srm-225 trimmer works but has a few issues

So I have an srm-225 straight shaft trimmer that I have had for about 4 years. I am very satisfy with its performance but within the last year and a half of so I have been having trouble with starting it. Most of the time I have to pull the starter cord multiple times to get it started. After I get it started I have to wait for it to warm up before I open up the throttle or else it will shut off. I will use it for about 20-25 minutes doing the trimming around the front of the house and then shut off and put it down meanwhile I do the mowing. 15-20 minutes later I pick it back up and start it again and it requires multiple pulls to get it to start and it needs to warm up again before I open up the throttle. "WTHeck, I just used it 20 min. ago"!!! I was looking online about how to troubleshoot this problem and I stumbled upon spark arrestor cleaning videos on youtube. I took apart the housing to get to the muffler and remove and clean the spark arrestor screen and what??? (no screen). I've never taken it apart. ( unless it was taken off the time I took it in for service like 2 years ago and never got put back on) Is it normal to not have the screen? Anyway, recently I have rebuilt and cleaned the carburetor, changed the air filter, changed the fuel lines, changed the spark plug and seems to be working fine except for the starting problem and also getting some gas/oil residue from the air filter compartment area. Can anyone give me a little bit of feedback on these issues? I greatly appreciate it.

Primer bulb could have crack or hole. Part #: P005003120

Check the breather. Might have some pressure building up in the gas tank that can't escape.

Repair shop maybe removed the screen. It is a little square metal mesh grill secured by one screw. If nothing, good! That think clogs once in a while.

Try the trimmer without the muffler ( it will be very loud )
If it runs significantly better then you most likely have a clog in the muffler
And yes workshops ( like mine ) regularly remove these screens although after cleaning I do try to remember to replace it.
You can buy a new one they are a service item and sometimes when they are really hard to clean I just replace them.
It won't hurt the trimmer running without it but there is nothing to stop bugs making a home inside your muffler and plugging it up if it is not there.

Lawnboy18 said:

Check the breather. Might have some pressure building up in the gas tank that can't escape.

Repair shop maybe removed the screen. It is a little square metal mesh grill secured by one screw. If nothing, good! That think clogs once in a while.

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It's called the spark arrestor screen and it's probably on the side of the muffler. You'll most likely have to pull or remove the plastic cover to see it and remove the three screws from the small side plate or cover to see or get to the screen. Clean the screen with a small wire brush and replace the screen. You'll find them on trimmers, blowers, edgers etc.

https://www.youtube.com/watch?v=SF76eBZ8XJU

No, I am talking about the fuel vent. It might be clogged causing the gas to escape from the air filter.

If it runs ok eventually I think it is a primer bulb problem. We have an Echo Hand held blower that will run excellent but if you do not pump it up real good it will do start but not run full throttle for an extended period of time.

This sounds very similar to what happened to mine. Mine was also about 4 years old and I only use it on weekends at my house, not commercially. I replaced the carb last year since realizing I left the fuel in it over the previous winter. A new carb was around 25$ I think and super easy to install. Everything runs great now.