So I've got a stihl ms290 chainsaw that the spark.plug threads are stripped n I saw on this site 2buy a 14mm heli coil kit but there are 3dif types in 14mm size. There's 14mm×2.0, 14mm×1.5, and 14mm ×1.25. Which is proper kit for my stihl ms290 chainsaw

SOURCE: no spark in stihl 025 chainsaw. I replaced the

Where did you get the coil? How did you gap the coil? Reply below please.

This tests the entire system:
Ignition Coil Test by SmallEng.com
http://www.youtube.com/watch?v=L7WNBDRG4C4
You may need to use a jumper wire between the threaded part of the plug and the cooling fins. You do not have to bend up the electrode.

Ignition module gap
Place a business or index card between the fly wheel and coil, rotate until the magnetic attraction pulls everything tight together. Tighten the coil screws, rotate the flywheel until the attraction eases and remove the card. Ensure nothing contacts when flywheel is rotated.

If you have more questions or need additional help please reply below and I will get back to you. Thank you for using FixYa and Good Luck. HTH
Lou

SOURCE: spark plugs are stripped

Yes, go to auto parts, and tell them you need a spark plug hole repair kit, very easy to install, just follow the directions.

SOURCE: My Stihl 029 chainsaw cylinder threads are

If you wan to try to repair the head you would be looking for a product called a helicoil.

SOURCE: I have a Stihl MS290 and the threads on the

The plug thread is 14mm, check out E Bay for a 14mm heli coil kit, they come with instructions on how to use, practice on an old cylinder first if you have one.