So I put new pistons in my bike after doing a re-nikasil job on one of the cylinders, because the exhaust bridge cracked. There is no more than 50 miles on these new pistons and one of them is showing huge signs of wear. is this common or is there something wrong? This is the smallest bore piston and it is of course oem. there is also a bit of wear under the piston ring, not sure if it shows in the photo. any ideas lads?
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John 3:7

Was the piston supplied with the barrel when it went for plating? Is the barrel relieved around the exhaust bridge?

You shouldn't see wear like that, and certainly not with only 50 miles on them.

You may be able to dress that piston back, but impossible to say just by photos. I would seriously err on the side of caution. I would be inclined to send the barrel back to the platers with a new piston, and have the clearance checked/rectified professionally.
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Andy.
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That doesn’t look right to me either.

Andy wrote:Was the piston supplied with the barrel when it went for plating? Is the barrel relieved around the exhaust bridge?

Im not sure, i cant remember it was last year when it was done and it was the second time it was sent there. Hmm i might buy a new piston so, can sleeves be inserted into these nsr barrels because the nikasil coating seems to give trouble.
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John 3:7

Who did the plating? Frankly, sleeves are a terrible idea!
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sleeves are bad they are. hmm it thought they would be better. oh well.

I'll dig out who done the plating tomorrow

Well, first you would need to have the barrels bored (buggers up the port timing). Then you'd need to fit the sleeves. Then cut out the ports, and blend them to the NSR spec. Then you need to consider the RC Valve pockets in the exhaust outlet. Once all that's done, you need pistons with the correct dimensions and thermal dynamics.

Alloy barrels were developed because the thermal expansion of the piston and barrel can be much more easily predicted and controlled. The Nikasil plating is far superior [when done right!] to steel liners, wearing far less, and the alloy/alloy combination allows a much closer piston to bore clearance. It's lighter too.

Oh, you'd need to find someone competent enough to carry out all that work too.
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Last edited by Andy on Wed May 27, 2020 10:44 pm; edited 1 time in total

Andy wrote:Well, first you would need to have the barrels bored (buggers up the port timing). Then you'd need to fit the sleeves. Then cut out the ports, and blend them to the NSR spec. Then you need to consider the RC Valve pockets in the exhaust outlet. Once all that's done, you need pistons with the correct dimensions and thermal dynamics.

Alloy barrels were developed because the thermal expansion of the piston and barrel can be much more easily predicted and controlled. The Nikasil plating is far superior [when done right!] to steel liners, wearing far less, and the alloy/alloy combination allows a much closer piston to bore clearance. It's lighter too.

Makes perfect sense.

So do you think the only option is sending off the barrel again with a new piston? any suggestions on where to send it?
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John 3:7

All ours go to Poeton Aptec.

https://poetonaptec.co.uk/
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Andy.
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whats the rough price they charge? I also have to send it from ireland Insured

Andy wrote:All ours go to Poeton Aptec.

https://poetonaptec.co.uk/

That’s handy to know, they are right near me!

You'll need to contact them for the latest price. We had a trade price with GTPE, and I've not worked with them for 2 1/2 years now, so any reference I have will be out of date.
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Andy.
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I'll drop them an email so. The biggest killer with living in Ireland is the postage. UK companies swear we live on the other side of the World.

Andy wrote:You'll need to contact them for the latest price. We had a trade price with GTPE, and I've not worked with them for 2 1/2 years now, so any reference I have will be out of date.

Here is a quote I got from Derek @ Aptec in February this year (2020), admittedly to a UK address:

"the exhaust bridges are always relieved to allow for expansion, the bridge would otherwise expand into the cylinder and wear a flat on the piston rings.
That said it does look like this is worn to some extent.
The cost of the re-plate and hone is £137.92, return carriage £11.50 prices are plus Vat and turnaround is generally 10 working days."

Personally I would be tempted to ask Aptec if they could hone out your current plate, relieve that exhaust bridge back a tad and match to an OEM piston.

The extra postage to Ireland is worth it for those miles of green country roads and rivers of proper Guinness though eh?!?

Note: might be worth talking to them about the skimming of the head surface as well, most platers tend to do this as a matter of course, but if yours has just been done and it is square it would be a shame to loose metal (port timing and squish) for nothing.