Good afternoon Yamaha gurus. I have a RT2. Bought it three or four years ago, and I have rode it around, but, it’s not running right. I think the correct saying is, it’s loading up. Before I started messing with the carburetor, I would ride it, and all I have to go on is watching YouTube videos of guys riding the same bikes and seeing what they sound like as they go through the gears, but it’s sounding like it’s getting too much gas. Now when I twist the throttle all the way it runs like a scalded ape. So I’ve asked on some forums on what to check. So, the first thing I got was the  OEM O-ring and went in there and sure enough it was all dry and brittle. I replaced it put it all back together. Rode  it still doing the same thing. Took the carburetor back off went through all the jets, made sure they was in good shape not stopped up and  cleaned them blew them out with air put it back together and still running the same way. Took the carb back off and pulled the needle valve seat out, and there was a little piece of something down in there, it wasn’t from anything in the carburetor, but it wasn’t allowing that seat to go all the way down. Got it out put it back on, doing the same thing. Lowered the needle valve one notch, same thing. Went to the top notch and it seems to run a little better at a lower speeds, but still not running like it should. Some people have said I need to adjust the timing. The tech manual says pull the head off and use the dial indicator. I’m not the best mechanic in the world, but, there’s just nobody around where I live that works on these old bikes, So you have to make the choice to learn how to work on them. I know you always start with the simplest thing first. I swapped the spark plug wire and put it on a brand new spark plug, same thing. I’m just lost. Could y’all please give me a checklist to go down and start checking. And give me a list of any tools that I need to buy to work on them. I have Deets telephone number and I’m just hesitant on calling him and bothering him. I probably talked to him seven or eight years ago when I ordered a wiring harness from him and he told me that he and some buddies drove all the way to California from North Carolina on these things. That’s what I wanna do, I wanna ride this thing like it was 1972. They’re made for riding and  not looking at. Please, point me in the right direction. Thanks in advance from South Arkansas!

A worn Needle Jet , and maybe worn Needle too might well be the the source of your troubles .
The Needle Jet is hard to find these days , but does pop up on Ebay occassionally .
I'm pretty sure I have a spare NOS one buried away in my spare parts stash .
If you're interested PM me .
 

I’m no expert, but it looks brand new. No sign of any wear, and I took my magnifying app on my phone and looked it over. Do you think I need to get that, or a rebuild kit. You never know if someone has worked on it and put the wrong keys  in there. But it starts easy (well at least
when you bump start it, cause it kicks back like a mule, even with the decompression lever on, when you kick it)and will idle all day long. 

Not mistakenly leaving the choke open?, the fact that it gets past it & takes off makes me think along those lines. Blocked air jet leading to the needle jet could do similar. OEM Oring is a tight fit into the bowl so should be ok. If that leaks you wouldn't be taking off on full song it'd just stay limited rich. Is the needle clip held down by the spring plate not sitting on top of it?. As i think SWOOP said, worn needle jet & needle but eyeballing with it out of the carb wear or elongation should be visible if its running that bad. I always say exhaust, but not in this case if it revs out on open throttle. When you had the needle jet out--if you had it out--did it locate back down on to the pin at the bottom that guides its orientation. Slide guide pin not gone missing. Cutaway pointing back to the aircleaner.