Piston scoring

Some people will argue that you would never get the rings back into the same position they were broken in to. Others would argue That rings can walk around in the ring groove anyway.

I always figure that while you have the top end off, throw in a set of rings, but the budget minded might save that cash for lap dances. Re-using the rings is perfectly legitimate, but I would tend to replace. In other words, I suggest new rings, but it is by no means mandatory.
 
Well if you dont replace your rings I suppose its not all that difficult for you to pull it apart and replace them later right? Im curious to see how she fares when you get her running again.
 
Rings rotate at around 1 revolution per 7 engine revs IIRC. ADC makes a good point that they must go back on the same pistons in the correct positions. If you fit new rings the bores should be fresh and if they are going to be honed you might as well use new pistons as well.

Just fit the old ones and run the thing. It ran fine before you stripped it and made great compression.
 
So, I've packed up the cylinders, pistons, pins and my 2 cranks and will be going to see Gord Bush in the morning for some measuring / advice.

One thing I checked and was concerned about is there is a tiny amount of play with the piston pins in the rods. Interestingly this is the same on both of the cranks I have. Almost leads me to wonder about the size of the pins, which while are a perfect fit in the pistons they came with (aftermarket from MikesXS) the fact there is a tiny amount of play in the rod ends is worrying.


After some research I confirmed the tolerances and that they need to be checked with a bit of oil on them, not 'dry'. So will double check.
 
Your machinist should be able to check small ends and see if they are out of round.
Yamaha allows quite a lot of slop (sounds like loose tappets)
Have him mic the pins, need to have a reading in 0.001mm or 0.0001"
 
Took everything into Gord Bush Performance here in Toronto and had Gord himself check it all out.

I'm replacing the pistons/rings but keeping the same bore size. They're going to clean up and hone the cylinders. The play in the pins is fine and they're all good.

They're also blasting the entire engine clean - cases, side covers, cylinders, head, tappet covers the works, along with a couple other bits and pieces (the brake plates for my hubs and the original Honda tools for my CA95 restoration).

Should have it all this week - working on getting a new set of pistons from XSCycle.ca (Andy) who I got the ported head / XS1 cam / copper gasket from. He does XS650 pistons with the fancy coatings on them and has the right sizes for me.

Gord recommended sticking with the same size - cylinders are good. Turns out boring cylinders is now $80 a hole - much more than the $50 I remembered from years ago :P So a $20 hone is better than a $160 bore job any day.
 
Likely overheated it (the one with bad scoring he suggested had technically seized) and running rich washed the cylinders.
 
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