Ok so I got the pistons off. Rings on front cylinder were outside spec. Rear cylinder rings were borderline. The pistons have stains on the sides where the combustion would have blown by. All in all the cylinders look fine, but very dirty. I have to buy a rebuild kit, a local auction site has one up for $300 NZ = 117 GBP. No cylinders included! Is this a good deal? Andy - do you know why my front cylinder head would be rough as I described, and does it need to be replaced/machined?
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'87 MC16

Regarding Price...

Pistons X 2 - $199.80
Piston Ring X 2 - $103.00
Clips X 4 - $3.60
Cylinder Gasket X 2 - $15.20

For $320.60 (AUD)

So that works out to about $340 NZ. So your getting a better price that me. But I had to pay for shipping from japan as well

Didn't see it was an MC16, disregard my rambling.
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Last edited by fontyyy on Mon Dec 26, 2005 2:39 pm; edited 1 time in total

Wait on guys, the TYGA representative selling the kit says MC16 cylinders aren't produced anymore, so they aren't included! So for around $300 I get:

2x Gasket, Cylinder
2x MC16 Gasket, Head
2x MC16 Piston Ring
2x Piston Bearing
4x Piston Circlip 15mm
2x Piston Pin

But to be honest, the things I need most would probably be the cylinders and rings - the bearings and wrist pins are fine... Is it OK to reuse the pistons as they are?
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'87 MC16

Does the head look like this?




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Andy.
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Yes, it looks very similar to that, I can feel some bad news coming on...
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'87 MC16

The pitting is quite a bit more severe in my case.
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'87 MC16

So what's the diagnosis I'm confused now because from looking at the parts manual, the damaged head seems to be from a different model (looks like MC18) - there's something fishy going on here so not even sure yet how much of the bike is original. Could be up sh*t creek because who makes cylinder heads (let alone cylinders) for an 18 yr old bike? Unless I start to get really creative...kiwi ingenuity can only go so far
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'87 MC16

That head is a stock front MC21SE one. It had covered around 10,000 miles. The markings are detonation.

It could be used again, but any worse than this and it would need machining.
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Ok, so mine will probably have to be machined - is it ok to just remove material until it is smooth, or is combustion more sensitive to the dimensions of the head? I'll just post some pics today if I can.
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'87 MC16

You need to maintain the shape and the volume of the combustion chamber, or you will lose compression.
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Andy.
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Check out pictures here: http://pg.photos.yahoo.com/ph/ahug030/album?.dir=1b00

As you can see from the last picture, one of the heads is in bad shape (compared to first picture), also the cylinder has some minor surface 'rat bites' on it that don't come out too well in the photo. The barrel of the offending head has a small gash on its mating surface - could this have caused the erosion of the head? I need to figure out what caused the problem before I go out and spend $$ on a new part that may be damaged in the same way.

The eroded head looks like it is from a different model by looking at the parts manual (the top head in the fourth picture across), maybe there is a difference in dimensions that could have been significant...

Thanks for any help guys.
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'87 MC16

That looks like mechanical damage, broken ring or something bouncing around ?
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The head looks in very bad shape, but the piston doesn't, so that would suggest to me that the damage on the head was from a previous disaster. It looks as if the ring broke then did the dance around the conbustion chamber. It's not normal detonation.

I haven't done a huge amount of MC16 work (practically none actually), but I have offered up MC28 pistons and cylinders and it looks as if they'll fit without any trouble at all.

I can't say the cylinder will be all that much better because what I was dealing with was just an MC16 bottom end, but the 28 piston's a better choice because of it's crown coating, compared to the MC16 that's just plain aluminium.

There'd obviously be a few plumbing issues by fitting later model top ends, but I doubt that it'd be a major headache if you were willing to do a little research to find hoses and stuff.

Thanks alot for the advice guys, I did suspect that the head may have been reused or swapped out from another bike...the last owner has proven to be pretty reckless/ignorant in this regard. But thats good news really, as I can get a replacement '16 head and reuse the cylinders+pistons without too much worry, although it sounds as if MC18 cylinders might work out if I can find a pair...
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'87 MC16