Should I do a once over everything?

[Thedoggo34]

I’ve just got this bike I’m doing a resto on and when disassembling to rebuild the top end I saw this part of the piston gone, i don’t really want to take it all apart but just seeing what I should do.

 

[pomfish]

I think you already know the answer to this.

The piston is broken and scored up which means the bore of the cylinder is scored as well. The broken chunk of piston is hanging out somewhere in the bottom of the case less the amount that got chewed on its way to breaking free.
Good news is the rod is in one piece, but the engine has gotta come apart.

What make model is it?

 

[Thedoggo34]

I can’t really even find the model on this. The side cover screws are all Phillips heads and all of them are stuck, and I can’t get them off, to look at the inside.

 

[massacre]

You might want to try a manual impact driver to remove those Phillips heads.

 

[manchester1]

Massacre is correct. You need a impact driver. I had a brand new Honda in 1972 and you could not budge one of the Phillip head screws in the case. My dad bought a impact driver and it was a miracle. I still have and use it to this day.

 

[desert rat]

Those drivers are amazing. I have 4 or 5 of them, there is one in every one of my tool boxes and road pacs. Let me impart a process I use with these that will save you a stripped head. Most important is to clean the head out. I use carb cleaner or brake cleaner if its in painted area with a pick and air if it's available. Then I use just the bit and a hammer and "seat " the bit in the head. Then I use the driver and hit it like you mean it, no warning shots here. I don't remember one this didn't work on even some that had almost no slot left.

 

[creia]

What is the make and model of the bike? Is it imported? If so, chances are that those are not "Phillips" heads- they are "JIS" heads and you need a set of JIS screwdrivers. If you try to use a Phillips driver on JIS heads all you will do is screw them up.
Michael

 

[ole4]

What is the make and model of the bike? Is it imported? If so, chances are that those are not "Phillips" heads- they are "JS" heads and you need a set of JS screwdrivers. If you try to use a Phillips driver on JS heads all you will do is screw them up.
Michael

Don’t the ja screws have a dot on the screw head to identify them?

 

[Tom S.]

@creia is right. Phillips and JIS (Japanese Industrial Standard) fasteners look similar but they are different. You need to use the correct tool or you will ruin the heads of the screws and they will never come out. Pick up an inexpensive hammer-type impact driver and get correct bits for it. Everything you need is available on Amazon for not a lot of money.

There should be a dot on the head of the screw to ID it as JIS, but I don't think that's 100% reliable

If the heads of the screws have already started to strip out, you may be able to restore the crossed slots by tapping on that area with a hammer and drift punch of the correct diameter.

JIS Explained

JIS Impact Bits

 

[Thedoggo34]

I somehow ended up getting all the screws out without an impact, about an hour getting them all out, stripped a few but still got em out, to find some metal chunks in the case, surprisingly all of the gears are still intact. I’m pretty sure it’s Japanese can’t find any markings, but now the real problem now is going to be putting it back together.