Judging from your first pic, the top of your piston looks like its been smashing bits of metal between it and the head...possibly bits of con rod or main bearing debris or even a lost wrist pin clip??  Pic also has your piston ring rotated around and overlapping the pin, which it should not...maybe its fallen out?  You might want to look at taking it to a reputable shop. Hope you get rolling again soon

I too noted that texturing around the the piston top (but not on the top of the crown). Would that area correspond to the "squish zone" (and so little clearance between the head and the piston)? It sure looks like something was being driven into the piston.

Alexdukes ... Do you have a picture of the (underside of the) head?

I do, see attached.

I think the guy said it was a new piston. 

The problem is, i live in the countryside info France, reputable garages are few and far between, so some amazing guidance on how to move forward with my own two hands would be amazing!!

 

Thanks guys so far

Yes, the piston marking on the crown matches the squish area. Its hard to tell from the photos if that marking is due to debris getting smashed between the piston and head, or bad detonation occurring in there.

If you only ran the engine without oil for a short while, that may not be the cause of the problem and is just serving to confuse us.

I certainly don't think the ring area of the piston looks healthy. On the other hand there doesn't seem much wrong with the bore in the photo, but I think it needs to be inspected carefully and measured.

After further conversation with my son, he has said he has probably run roughly 2 tanks through the engine without oil! I nearly crucified him!

So am i looking at trying just new rings as evrything else looks vaguely ok? Or new piston aswell? Need to get stuff ordered as everything takes a dogs age to be delivered in France!!

 Blowing the pictures up, there is alot of small specs everywhere which usually means the rod bearing. Especially with that amount of time with no lubrication. If not the rod the mains could be the culprit.  I would not just throw a piston in without some thought into what all is wrong.

I'm sorry for Alexdukes situation, but I'm eager to learn from it as well. If a (connecting road and/or main) bearing "went", how would one assess that? What would you "feel" when moving the crank through its stroke? Would it grind or stick or ... ?

Thanks guys, Thanks d2w, yes, as i am fixing this myself, i need some guidance of what i am looking for?

39 minutes ago, oni nou said:

Really no opinion?  Ha, Ha!

Hard to fix a bike on the internet. Luckily the Pro motor lubes the mains by the transmission oil. The rod can be checked for vertical movement, Should be no up and down play. They always have play sideways. The crank should spin freely, but you are turning the flywheel and clutch basket. It really should have the lower end flushed out. If you go any farther the engine can be removed without removing the skid plate. Good luck.

21 minutes ago, lineaway said:

Really no opinion?  Ha, Ha!

That in depth step by step how- to for a person who has zero knowledge should be of enormous help. Ha Ha. ........It will have to be answered by section swept he is the one who can be bothered to type up more than a couple of sentences at a time HaHa.

Actually google Jim Snell video`s on you tube. That will at least have you familiar with the motor. Yeah, if you get Section Swept and Oni nou bantering. At least everyone will be amused.

  

2 minutes ago, lineaway said:

Actually google Jim Snell video`s on you tube. That will at least have you familiar with the motor. Yeah, if you get Section Swept and Oni nou bantering. At least everyone will be amused.

  

As you well know lineaway  I only ever do anything to amuse myself. .....Keep up the good work  don't worry I will not be giving any more opinions... poor old Nigels ego gets bruised.

 

 

Alexdukes ... Just some basic questions ... What do you see in the oil when you drain it? What kind/size of debris is stuck to the fill and drain plug magnets? I believe that diesel fuel is a safe solution to use when trying to flush debris from an engine.