MZ TS250 74' new piston and bore

[DARKEST]

Hi
I just found this forum and is very happy for that as it seems to be a place for help and guidance.
I have a MZ TS250 74' where the piston is worn out an so is the barrel bore. I would like a new piston and a refurbished the bore on my cylinder barrel. The present piston diameter is 69.47mm. I have some questions before I purchase a new piston and make arrangement with a bore shop.
1. Is the next size 70.0mm? (there are only small scratches in the bore)
2. What type of piston should I chose? I can read that the original piston K20 is preferred as the temperature expansion koefficient is smaller and suit the recommended tolerance of 0.04mm between bore and piston. What is the original piston? HAL, KAL, Megu, Almot?
3. I can read that the tolerance is 0.04mm between the piston and barrel. This should give a distance of the piston rings ends of 0.2mm. This is very precise and is it even possible to do this? - or is it just piece of cake for a bore shop?
4. I assume the first thing I should do is to purchase a new piston and give it to the bore shop with my preferred tolerance?
5. After finishing the new bore the ports should be finalize with a chamfering right? A good bore shop would do that?

Your experience will be appreciated.
Thank You
/Brian

[Guesi]

I would prefer an original piston. The Almot have no good reputation.

Megu or HAL are the original producers.

Price for an original piston is 79 Euro.

[Puffs]

Following a biased and flawed moderator choice (someone posting aggressive personal attacks is rewarded, while my technical posts are removed - behind my back & without any justification!), I have withdrawn from this forum.