Right my new camera arrived today Wahoo, so whats the first thing i do??? take some pics of my dead piston!! the one that was done at oulton!!!! not the one from the other day

i was amazed at the damage that can be done from a dropped ring, if you look carefully on the crown youll see a bit of ring stuck in it and as for the chunks missing from the side???? and the big grove down the other side im afraid i never got a shot of the barrel!!!!

http://www.bikepics.com/pictures/630549/
http://www.bikepics.com/pictures/630548/
http://www.bikepics.com/pictures/630550/
http://www.bikepics.com/pictures/630552/
http://www.bikepics.com/pictures/630553/

is the barrel that broke the other night the same as the barrel that this piston came from???

I haven't seen the latest piston barrel, this was done at oulton a few weeks ago, but its the same barrle and piston thats gone again this time, which makes me think fontyy is right and its probbaly a bit of ring stuck up the top, ill get pics of that when i can!!!

That is proper forked innit? Good effort mate!
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

i had the same problem but spotted it the first time,your piston rings are catching the power valve,i would put money on it that at some time when it was replated (i dont know what the bit is called but i will try and explain it to you )the olive/sleeve/collar that the end of the power valve shaft locates into which is deep in the barrel came out, this allowes the power valve to move and the rings catch it .this happened to mine 1000km after a re-plate
so it can happen at any time,the result was a piston that looks just like yours and a knackered barrel.Andy now has the barrel if you want a picture but you will need to removed the power valve shaft and look down the hole to see if it is down there or missing,you can do it with the barrrels on,if you want to know more i will pm you my number.

Wayne, Thanks for your time good to chat with you, here is a pic of the good (well bottom) piston from my bike, is this the sort of mark you are talking about???? if the power valuve has got the bush missing then your right it may have caused another ring break!!!!! if you could post the link up and part number ill chat with sam and make sure mine are still there or make sure some are ordered and put back in.

http://www.bikepics.com/pictures/630601/

Right I cant paste the page from the parts manual or e mail it to you as it wont let me also the part I think your missing isn't shown in any pictures of the exhaust valves or the barrels go in to the parts manual and go on the the link for the 21 and click on exhaust vavles and on cylinder head,the part does not show up.You could ask Andy if he has one or if Stephenrc45 has one.

You only just got away with the lower one too!

You can't really tell what's happened just by photo's, but that motor definitely needs some careful measuring up. That damage could be a combination of clearance and compression.

Can you post pictures of both combustion chambers please.

Er, just so you know... I can take payment via credit card through PayPal for engine work! (Sorry! )
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Andy.
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Andy,I think its the samething that happened to mine when the collar got left out from were the power valve goes in the barrel as the piston looks the same and I bet the barrel looks the same as the one I gave you the other night.

No pics of the barrels im afraid. This was the first sieze Andy and i did have squish and compression problems, but they have matched the heads re honed the bottom barrle, replated the top and new pistons and rings.

This time its gone pop and i dont know whats caused it yet, Wayne thinks its may be a coller/bush that sits inside the barrel is missing, I can only see a bush part on the ns250rg and mc18 parts manuel, Do you have a part number for the 21?

Or like fontyy said in a previous post it could be another bit of ring that hasnt been flushed out properly???

gota bear in mind that the pics posted are the pistons that have been in the bike for good knows hows long, You did the crank did you change any rings/pistons etc, the only other engine work in this area was the head conversion which i fitted the wrong head, but that was the frnt barrel not the top!!! which is causing the problems!

What else could cause the marks on the piston? bad powervalue set up, worn bushes?

That mark on the 'good' piston definitely looks like powervalve. The gap between the two scrapes co-incides with the exhaust bridge.

Hope Sam is understanding!
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

anybody got a part number for the mc21 powervalue coller wayne has been talking about? might be worth getting some just incase. what else would cause the power valves to hit the piston?

Boring the barrel out?

Being a Suzuki?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Thanks Dave!

MAtt, Andy if you chaps have seen this coller thing, i would be very greatfull if you chip in with a pic or partnumber. Clutching at straws maybe but something has made the bike go pop so quickly, An old bit of ring maybe but there is clearly a powervolve issue as well!

Here s another, Has anybody modified the powervalve itsself so that it dosnt hit the piston/ring or would this be a bad idea?

It's impossible for the piston to hit the RC Valve, by way of it's design if assembled correctly. Even with the Valve assembled incorrectly, the probability of it happening is still so minute, that I don't think it is a viable explanation. I don't think that is your issue.

40:1 is clearly WRONG. Matt has the only valid point in this thread so far I'm afraid... what does BDK know that HRC doesn't?

I think that your problem (withoput actually having the motor in front of me to measure up) is most likely a combination of high compression and bad lubrication. It was only a matter of time before one caused a failure in my opinion.

Sorry if that's not what you wanted to hear.
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Andy.
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