I'm thinking of repairing the engine of my 1975 DT250B. Currently the standard one (69.96mm) is included.
There seems to be a scratch inside the cylinder, so I'm thinking of putting in a 71.00mm one.
Please tell me about piston kits that can be used in this case.
When I searched on eBay, I found that a WISECO piston kit with a size of 71.00 mm was sold for DT250 (part code: 234M07100)
Is this usable?
I would be happy if you could also tell me the evaluation of WISECO pistons.
 

Can't speak for compatibility, but used Wiseco prolite pistons in my CR500s and had no issues. Beat the crap out of 'em, lol.

That's a huge jump in size for a "scratch".  Yamaha original, Wiseco, and Wossner should all be pistons you can find.  All are excellent quality.

I have the exact same bike and i had to go to 70.50MM with a Wiseco. Wiseco doesnt have .25 so going 10 over isnt an option at least at this time with them. They make excellent pistons. Depending on how bad the scratch is you might be ok with a simple hone and new set of rings.

Can you post a picture of your scratch you can use Imgur, google photos etc 

WISECO seems to be highly reliable.

Thank you for your reply.
I know that there is one every 0.50mm.
The cylinder seems to have deep scratches, so I'm thinking of going over 1.00mm instead of 0.50mm.

Due to various circumstances, it is not possible to measure the cylinder before purchasing the piston.
I would like to purchase the cylinder and piston at the same time.
Is there any problem with the WISECO product, which has the piston and other rings integrated?