I blew it up a few months ago. Lost compression quick. I had just bored it and put a new piston in, but ran into electrical issues right after I got it running again. I was able to run it a couple hours after the last rebuild, then it sat with electrical issues for a couple months. Once I got that squared away, I ran it for a good hour or so, then lost compression. I just pulled the cylinder off, and here's what I saw. The piston & cyl are scored up pretty good along the exhaust side.

The piston-

Looks like no oil. Zero.

Looks like no oil. Zero.

That was my thought, too. I didn't mix up the fuel/oil in between the initial ride and the later one. Oil seperated from the fuel, ran oil rich for a while, then poof....

It ran great on it's last couple runs, 10-15 minutes each, shut it down the last time and it was sizzling hot. Ran it pretty hard, maybe too hard?

Bummer man, I have seen that before . My oil/gas mix had too little oil. The gas can I was using had a 4 foot long by 1/2 inch ID hose at the bottom of the tank for dispensing, When I went to mix the oil and gas, I first poured in the oil then the gas, the oil went into the tube and stayed there, therefore not much mixing was going on with the gas. So when I went to dispense the gas, the first tank was very concentrated with the oil. The next tank had very little oil, she ran for about 45 minutes before locking up! Out of curiousity did you mix the gas and oil in a can or the Odysseys gas tank. If you poured the oil into an empty gas tank, then poured the gas next. There is a possibility that the fuel pump sucked up the oil first then gas. On another note, once the oil is mixed with the gas I don't beleive it can seperate.

Hi
This sucks!

How about some more pics of the piston, all sides including top and bottom (inside) more pics of the cylinder and head too, lets get to the bottom of this before you assemble again.

At any time did it seem like or sound like it was running out of gas?

Pics of the spark plug?

Drain out some gas and put it in a glass jar, let it set see if anything seperates, I did this with AMSOIL and a year later it was still mixed no separation.

Any idea what the piston to cylinder clearance was?

Ever pressure test your Engine to see if their is a air leak that can create a lean condition?

Any oil puddled up in the bottom end of the Engine, turn the crank over see any oil on the crank?

The aluminum can be removed from the cylinder with muratic acid and a old tooth brush, warning and caution when using acid, I leave the safety up to you but advise you do this outside and have baking soda and running water ready in case things go bad and you get it on you, face shield, rubber gloves suggested... Once the aluminum is dissolved and removed you then can give it a lite hone and measure the bore.

man that looks rough. what type of premix oil where you running? where do you ride the ody? I am not too far from apex.

your holes look small and far down and apart on the piston...

Wow, lots of responses. Thanks guys, I've been outta town, hadn't had the chance to respond til now. I'll get some more pics up.

The oil was mixed 20:1 in a can then poured in the tank, but it sat in the tank for a few months.

The piston to cyl clearance- I don't recall the # off the top of my head, it was a while ago, but remember ordering it from Ody Salvage, discussed with them, wrote the clearance on the piston, and piston went with the cylinder to the machine shop with direction to provide the clearance.

I drilled the holes in the piston, I think (again it was a while ago), it was per directions I received with the piston. Turbo, those holes look huge compared to mine.

I did relieve the exhaust bridge myself, used a straight edge with a feeler guage to check.

It never sounded like it was running outta gas. Ran awesome, no hesitations. On the last run we went fairly hard at high speed, then slowly cruised a back trail for a minute or 2 to a stop. I shut it down, heard it was sizzling hot, let it cool for a while, then no compression, wouldn't start again.

Never pressure tested it, not sure how. I did check compression, and IIRC it was 130 or so before the last ride.

It blew up at Busco Beach. http://www.buscobeach.com/ Awesome place for an Ody. We go a lot, it's only an hour from here.

My buddy keeps picking on me that the Ody has never survived a ride without a tow back. He was also giving me crap for my toys being only at 33% operational. My 400ex is the only thing that runs outta 3. Gotta have something reliable that starts everytime, haha.

I think the oil was some Yamalube 2stroke stuff I had around.

I just spun the crank over, plenty of oil on it. The plug had oil on it too. The head and top of piston have a little carbon build up.

Piston-

Head-

BTW, can you add multiple pics to 1 post?

Plug-

This does help my post count though, haha.

edit- sorry, crappy pic. It's kinda black/gray, coated with oil.

piston bottom-

Crank and rod- Notice the discoloration on the rod, too hot?

Piston side-

Cylinder

Just for the hell of it- my 33% running toys, ha.

I am sure someone will chime in about the pics, I do not have quite that much experience under my belt yet. The plug looks rich though, was it a fresh plug or an old one? I think you can add up to 6 attachments per post, you just keep clicking on add attachment.

I have heard a lot about busco. all the pics make it out to be mud city so I didnt know if I would have fun there or not. I will have to plan a trip as well. Are there any mud free trails that I can take at high speed?

It was a fresh plug.

There's plenty of room to open it up at Busco. The muddy spots are a fraction of the wide open dune areas to blast around in. My buddy has a 4x4 Kodiak, and a 400ex, the kodiak always gets left at home for those trips. It's awesome for sport quads and a pilot/ody. They've been working on the place a lot, setting up a couple tracks, some with jumps, etc. There's a lot of sandy hill climbing stuff, a drag strip, and a couple areas with long, flat sandy straights where you can keep it pinned for a while.

Something to check... Is that oil on the crankshaft lobes? Did you have to add balancer oil very often,like after 3 hours of riding, and if so, do you wonder where its going if not leaking out on the ground?. I am experiencing a problem right now where balancer oil is getting from the side of the case where it belongs to the other side, it coats my plugs after only an hour or so of riding and looks like carbon build up,it also creates excessive build up on the exhaust port, top of piston, makes rings hang, looks just like your parts in the pics. I believe the oil is getting past the crankshaft seal or O ring. I just havent tore into it yet.If you think that is part of your problem or just another problem,and now that you have the top off I would get the O ring and seal replaced. Good luck and let everyone know what you find with the seizure...

33% X 4 = fun. I like the small blue one. You could brek it out after a night of red and white ( budweiser). I know I would ramp it over the cans to see how many I could clear. A back pack of batterys should get it up to speed. Where did yo say you lived, close to Wichita Ks ? Um.

My boy just turned 4, his powerwheel doesn't count in the 33!!!! Just getting him started though, he loves it.... He's getting trained.

Not near Wichita, can't wait til he's old enough to take out though. He wants it!

(near Raleigh, NC)