I'm wondering though, if the cylinder was bored correctly with the proper clearance. The piston & cylinder were scored up 2/3 of the perimeter.

Any thoughts on it?

I just checked the balancer oil and it was still full. I haven't added any since the rebuild, but it only had a few hours of run time. Yup, that was oil on the crank after spinning it over. How much oil should end up in the bottom? I know 4-strokes ok, but this mixing oil/gas thing... I guess it seperates and gets just enough oil to coat everything?

Thanks, good luck with yours as well.

2 stroke lubrication is scant, your lubricating with a solvent its a oil fuel mix, when the mix takes its path through the Engine some of the gas/oil will fall out of suspension and collect in the bottom end, once the Engine is up to temp and you make a long WOT (Wide Open Throttle) run most that oil that has fallen out of suspension will be picked up and run though the Engine and burned with the fuel.

With todays oils 2 stroke last much longer than in days past.

Its always good to pull the choke and let it idle a little, let the Engine load up some before shutting off after a ride trip and before storage until your next ride, this gives a good coat of oil on everything inside.

I have a few questions on the motor (( Internal Combustion Engine ? )). I been looking ove rthe pics and looking over the pics. Does this motor (( Internal Combustion Engine ? )) have any air box mods. Are you using stock set up with the single stoke tube. What air cleaner. This pics bring back bad memories. There may be clearence issuses but you would need to measeure them up to be sure. Did you you use a trusted machine shop for bore. Defenty a bummer. The pin look used, was it new and with new bearing? The crowm look like it swelled up and pinced the rings or a helty does of sand went thu it. Coat finger with two stroke and swipe the intke boot and then rub finger together. Yes, play gyno with the boot. If its gritty will this may have some input on issue.

The airbox was stock with lid and single tube. I installed a new well oiled Uni filter with the last rebuild. I did like you said, coated my finger with oil and rubbed all around the intake, and I didn't feel any grit. Gyno with the boot, mmm, I like it.

It was a new pin and bearing. Pin is still nice and smooth, bearing looks fine.

I had it bored at a local machine shop/VW parts place, been in business since the 70's. They have done a bunch of other work for me in the past, they were a huge help in building up my bug motor (( Internal Combustion Engine ? )), but I'm thinking they screwed up this time. The rings are almost flush with the piston all the way around. I'll put the calipers on to check the clearances out.

I have a new connection now, a guy that works at a local Honda bike dealer. He's into racing and knows 2-strokes well. But if I could have it hoserized....

I just watched some Nitro Circus with the boy. He says he wants a "mud bike" so he can "back flip it like that guy" (Pastrana), lmao. "Can we get a mud bike fo me tomollow?" I told him he needs to be an expert on the PW, practice everyday, then we'll talk about an upgrade. Mommy does not like this.

Piston, measured across the skirt, perpendicular to the pin- 3.129"

Cylinder, measured across several spots across the top- 3.138"

So, .009" clearance- too much? The manual says the service limit is .006. Was it bouncing around in there?

There are other posts here regarding clearances for the Wiseco piston but heres a start. http://pilotodyssey.com/PO/viewtopic.php?t=5307

Re measure about 10MM from skirt and mesure it in an x and y. X being intake to exhasut and y being 90 deg. You should see a diff. As far as new filter good to see no sand. The bad news is its needs more air to jet correctly. I would look at a mod for the lid or second tube. See what the other 350 guys are doing. I have seen this before. If it air test and clearenced right. It will require a air intake mod to keep it running or you most likely keep eatng piston. The other thing would be install a water cooled head. Highly recomended for crown swell. What is happening ( quess) is the piston is swelling and once it filles the cylinder in a lean condition it swell up because it alredy tight in the jug. then the rings get pushed against the walls due to upper section of the piston swells form the heat and the ring have no ware to go but tight. This is one resaon ring gap and clearenc is so important. If you put straihgt edge on piston you will notice that the upper portion of the piston is smaller in dia. this is why. The air issue is just that not enogh for propper jetting once you go past first bore. It causes yo to run lean so the motor (( Internal Combustion Engine ? )) clean out and not fourstroking. TYhen once enough heat is in cylinder not being wicked out or not enough fuel to keep cool the piston canonly do one thing, Grow. Take you motor (( Internal Combustion Engine ? )) o the guy and have him check it out checking clearences with the wore stuff just to make sure it not a clearence problem if it wasent get head and air intake mod and read up on plug chops and propper jetting. Nuke em has good info and I would bet "H" does as well. I know Stix has a good set up for water cooled head using a pump that works reducing the head temp and keeping swell in check. Hope you get it up 70% and put some woop a_ _ on your buddie. I know I would if I could. It will make you feel better. Good luck and keep us all posted I enjoy reading and looking over the pics.

I have had several pistons that looked just like that in my early days. It took me a while to figure out that .003-.004 is just too tight for the air cooled 350s. I also had a bad seal(air leak) that compounded the problem and troubleshooting. All my air cooled 350s with the Wiesco pistons, I run .005 clearance. Be sure to let them warm up good before really getting after it. My experience is the alloy/material in a wiesco swells slightly more when heated than a factory Art Honda piston. Like these guys mentioned, a liq cooled head will save LOTS of issues too. I suggest a .005 bore to piston, and a leakdown test before running her again.

Gary

Here is a good upgrade and general info post I wrote way back. Lots of good geewizz info....

http://www.pilotodyssey.com/PO/view ... disclaimer

You cant go by the measurements taken off that piston once its damaged that much they will not be reliable, chances are by time that piston and cylinder got so hot the oil film was removed and the piston seized the piston had collapsed some, notice how hard it was to remove the piston pin that's because the piston is deformed.

Have you cleaned up the cylinder bore yet whats your next move?