Know we can look at the other vertical scuffing marks of the cylinder walls as they tell a great story. By the way hats off the machinist on your cylinder.

The Wiseco or stock piston (Arts) for that matter when which would have failed sooner form this event. Shows a great story line all the way trough failure on most parts of the Engine as and there relation ship to heat dissipation for combustion. The pictures does show signs of cylinder scuffing. We must look at this very carefully to make determine from what we see.

As a general reference scuffing one item against another. The visual is material one to another. Now why or what ?
In our case we pretty darn sure the what, is Aluminum to Steel transfer. The why is much greater item to distinguish.
For this we conclude one,two or three things or all three items in succession.

#1 lack of distance from materials
#2 lack of lubricant to act as a barrier between the two metals
#3 The expansion rate of the two metals for heat.

We know the original static distance was ok. We know the amount and quality of lubricant was ok. What we don't know was the rate of expansion for the two metals. We can however conclude the rate at some point was not acceptable due the fact there was scuffing.

For this we look at the cylinder and the piston to tell the story. For me the key is the scuffing lines on the cylinder.

This tells me the piston crown has seen excessive heat which was absorbed down the piston into the boss area. wen this happens due to the shear mass of that area it swells outward with less flex like a the skirt of the piston. The amount of this scuff also tells me the event was quick. If the event would have taken a longer period of time the scuffing would have been greater as well as the piston crowns edge would have started to let go.

If you look at the exhaust side pic I highlighted a area that can be referenced back to piston crown pic and offer as evidence of that statement. The area above that is shinny, above this high lighted area can be measured and turned into a degrees of timing.

I must go for know so thank you for allowing me to comment.
Adnoh

If I may be so bold as to suggest you run the stock pipe and higher octane fuel.
Amen.

Plug is a BR7ES

Plug Pics - Whole and chopped (Disclaimer - Plug was definitely gapped appropriately - not as pictured!)

Whole





Chopped





Paul Turner Pipe and stock silencer - confirmed

"I would also like to confirm CR not static compression. You can simply get me the number either in English (Being humorous)or mm. Take your caliper and set it on the base (tail) on top of the cylinder and run the tail down until it reaches the top of the exhaust port. please provide this number. I can enter into my data spread sheet. I used my data for your Engine set up using known numbers and it came out ok so I need this to confirm."

Here i have a question and please forgive my lack of knowledge - CR - What does this refer to?
Next, I do not have a caliper to take these measurements but if this is definitely necessary, I will get it done.
Six pics per post - moving on.

Pics of Piston

Piston Bottom




Piston Sides






Let me know if there is a detail needed that is missed in these due to angle

Cylinder walls actually look pretty good after looking at the piston sides.





Again, if there is any detail needed, let me know and I can take additional pics.

Thanks to all,

Dave

Damn that piston was still useable if it weren't for that hole. Even could of re-used the rings possibly.
CR is compression ratio.
Check your mail.

OK - Just checked out this page.
http://www.pilotodyssey.com/uccr.htm

Correct me I'm wrong here but i will not be able to calculate CR since i have already removed the cylinder?

You won't but adonh will be able to calc for you...

I think we have all heard the statement: "Money talks, bullshit walks". Well I live by it.
So I am going to make you an offer you can't refuse. If you decide to accept here are the rules.
1) Put new piston and rings in and pass the pressure test.
2) You will run straight AVGAS/oil mix only. You decide your mix ratio and fav oil brand.
3) You can run which ever pipe and carb you want. Stock jetting in the carb.
4) Fuel pump passes flow rate.
5) If you run two full tanks of AVGAS and don't pop a piston I win. If you pop a piston you win (sort of).

I will send you $400usa toward another rebuild if you pop a piston. If it lives I owe you nothing.

Everyone on this site has now read this.
I am good for the money as you can ask members here who I have had any dealings with.

Adnoh will be able to figure it out for you if you get him all of the specs he needs but riding season is almost here so it is time to stop stroking and grab it by the balls. In the end I bet my money Adnoh will come to the same conclusion I did -- "Detonation".
Your local fuel supplier has poo fuel. May be it's the same scenario that happened here in Canada. Some "NEW CANADIAN" who owned a gas station was scamming customers. There was regular fuel in the premium tank. I may be reaching here.

Do we have a bet ??

I wouldn't take that bet, and that's no offense to C.O..
1. 400 wouldn't cover a bottom end/a hole in the case (s) etc.
2.Working on the machines is fun and this of is of course as noted by dipnadactyl is only so when not wrenching on the same item each time. I don't think he wants to take a chance at doing this top end again in a day or two.
I agree riding season is here but wasn't dipnadactyl ready to sell it when she let go this last time secondary to fustration?
3. AV/race fuel isn't cheap.
4. AV/race fuel can be an a@@ ache to obtain...
5. This is worth a quick read too...http://www.autofuelstc.com.. AV gas might not solve the issue depending where you are located..
Regards G.O.

No bet, sir. G.O. makes very valid points regarding frustration and money. I have too much of one and not enough of the other.

May I ask if your gas tank is nice and clean or is there lots of rust? I have seen where an old rusty gas tank kept flaking off small pieces of rust and clogged the fuel filter and the main jet of the carb.

The carb can be brand new and super clean, but any little piece of rust can clog the main jet.

Original tank was replaced with a super clean tank - feel pretty confident the tank has no rust. Will be draining and disposing of almost full contents currently in it (thanks CO ).
Will give a good inspection once drained just to make sure.

Good morning,
I have been collecting information on you continuing issues. Thank you for taking the time to take pics and posting them for all to view and consider possible causes.

During my read and collection I ask for some more pics.
#1 the inside of the pipe where is was welded up.
#2 the #3 piston under side, mainly the exhaust skirt area.

Also please confirm that you have corrected the coolant line issue and that the factory fuel pump has been replaced

I do have additional comments as well. I do not like the fact you have had sort cycling issues and this may be leading to your failures. The way your piston looks all scuffed up is simple loose of lubrication form the intake charge being cooked off and then it all down hill form there. At some point there was some ring flutter as well. I find this a little strange due to the rings being Wiseco. However this may be from when it went into pre ignition and the CDI (Capacitor Discharge Ignition) had no effect on stopping it.

Be sure to check the filter too.
Here is a link that Hoser comments about cleaning the filter, this will help you see what comes out of the filter to see if there is something suspect about it.
viewtopic.php?f=2&t=13183&hilit=Fuel+filter

Ok. I just wanted to throw it out there because I wanted you to know that anything coming out of my yap is the truth as I believe it and have the experiences in the past to back it up.
I will back up my yap yap with $$$.
I stand by my previous statements about the fuel.

Thanks Pilot Bird - will check it out.



Inside & Outside of pipe, welded area -




Piston Underside (think this is what you are asking for but please let me know if not and can edit response)




Carburetor coolant line was plugged on both ends - at radiator and cylinder head. Other than a one time issue with the radiator getting clogged with grass and weeds from driving though the thick stuff, no overheating problems. On that one occasion, i immediately shut down and let cool before driving back to trailer. Once home, radiator was removed, flushed, fins cleaned and blown out with compressed air and refilled with new coolant. Also confirmed that coolant was moving when Engine was running.
Fuel pump is what came on the tank I purchased - does not look like the stock one that was on the old tank but was tested and flow was up to spec - almost 5 oz. in 10 sec.

That is a mikuni hi flow fuel pump, I run them on all my pilots. They work great:)

Thank you for the additional pics.
You know if some one offers a paid in full guarantee why not? sure was nice of him.

Any way. As I said I read though and noticed you said you had the pipe welded and as the picture confirms there is reason for concern. There are many places that can be a hot spot and start a back flash or the stuffing charge. see pic.
If you go and look at the way a two stroke Engine operates the intake charge is rammed down the pipe through the exhaust port and then the pressure wave of the pipe shoves it back in to the cylinder before the port is closed off by the piston movement upward. see this animation http://www.pilotodyssey.com/tech.htm

If this charge cooks off then the combustion strength is now lower and the mixture leaner. This could be why it all of a sudden spikes. I was originally thinking head gasket however pipe is a concern. no matter what one should clean it up as a save guard

Also I ask for pictures of the #3 piston prior one, due to what I saw on #4, see pic.
basically that should not be there and coincides with first statement on top of piston pic. If there on previous piston than one needs to find out why. You should not have carbon tract like that on the piston. see pic.

Please get second options on every thing I say as I'm just a back yard hacker and not a professional Engine builder.
Just trying to point out things that do not look right from my past experiences.

Now take you piston and side it back in the cylinder and turn it up side down. Line up the rings locking pi with the mark on cylinder. Now take a sharpie with the piton at a TDC (Top Dead Center) position and mark up the cylinder using the piston skirt as a guide and then remove the piston and take a pic.

here is a couple of pics to what I mean. I do this to set porting limits at varying port timing stages. Ths will also help with why I see what I see.

here is a pdf of what I am compiling so far.
lot yet to do.
Thank you for sharing

Adnoh, Thanks for the time and effort you're putting in to this. It is appreciated. I will get measurements on cylinder asap. Have to run out for work so maybe a few days.

Adding a couple more pics with some items to note - see the top edges of the cylinder walls and the differences between the intake and exhaust sides.




Looks eaten up on the exhaust side.

Reread your request for piston pics and now understand what you were asking - here they are. You'll see the dark marking on #4 is not present on either of the two previous but those two melted rings vs. #4 popping a hole.

Piston #2, #3 & #4



Piston #4, #3,& #2



#2


#3


#4