]

It's been common practice to replace the cylinder base gasket whenever the head is removed.  I replaced a leaking head gasket on a CM400 Honda twin some years ago and didn't replace the base gasket.  It always seeped a little oil after that but not enough that it couldn't just be wiped off when checking/filling the oil and I'm not too fussy about little things like that.

I had a sticking bucket about 9 years ago that resulted in a broken exhaust valve that required pulling the head on my 02 GS and I lifted the cylinders and cleaned the bottom of the cylinders and the top of the engine case and put in a new gasket.  It leaked, no actually just seeped a little bit about the same as the old CM400 did years before.  If I had to do it again I would leave the cylinders in place and not bother with the base gasket.  Your choice on that, there are different opinions.

By the way the 01-02 GSs had a mechanical tach drive same as the 89-00 ones.  What bmf said about a blanking piece when they used a head machined for a mechanical tach on newer bikes with an electric one was true for a while but after stock was used up they didn't machine the head anymore for the tach drive. Don't know when that was maybe someone else does.

Using a putty knife scraper and a hand held wire brush I cleaned all the carbon off the piston heads I could while cleaning the gasket surfaces.

Just saw your PM about sticking buckets and it's getting late so we'll talk about it tomorrow if you want my opinion on it.

[cWj]

So, up to 01, compatible. 02-04, crap shoot. 05+, get a new bike.

Thanks, Jack. I probably won't get back to working on bike until Thursday, so tomorrow is fine.  Just trying to get some ideas before I start bidding on/buying things.

[burning1]

Carbon buildup isn't really a problem on the GS500; as an air cooled engine, it runs hot enough to burn off any deposits you might have. I've been inside a few of these engines, and carbon has never been an issue.

Run some sea-foam through it if that makes you feel better, or simply ride the shaZam! out of it. Cracking open the engine invites a lot of problems with little reward in this case.

[The Buddha]

His valve bores - bucket holes in the head have got scraped up and they are binding to the buckets.
They should be removed and everything should be honed and polished to fit.

You can replace the whole head, but you would be better off cleaning yours up - that way you know its good.

Cool.
Buddha.

[gsJack]

So, up to 01, compatible. 02-04, crap shoot. 05+, get a new bike.

The 01-02 heads are the same and have the mechanical tach drive and same parts fiche. The 04-06 parts fiche shows the head machined for the tach drive with a plug for the hole.  The 07 parts fiche no longer shows the hole machined.  But previous discussions indicate the cutoff line was not that exact as heads in stock were used up before new ones without the hole were used.

I like Buddha's idea of fixing your present head by honing the bucket holes to repair the damage and restore a good exhaust bucket fit but since the buckets are now quite tight they might be hard to get back out, would be worth a try though.  You would need a valve spring compressor to remove the valves and springs.

About tight buckets, you said you can put a screwdriver in the tight bucket notch and hit it with a hammer and turn it a bit.  But the tight exhaust bucket I had that caused the broken valve when it stuck wide open one freezing cold morning was so tight I couldn't budge it hitting it that way with a screwdriver and hammer.  Yet I let it go for some time to see if it would wear in and be free cold since it would free up in a minute or less after start up as the head expanded faster than the bucket and was good for all day after that.

[cWj]

His valve bores - bucket holes in the head have got scraped up and they are binding to the buckets.
They should be removed and everything should be honed and polished to fit.

Righty got banged up by me and is tight now. Lefty is just tight without my influence. The right intake took some tapping to get back in, but is still loose to spin by hand.

I'm wondering:


- if there wasn't something impending valve-wise (the bike needed an adjustment badly when I bought the bike, mechanic said the exhausts were really tight; the LE cam lobe is definitely scored

- if the incessant warming-up and choking I have had to do while I had a weak battery/stator didn't heat those exhaust valves up

- if the left plug's tendency to be fouled has to with a stuck left exhaust valve.

- if this woman who I can't stop looking at that I'm currently working on a project with digs me or - wait...sorry, wrong section for that 

[The Buddha]

Lobe scratches are not going to cause a valve to burn. And scored valve lobe is beyond the scope of your problem and repair.  Valve lobe scratches dont matter. I watched my crows foot for 40K miles and all it did was slowly fade - but @ 48K I could still easily see it.

Oddly neither does the choking and warming up. By defninition burnming occours when its too hot. You do know it wont exactly burn - like you can burn a piece of paper right. Its steel, you can try to burn it ... it will just as readily melt ... "valve burning" happens when it turns red hot cos its sticking into the burning mixture when its supposed to be hitting the head and sending the heat into the head.

By definition, a warming up bike wont burn its valve ... it will hold a valve open if it was too tight when cold. But it wont start to burn till a few mins after the bike is warmed up. So weak battery or what not, no difference.

Left tendency to foul plugs - may be mixture related, maybe the petcock is sending fuel into the vacuum line. Not valve anything.

Your problem needs the 2 bores and buckets fit so they slide up and down.
It needs a valve adjustment - adjust it, it will essentially forget its past "out of adjustment" time period.

Cool.
Buddha.