I have a Homelite string trimmer, Model UT22600. The primer bulb is broken and fuel is leaking through it. I think that is not a big issue and didnot replace it.

Right now, trimmer runs for 2 or 3 minutes after starting at half chroke. It does not allow me work at "RUN" stage. When I squeeze throttle in full, it stops immediatlely. I am frustrated and thought spark is flooded. But changing new spark is NOT improved.

Manual says it should have pressure in carb. Is primer bulb the issue?

 

I don't know if the primer is THE issue, but it is an issue. A broken primer allows the carb to draw air instead of fuel.

 

Manual says that +30 PSI pressure in carb is the fact when it runs. I am going to replace primer bulb to see what's happening.

 

Depends on where you're measuring pressure. +30 PSI is not in the primer circuit.

 

I have replaced the new primer bulb. Trimmer is getting better.

But one more issue is that it does not reach high speed when pulling throttle in full, even it was chroked after warning up. However, it does run high speed when pulling partial throttle.

 

Back out the high speed mixture screw a tad. It's the one of two next to each other that is closest to the air filter end of the carb.

 

Thanks Cheese for your help!
I did what you told and back out idler screw a tad as well. Trimmer is working perfectly!

 

Great Glad I could help.____________________