Bugeye59 sent me these I will let him tell the story.

Did the locater pin that keeps the rings located in the correct position fall out?

Take a razor blade or sharp knife and run it around the rings top and bottom trying to cut the aluminum enough the rings will not be stuck in the piston and see if you can remove the rings from the piston.

You will need to remove the aluminum from the cylinder before you can accurately measure the cylinder, do you know how to dissolve the aluminum with muriatic acid? looking at the wear by the exhaust port you will need to bore the cylinder.

When I removed the cylinder n head, I found the vacuum hose to fuel pump at cyl spigot to be loose! This may have caused air leak and also affected the efficiency of the fuel pump resulting in the lean out.
There was also a leak at the base gasket right rear at bolt area.
If you look at the top pic, you can see where the bottom ring has migrated around to the exhaust side and nipped up on the exhaust port's,top n bottom edge.
Look at pic 1644 and you can see the bottom ring end forced up into the piston, on the exhaust side,:shock:
I will take to the piston with a knife tomorrow morn-I'm off to bed now, it's nearly 11pm here.
Tell me about the acid cleanup please.

I can't tell about the pin yet, it's all sort of mashed up together. I was worried about the same thing, want to know where it is, if it's not in the piston, then where is it? There is also several close paralell lines that run same as the rings in the cylinder walls. This must have been the bot ring as it moved around to the exhaust side.

Look close at the cylinder inside and out that area where it leaks is usually from porosity in the casting.

Hoser,when I take this to my machinist, I also want him to shave the head a bit.
Cyl is currently all new,stock, 39mm PWK carb, Rev pipe. I want a bit more power,for the race track,
but don't want to encroach into the unreliable zone. How much milling off would you go for and also final PSI Figures?
I also will be running 98 octane fuel. Honda Art or Wiseco?

Just got back from the machinist's place and he reckons that the pin dislodged,he's seen it happen before with other jobs. He has already bored it out to 1st oversize, for OEM Honda ART Piston.He said if it was'nt for the ring end damage to the ports edges that it could have been honed out as the MIC'd size was still showing orig bore size.
How much of the head should I get shaved off? for bit of extra power and retain reasonable reliability and what Comp-PSI should I be running with 98 octane? Have 39mm PWK Carb and Rev pipe. Thanks ...Baz

Took more pics this morning in the sun. You can see the damage the ring has done.

More pics, what a difference it makes with the sunlight V the torch!

Almost looks like detonation where the arrows are.

Give this to your machinist its out of the service manual its how the ports should be beveled.

pilot port bevel

Look at the colored arrows I added.

I like to add slightly more bevel in these areas so they don't scrape oil off the piston as it travels up and down.

The required piston to cylinder is .0031 don't let him add extra clearance like most builders want to add, I run .0031 on my full modified Pilot for years and never stuck a piston or had scuffing problems even when the Engine over heated.

Forgot your metric so .080mm clearance?

Page 7-5 in your manual

Thanks for all that Hoser, much appreciated! But can you answer me this please, 3rd time ive asked?
How much of the head should I get shaved off? for bit of extra power and retain reasonable reliability and what Comp-PSI should I be running with 98 octane? Have 39mm PWK Carb and Rev pipe. Thanks ...Baz

My machinist/mechanic says around 180 psi, but I thought that a bit much, if I wanted to retain reliabilty,I was thinking 170psi, what do you think? I think highly of my ol mechanic. He was drilling the Exh bridge lube holes in the pistons, before Wiseco even worked it out and noted it in their instruction sheets. Every time I see him, I think Hoser-the older model! LOL!
Do they have much trouble blowing head gaskets at that comp?-180-185psi. Thanks again...Baz

SORRY! not avoiding your question I was trying to think of the best way to answer, 3rd time is the charm tho

You don't just shave a head and go, well hacks do but I don't, head mods are kinda complicated their are many things to take into consideration while changing the design.

Here is some info on my Pilot heads, read them a few times...

http://pilotodyssey.com/duncanheadhtm.htm

http://pilotodyssey.com/Pilothead.htm

Have you CC'd your head yet to find its volume? Maybe your head was already machined in the past, only way to tell is to check the heads current volume, I found 49cc to be a pretty good volume, you also need to check the squish clearance to ensure the piston is not too close to the head, I am dealing with this right now with finallygot1'a head, I removed the damaged area of the head by machining, now the squish is going to be too wide so I have to machine material off the gasket surfaces to tighten the squish, this adjust the volume of the head (cc's) so I have to CC the head and if the volume decreases too much I have to remove material out of the dome area to increase the volume again, I cant make the final adjustments until I have the Engine assembled to verify the squish clearances.

So his head is still here until the bottom end is done....



Give those pages a read let me know if you still have questions...

Go here and read as much of these as you can http://pilotodyssey.com/Fuel-Squish-Detonation.htm

Running again?

No, not yet.Still waiting for parts to arrive.Hopefully today.

Well, finally got all my parts for top end rebuild,1st oversize Honda ART 25, did'nt end up shaving head,erred on the side of RELIABILTY. Got stuck into it, and before I knew it was nearly finished.
When it came time to install the reed cage valves, I checked it against the sun for wear n holes-gaps. Did'nt like what I saw,lots of pin holes,black carbon fibre I think, but had nothing else to install, so put them in to find out PSI. See pics.Judging by the diff colours,gold,silver,black,there's a lot of abrasion happening there due to inadequate air filtration.
Very dissapointed with Comp reading-125psi! Must be all the pin holes in the petals? I remember a while back there being alternatives to Pilot petals, CR250? Year? Those I can get here in Aus, but Pilot ones,forget it!-another 2 weeks! Recomendations??? Next race, this coming Sun.

Are those actual holes in the reeds or just light showing through the resin?

If your replacing the whole cage go Honda or FMF

You know how to check the squish clearance?

Check compression again with another tester if its 125 and the cylinder is stock something is wrong! don't even start the Engine!

Give me details on exactly how your testing compression and detail pics of your tester, does the tester have the valve core at the end where it screws into the head?

Well? Tap tap tap.

Sooooorrrrryyy!
I got that pised off with it, that I have DIVORCED it for a while. Major dummy spit! Spurlatt!!
I decided to get back to it when I clear my head!
Ive, instead, been fiddling and tinkering with my other Pilot.ssshh! Hoping that the first one will get jealous and respond better later.
The head is near new and totally stock. So was the Cyl, until my Mechanic, ol Dean cleaned up the ports, and inlet areas
Comp test done with wide open throttle till highest reading is obtained. Valve release is at gauge end.
I had already started the Engine, just in the back shed, for peace of mind.Just for a few mins, seamed to run fine.

Update?

Running?

A ok?

Still have'nt touched it Hoser. Been working on my other Pilot getting it ready for racing at Northam Speedway.
Trouble is, a lot of the other guys have sold their buggies or can't make the race(excuses)so don't know what's gonna happen with our superlite class.It's on this Sunday and so far only 2 buggies-me included-have nominated.I'm hoping like mad that more nominate in time to keep this Good Thing going! I am addicted to the rush of racing now and need a regular FIX!! The Promoter was also talking about local TV coverage and $$$Prizemoney I wish you guy's were closer to Aus...or maybe I need to move to your Imperial,LHS Steering wheel and Roadside Driving Country, to get my fixes.

WOW I can see why your depressed you need to do something to rally your brother racers.