Been a while since I have visited but I have missed reading all the stories.  Here is my delima...... Went to crank the bike the other day and sounded fine at first but then I noticed it started sounding a little rough. Pushed the choke in and then it ran better for a couple seconds and then slowly puttered out and died. It will crank back up but dies every time. Naturally, I thought it may be time to clean the carb so I did that but I have 2 screws that are stripped on the top of the carb and cannot get them of to look at the diaphragm and needle. That is issue #1- stripped screws.
Thought maybe I had a exhaust leak from where I put on the dyna last spring. Re-did the exhaust, tin can, and clamps...... No changes.... Still dies.....
Decided to look at the air filter and this is what I find......

Thoughts??

This, is a link...-> Test your Petcock,.. don't just turn it to Prime..  ...

Not riding at all cuz it won't stay cranked

How long did that thing sit? If the P.O. let it sit and the gas in the bowl evaporated and he did that a few times,the carb might be gunked up.
I'd also check fuel flow. Pull the hose off the carb,point it in a gas can and switch to prime.I'd drain the bowl in a clean,clear glass and see how much and how clean it is.

I.m.o. IF it's running good,Good being the operative word,closing the gas off should not kill it. But,ride it,let it shut down,turn the petcock off of prime,immediately,and drain the bowl to see how much is in it. You know when it's gonna do it,so be ready.Don't let it fill up the bowl on ya.  

Hey,guys,can a sticky slide do this?
You might as well put a petcock on it. Maybe won't solve all of it,but they DO fail and they DO cause weird problems AND you got gas outta the vacuum line,so,that's enough to condemn it. I would just go buy one at the Yamaha shop. Save the hassle of trying to be sure you're actually BUYing a real Yamaha part. It's faster,too.

Once upon a time even I had no vise grips.

And flat spots filed on opposite sides help. Be careful not to taper in at the top.Smooth edged  file.

These bikes will run on choke even though the pilot and main jets may be completely clogged. When you turn the choke off (push it in) the bike will die. I like to use pipe cleaners to clean carburetor jets. You can get a set at any auto store. I would pull the carburetor one more time and very carefully recheck and clean pilot and main jets and all the tiny ports using the pipe cleaners and carburetor/choke cleaner.

I crimped the vac line and folded it in half and zip tied it like I saw someone do on this forum.
Did not change anything with the exhaust . Last spring I changed exhaust to dyna slip on and a few weeks ago when I started having problems with the bike dying when pushing in choke, I took out the old crush gasket , put a new one in, and re-did my muffler clamps.
Not sure if this will help at all but as it stands now, with the choke out it runs pretty strong and sounds normal when rolling on and off throttle. However, with choke in, rolling on and off throttle and I get loud pops from exhaust