Hi everyone!
After reading through many of these threads, and following what they said, my bike is still having issues running. Let me describe the problem:
It starts up and idles relatively fine, misfires here and there.
Once it is revved, it stumbles over itself and misfires hard. The idle also stays up, and slowly drops back down. If I try to ride it, the bike will bog and almost die after taking off from a stop, as well as other times it’s being used to accelerate. A friend says it seems to stumble in its middle range but picks up on top. It started randomly, after I was out riding. Hasn’t run the same sense.
What I’ve done to try and fix this problem:
Replace the coil and spark plug (adjusted height of the spark plug as well). Cleaned the carb multiple times, played with timing, made sure it was getting enough fuel (the tank let’s it out like a waterfall), valve adjustment, air box was clean no issues, sprayed the carb with starter fluid to check for vacuum leaks (none but had some in the past that I fixed), lastly we went in and drilled the mixture cover and adjusted that to two turns out and it’s still having issues!
Any help would be absolutely amazing, I would like to fix it on my own but a shop might be the next call.
Thank you guys so much!

Welcome to the site as a new USER. Have you checked (carefully) the coaster enrichment black plastic cover? Very easy to miss small cracks.

First, what bike do you have? What mods have been done? Do you know which jets are installed?

As Muniac alludes, your symptoms are typical of a vacuum leak, or otherwise a mixture problem.

Thank you so much for your reply, Muniac, the black plastic cover on the right side of the carburetor was replaced recently. The last one had a pretty bad crack in it. The new one maybe has a couple hours on it, and didn’t react to any starter fluid. We also removed and looked it over and it seemed fine.

Thank you too peejman, it’s a 2001 Yamaha xt225, I believe it’s completely stock, American model. The previous owner told me a shop worked on it and they may have changed the jets. I’m not sure if they are stock or not, I havnt compared the jet sizes. However, it was running great before any issues occurred. I would assume that if it was a jet issue (other then the jet getting clogged) then it would have happened right away?
I’ll have to check vacuum leaks again, would you have any advice on mixture problems. I was able to get to the mixture screw but playing with that didn’t seem to help or hinder the bikes ability to run. Thanks so much for your help!

So it was running fine and now it's not. If stock, it probably has a #40 pilot jet and a #125 main jet. If a shop changed the jets, they most likely would have removed the plug over the mixture screw and adjusted that as well.... assuming they had any idea what they were doing.

Get a flashlight and look inside the tank for any debris floating around on the bottom. You've cleaned the carb a few times. Have you found any debris, and if so, what did it look like? Do you have a fuel filter installed?

Where did you set the float height when you cleaned the carb?

It sounds really lean, which is indicative of either a vacuum leak or clogged jets. The intake boot between the carb and cylinder is a common source of vacuum leak. It's also got a rubber vacuum port plug that will rot out and leak. If no vacuum leaks, sounds like a clogged jet. Since you've cleaned it a couple times, it sounds like recurring debris which is (unfortunately) usually rust in the tank. But we can go step by step and figure it out.

All the times I’ve cleaned the carb I havnt seen any debri, but cleaned anyway just in case. I replaced the petcock and when I did that i noticed the hoses that go into the tank have filters on the end. Just to be sure, I attached a fuel filter this evening, along with brushing out the jets again, cleaning mixture jet and setting to 2 circles out, I also adjusted the float bowls to the recommended 14.1-15.1mm.
I noticed that a o ring was missing on that black cover towards the end of the carburetor, got really excited. Replaced that o ring as well. She seems to idle smoother now but the same bogging issue is still occurring. Just to make sure of no vacuum leaks, it was sprayed again with carb cleaner, and no results popped up from that either.
On the topic of it being lean, the spark plug is turning black and not white.
I really appreciate all of your help! This is quite the conundrum!

How warm is the engine when you're getting this bogging issue? These engines are notoriously cold natured, it takes at least 5-10 minutes of riding to get them up to temperature. Sometimes longer if it's cold.

Are you using 100% gas?

Since you've cleaned the jets, what's in it? They should have numbers stamped into the jet that says what size it is. Any shims under the needle?

I see that Edgewood NM is at about 6700ft. That altitude will have an impact on the bike, the thinner air can make it run rich. Try removing the air filter cover (not the filter, just the cover) and see if that makes any difference on a short ride.

Hi Alice, it's good to see another local with an XT 225! I am in Albuquerque, and since getting my 225 I have gone through plenty getting it to run correctly around here. One important thing is even though I have the snorkel removed and done the Z1 mod to the muffler, it still can't use stock jetting. I made an adjustable mixture screw so I could fine tune it while out riding, went to a 42.5 pilot and a 122.5 main. With the 125 stock main it would load up and puke.
If you could use a hand with yours, or want to ride mine to see the difference, just let me know and I'd be glad to lend a hand.

Have rode my XT to the top of Mt. Lemmon, AZ with no problems. Elevation is 9102 feet at the overlook I turned around at. Bike is completely stock except the exhaust is opened up a little but less than the Z1 mod. Was down on power but ran fine. Rode around all day with a couple of buddies. Even on my home turf I ride to nearly 8,000 feet often without trouble. IMHO, elevation isn't the problem.

rocmoc n AZ