Holy Cylinder Block!

[Drewski]

'Just collected a few bits from the vapour blasters, check out the cylinder block.....anyone seen anything like this before? What's caused it? I don't recall spotting any of these holes before it was blasted, (will try and find a pic), although the bottom surface was still covered in gasket.

[Alan H]

The softer brass SRIS connectors look ok, so it may have been there before the blasting.
Do you have a 'before' pic to compare?

[oldjapanesebikes]

That looks nasty You do often see a bit of pitting as the alloys used often were 'not the best'. As per Alan - a before photo would be useful.

[Drewski]

I can only find this photo of the block before it was blasted. The rad had a leak and the head gasket was "dribbling" front & centre. There were pink splash marks everywhere from the coolant. I wonder what type of coolant it was? And if it's caused the damage

[Drewski]

More pics:-



Check out the state of the centre pipe, where the leaks were spouting over:-


...and where the paint has come off the frame:-

[Drewski]

If it is the coolant, I'm guessing my Rad will be scrap too then?

[oldjapanesebikes]

If it is the coolant, I'm guessing my Rad will be scrap too then?

Sad so say, but likely. I also take a close look at the impeller on your pump and anywhere the fluid would change direction - the lower hose connection and thermostat housing for example.

[Drewski]

The coolant galleries actually don't look too bad....there's no sign of the "rotting" visible around the centre exhaust for eg. Could the coolant have been reacting with something else to cause the damage? Gasket material? Steel and alloy together? Some kind of sealant? The atmosphere? Strange how the top of the crankcase didn't get as bad even though the coolant that had leaked would have "pooled" on there. I've seen this sort of damage casued by poor earthing, I forget what the process is called now but you can also get the same effect on head race bearings.

[akendall1966]

Oxygen - once oxygen in coolant and trapped gas is consumed corrosion will slow or cease. In open air where oxygen is in free supply it will continue as long a conditions for corrosion to occur persist.

I had a Villiers engine that disassembled sitting in a plastic buckin a damp cellar where it would collect condensation. Alloy surfaces touching the bottom were sat in liquid and corroded and once cleaned up were pitted like yours. Time and the right conditions and alloy gets eaten away.

[tz375]

If you have a spare cylinder, that would probably be the easiest way to go but all is not lost. Worst case scenario, you can skim a mm or more off the lower face and fit a spacer plate.

If you want to raise the barrels, machine the appropriate amount of the top face to correct compression and if not, use a thin spacer plus extra gasket.

[Drewski]

I did think about a spacer plate, I could use the one made to lift the earlier barrels. I thought the mess at the front would look too rough but I guess most of it's hidden under the exhaust flange.
I also have another potential problem with this block.....both the left and the centre sleeves are way off centre and are both worryingly thin at one point after the rebore, (2nd over).





Am I actually looking at the thickness of the sleeve......or is part of it embedded into the casting?

[rngdng]

I don't know but whoever bored that could have corrected the problem instead of just going along. I would get another cylinder bank.


Lane

[tz375]

Liners are always off center - maybe not always but all the barrels I have seen are like that to some extent. I suspect that it's an issue with how they located the cast in liners in the molds. That barrel happens to be worse than most.

You could bore it out and see if it's OK or you could get new liners fitted. Or replace the block. The latter, as Lane suggested, would probably be cheapest and cause least worries.

[Mencie]

Sad to say I had very similar on a pair of GT500 crank cases a few years back.

Before they went to the blasters, they had a lot (and I do mean lot) of heavy oxidisation, like the bike had been parked outside near the sea somewhere.

The cases came back like yours and the guy explained that the oxidisation eats into the alloy but is softer than the metal itself so when blasted, the softer oxidised material is cleared back to base metal, whatever is left of it that is.

My top case was so thin in places I junked it and got another from a breaker.

[Suzukidave]

It sure looks like whom ever bored your cylinders screwed them up bad , Like Richard commented i have seen plenty of cylinders not lined up with the gasket or head but he should have centered the bore instead of going so off ... in my opinion