What are some of the symptoms or conditions from a failing reed valve. How can I tell if mine is bad or not. It is the original one from 85.

The originals are metal reeds i have never seen a set go bad. Whats your Engine doing?

It runs fine after warm up. and its got good enough power to spin donuts n pavement. But after it runs for about 15-20 min or Ive also been noticing after running in mid range for a short period of time it seems like someone pulls the spark plug wire off. Give it gas and it just severely boggs and dies. After it dies if you pull the choke it fires right up and will stay running without the choke on but doesnt have much power after until it cools down. An I noticed that the head on the exhaust pipe right off the motor (( Internal Combustion Engine ? )) is starting to turn a shade of white on the outside.Its got the correct jets according to the manual. seems like its leaning out all of a sudden or forms an air leak. I just didnt know any of the symptoms a bad reed valve will cause.

Do an Engine leakdown test and make sure you aren't leaning it out with a leak. Search around for the how-to. Also known as crankcase leak test, or pressure test, etc.

When it stalls out, have you pulled and examined your plug? Is it very light colored, beige, brown, or black?

Do a plug chop and verify your jetting at idle, 1/2, and wide-open. Search around for a plug-chop how-to. Very simple and important. Or you can use an EGT gage if you've got one plumbed in, but the chop is simple and fast.

What altitude are you at? This may have a factor on your jetting.

What octane fuel you running? Oil?
What fuel/oil ratio you running?
Any mods to the Engine, or is it bone-stock?

Are you running the stock tank with the fuel pump or an aftermarket one that has no pump just uses gravity feed? Sounds like your rings have melted into the piston and after it warms up the rings no longer can keep the compression up. Do a compression test cold then do one after it boggs out.

ill give these a try this weekend and let you guys know what I fine . Thanks for the input.