Looks like you were having fun for sure. I would not worry much about it. Clean it up put it back together, rejet and run the piss out of it. Just keep a closer eye on the plug. sputter on top after it not being there is fuel mix getting richer. why who knows, jetting, Engine going away, dirty air filter, air and temp changes. main thing is you had fun. Be sure to pressure test upon completing your rebuild. Probably should have tested before tare down though.If you put the old pipe back on your jetting should be close as it was jetted to that from the start.

It did sound to me like it was hurt. Heck I've ran them until the piston exploded so rock on.

I would look into replacing the case studs and using a locking agent on the ends that go into case and use new nuts. One reason they can come out is the thread stretch on the nut end from torgue or not having good fit in case. I would also recommend new hardware for the head as well an give the head a good once over for flatness etc. If you find any issue with head, remove head studs and clean up the deck on the cylinder. You run ave gas so no big deal. New o-rings, new clutch side seal, new case studs and nuts, (check all head studs and nuts) decked cylinder (top) and check head for flatness. This will help you have a successful top end rebuild.

You can do all the clean up and decking your self with care and good flat surface and sand paper. I use a old flat top of a scroll saw table and stick on sand paper. Oil it up and use circle motion with straight down pressure. I have two set up one with 120 and one with 400. The book gives you a good idea on how to check for flatness. However even though it checked out a good cleaning with help. remove the head studs with the proper tool. It is a socket that slides over the stud and locks on the smooth part as you turn it. If you see signs of locking compound just heat up the stud a little and break the bond before removing as not to damage threads then run chaser through. The chaser can be an old stud or bolt with slots cut in the threads. Not a tap but a chaser. Check you stud hole depths and after you reinstall check all studs heights from deck. Slide on our head dry and check nut thread height in case you need a washer or spacer.
A tap can and will damage the threads.

Don't forget to get ride of the carbon on the exhaust flange. before you install pipe also make sure with piston at TDC (Top Dead Center) the piston skirt closes off the exhaust port completely. if you see it don't run a feller gauge in there and let me know.

Take your time and have fun and thanks for sharing with the board.

Forgot,considering what CO said. Take a pic of the bottom side of the piston and post.This will help with the discussion. A pic is worth a thousand words. If I did not mention it the sharp edge on the ring is not good. Post up your ring gaps, and clearance numbers before you put together. I will run the numbers.

Food for thought: after you run it a while you can easily just pull the jug off with out breaking the head seal. then you can check your rings, piston condition and bore easy and cheap. Then new base and slide right back on, pressure check and Cruz on. yea I thew Cruz a shout out.

pics of head stud tool

Pulled some pics for discussion that is relevant.

#1: Exhaust flange of an over rich slimier to yours not a big deal.
#2-4: The piston that was remove for checking. Ran good at this point even in this state. However not for much longer.

Piston 1-1: you can see where is has some swell seizure marks and heat load on piston, skirt, pin with a over rich mixture on crown with no major signs of over heating of the crown. Looking at the top one would think all is good.

Piston 1-2:You can see the heat load ( brown spots= heat load) on crown and skirt other wise looks very good. No combustion gases no signs of over loading other than brown spot on skirt. The brown spot on roof is the plug location with a stock head and the amount of carbon build up with the use of a milled head and hot plug (normal). The brown spot on skirt not good Got on the gas to quick before reaching roper cylinder and piston temp. My Bad.

These brown spots are formed form intake mixture bonding to the piston form a hot spot on the piston or tel tell.

More but trying to keep simple.

Piston 1-3: Look close at the relation of piston areas. The areas above and below the ring lands and the camp and barrel taper locations. Look at the color above and below the top ring. the color between the top and bottom ring and below the bottom ring. You will also notice the the combustion marking (brown)in certain location below first ring. this is from intake charge at port and heat load in that region. (OUCH)

Now you see what i am talking about when it comes to ring flutter and gas pressures between the rings and there effect. You can also see the effect of the thermal load on the piston in a given area or region of the piston. You can also see the effects of the load shedding thru the rings from the piston aka color of the piston in a given region. the crown color to first ring and then second then skirt. You can see the top ring is shedding the majority of the load to the cylinder. As we move down the skirt the heat load form (cold)seizure is not related to the upper section of the piston rather expansion rate. This is confirmed from the bottom of the piston.

Very seldom do we have an opportunity to see this before all hell breaks loose and we chase our tails. However for me it not a big deal to inspect an Engine after a hard ride. after all it still ran like a bat of of hell. Not for long though as the top ring would start to go away and then the second and then look ugly.

Adnoh

Note: In Piston 1-2, look real close at the relation ship of the pin boss area and the pin its self in piston 1-1 pic.

You can see how the heat load has an impact via brown spots. Again my fault and not good cold sizures. to much laod too soon =on the gas to soon. Wiesco baby

Thanks for advice
Pics of piston As requested.
Took cylinder and pipe to work today, cleaned up the exhaust flange and inside of pipe.I do jewelry repair so I have proper tools for Doing port work(if I knew what I was doing lol) But I felt comfortable enough just to take care of the edge that was sharp on that one port.
Since Hoser Has disappeared who can do my bore for me? I contacted methodical fabricator three or four days ago do you see if he was available if I needed him and he said he could do it.I told him OK thank you, I wanted to try a local first.A guy I met on Facebook who I’ve met up with three or four times for rides told me he knew a couple people local who could do it that he has had work done. I really wanted to go that route,#1 You don’t have to worry about your cylinder getting busted or lost during shipping process,You don’t have to pay for shipping both ways, and hopefully you can develop a relationship and trust with somebody local.So when I contacted my buddy about who to do the work he said if I were you I would just get methodical to do it, the shops locally don’t know as much as he does about these engines so there goes that ideal
So I recontacted methodical yesterday morning, asked him if he could still do it, and gave him the link to this thread to see if he wanted lend his expertise, but I have not heard back from him.So if methodical is out is there anyone else?

That piston looks good to me.
Might have to rethink that lean out but I still lean that way.
You have scarf marks all around that piston so that also tells me it was warm and had grown a bit.
Pressure test and pump flow when it's together. Post if any blown seals or faulty pump.

Man would I ever like to re-weld that thing and stuff it into an Engine with a homemade head .

I vote for Meth as well.
He don't show up much anymore and rarely comments ------- like many others.
CO

I havent pressure tested Engine in years,seems like I made a kit for the ody to do it but never for the pilot,what do I need to get for pilot to do it? And when you say pump flow,are you talking about testing fuel pump? Never did that before either

Oh Christ ur ded.
Same pressure kit.
Yes fuel.

Call around local machine shops. Look for one who knows big bore 2 strokes. You’ll find one I’m sure. Do you cave any way to measure the width of the exhaust port? What is the actual bore width? Your exhaust port may have been too wide, and when the piston/ring gap clearances fall out of spec the damage can happen

Thanks for the pics. How about one of the piston pin.
Now that I have seen the piston type a lot of what I see makes since. Thanks
Since your going to massage the port your self study up on chord width and how taper the port for the ring. I think it good your going to give it a shot. Go slow and do some of the work poor to hone. Then you can smooth out the edges afterwards. Again the book has a good pic on champfer.
If you would be so kind as you put it together get me some pics. At different stages of build. I will get you a list. You can do a practice build with out gasket for pics. Then do final assembly.

My area of interest it piston position and port open and close relationship to piston position.
One thought I have is the primary compression ratio to secondary. May answer a question or two. Would also explain what I heard in the video. Zero and others look at his piston and look at his standard pilot cylinder and see what you think. I bet CO gets it.

Hoser did original rebuild,I would think he would have said something? I currently don't have a way to measure port at home,my digital calipers broke,I need to stop by Harbor Freight and get another pair.
Heres thread
viewtopic.php?f=1&t=15147

That's not nice CO
I'll have to see if i can find kit,I thought the one I made was made to fit ody intake,I'll have to find it and see.don't know if I'll get to it today,got a shit ton of stuff to do today in prep for taking travel trailer n boat on vacation and finishing up sprinkler system I installed at mom's house

Piston pin

You may have misinterpreted that comment.
I will try again.
Oh Christ ur ded ------- (Blown engines) (If you don't regularly pressure check and flow test)

Looking at all those pics again.
You got a stock jug there that has been hogged out. When you do that the holes get bigger don't they ?? That changes timing a bit -- NO ??
You also got a big arse exhaust hole there (don't misinterpret) , putting you at the edge of a snagging ring.
Now you put on a different pipe after it has run well for years . This changes things NO ??
We all know that we can change our two stroke performance by changing a pipe.
That pipe might have caused fresh charge flow problems.

So I ask: Could this have caused a bit of ring flutter and snagged a ring in that exhaust port ??
After all you didn't re-jet (I think). It may have needed a bit more air now because of that pipe and that's why it ran better with the lid off.
I'm confused now but will hold on to my old theory until a pressure check verifies seal condition or a poo fuel pump.

Before I changed the pipe, and had the old pipe on, I would still have to adjust the airbox accordingly by taking the lid off and on so nothing change there, so when I had to do it at the dunes that was no surprise.I knew changing the pipe sometimes requires jetting accordingly but after changing pipe it seemed like there was no change and didn’t require a rejet.No I didn’t do plug chops and most likely I never will,I know that’s a big no-no in the two-stroke world but I have no place to do it and I’m not suddenly going to have a place to do it. The ATV parts I go to do not have good straightaways for me to do it, they are made for mudding. I’ve Tried it before at the beach, but conditions have to be perfect. Unless it’s the winter much the beach is always too crowded,I’ve tried doing plug chops there before and wind was blowing hard I was afraid sand would get in Engine when I pulled plug out.

As far as fuel pump,I’ve tried searching for it on here and on YouTube and not finding conclusive answers, can you explain to me how I should do it on my pilot?
Edit: I did find fuel flow rate for pilot is 4.7 ounces for 10 seconds at idle.
Also another thing just hit me,while researching the pump test I found out that 89 and 89 pilot fuel caps are different,that the 89 breathes thru the keyhole and the 90 doesnt,how do you tell the difference between the two? My pilot is a 90 but has aftermarket tank on it so who knows what cap is on it.The reason I bring this up is because with the rain at LS and my pilot leaks a little gas at fuel cap after I fill up the tank was covered on the top with wet sand and gas cap could have been blocked,so if it was an 89 cap and hole was blocked,I'm not sure if that could be problem or not.


Also I messaged methodical again( on Facebook) with no luck,I don’t know why he’s ignoring me,unless he’s upset I did not agree to go with him the first time I contacted him and wanted to try local first.First time I contacted him he got back to me pretty quick so I don’t understand the ignore factor

Fuel pump flow check:
CAUTION FIRE !! (just a heads up)
1) remove the line to the carb and put it into a measuring container marked with oz
2) using electric start you crank Engine over for 10 sec (use a stop watch) (no ignition on as you don't want it to start)
3) you need 4.5oz approx. in 10 sec
4) if it fails this test then you put line back on carb and remove the return line on the tank and put it into the same measuring container you were using
5) using electric start you crank Engine over for 10 sec (use a stop watch) you need 4.5oz approx. in 10 sec
6) if it passes this test then your check valve is shot
7) if it fails this test replace your fuel filter and use some air and blow through the pick up lines in the tank to be sure they are not blocked and redo this last test
8) if it fails again your pump is shot

Your after market fuel tank:

I am confused.
How does an after market fuel tank use a Honda gas cap ??
This needs more explanation and maybe some pics for us.

What ever your tank is, the fuel tank or cap must be vented.
As long as you are vented you're good.
If your fuel cap vent is plugged then it is an issue.
Tank will build a vacuum as fuel is being taken. Eventually pump can't pull fuel anymore.

Carb:
Can you tell us what carb you are using and what are the jet sizes in it.
Specifically the main jet since this thing blew up at WOT (Wide Open Throttle).
CO

I'm also concerned about the airbox you are using. Could you post a picture of it please?

something I would like to see is the relationship between the locator pins on the piston where they land in the cylinder, I'm sure if they did not line up with the cylinder area between the transfer ports it would have snagged a ring sooner but you are using a CR500 piston with pilot port setup, you could clean an area on top of the piston and mark where the pins are and reinstall the piston onto the crank, no rings no gaskets and check, should be right in the center of the bridge between the ports. the end of the rings should never loose contact with the cylinder, if it is close then consider that when the ring goes past the exhaust port it does open up a bit.

It's aftermarket but made with stock tank but enlarged,I think that atv place in Az sold them and called desert tanks,I will take some pics when I get home tonight

Airbox pics

Gas tank
Doubt if cap got plugged with the cap covering keyhole

Carb is leaking somewhere,I thought I had fixed it. I replaced the 4 screws on the bottom about a month ago and thought it was fixed but apparently not, it’s filthy.Ran out of daylight,I will have the get the jet size another day