Hello everyone,

Please attached pictures of my MC21 barrel. There is a small amount of "pitting" on the mating surface and I just want to know
if it's ok to put back together like this, or will it be a problem?

Could I get away with putting some sealant under the gasket or does it need to be filled properly and rubbed down?


Thanks in advance...

Al.
_________________
Cheers....

Al

Bikes:
GPZ900
NC30
NSR250SE
RGV250 vj22

That looks pretty deep, though its hard to tell from photos.

You could try some extra sealant in there, but make sure it's just a light smear or the head won't seal and you'll end up pressurizing the water system and spraying the bike in coolant!

Do NOT be tempted to just torque the nuts down, its pretty easy to strip the threads in the barrel, or crack the casting completely.

Did my photos get removed?

Or did I do something wrong?
_________________
Cheers....

Al

Bikes:
GPZ900
NC30
NSR250SE
RGV250 vj22

Oh, they're back.

What the diddly?
_________________
Cheers....

Al

Bikes:
GPZ900
NC30
NSR250SE
RGV250 vj22

You would be better off lapping the barrel on a sheet of glass, and using a 0.6mm HRC base gasket, or possibly filling the eroded areas with some JB Weld and flattening it back.

Using sealant on the head gasket isn't a good idea in my opinion.
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Andy.
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Has that bike been used with plain water and no anti freeze ?

Andy - we would all benefit if you explain why we should never use sealant . Thanks .

Now that I don't know, I only recently acquired it, but it did have coolant in it when I stripped it. I suspect it may have been caused when it was re-plated as I don't remember it being like that prior. But I can't be sure.
_________________
Cheers....

Al

Bikes:
GPZ900
NC30
NSR250SE
RGV250 vj22

Neal wrote:Has that bike been used with plain water and no anti freeze ?

Andy - we would all benefit if you explain why we should never use sealant . Thanks .

I never use sealant on my head gaskets.

I don't think it's a case of "shouldn't". It's more like if you have to then there's something wrong. If the mating faces are flat and not pitted, and the gasket is in good condition then it will seal.

Matt@TYGA wrote:
I don't think it's a case of "shouldn't". It's more like if you have to then there's something wrong.

Therefore, you shouldn't ever use sealant!
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Andy.
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What I'm trying to say is that if I/you were just about to line up on the grid OR it was "Happy Hour" at the Buffalo Bar THEN the absolute minimum of sealant on the mating faces is not gonna cause a problem.

Just don't expect it to fill any major gaps and stay there when the pressure is up, and do expect to fix the problem of why it needed sealant.

Also, some sealants are not coolant resistant. I believe nasty Threebond 1104 is. Well it must be as half the two strokes in Thailand have it dripping out of the engine.

OK, I'll give you happy hour at the Buffalo, but other than that...
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Andy.
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And that's why honda put the black "rubber stuff" on the gasket to seal the two faces . If it can't seal them , then the 2 faces are not mating properly .
I use a light smear of grease on the gaskets to stop them from sticking . It may be rough workmanship but it helps me .

If the black coating on the OEM head gasket isn't enough to seal the head to the barrel, then there's something wrong, period! That viton coating is exceptionally thin (approx 0.025mm) and does promote sealing, but also ensures the minimum of expansion (and also movement) between the mating surfaces.

Its thickness also means it's easily damaged, and therefore shows where leaks have occurred, or are beginning to become a potential problem. This should be warning enough to prevent erosion around the stud holes if the top-end is properly maintained. Clearly Al's wasn't!

Silicone sealant takes 30~60 minutes to "set up", and once (an old 80's 4-stroke motor!) assembled, shouldn't be run for 24 hours to allow it to cure completely. Something many people don't know.

You also have no control over the thickness of sealant, and it's unlikely you will ever reproduce two identical builds. Not exactly good for a high performance engine! It was designed for mass production car engines and cost-cutting.

Using a very light smear of grease on a base gasket is acceptable on a road bike, but unnecessary on a race bike, as it should be apart long before the gasket has time to bond to the cases.
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Andy.
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