echo srm-210 trimmer - zama rb-k75 carburetor
A used SRM-210 trimmer was given to me in a non-running state. I removed the carb, and gave it a good cleaning with carb cleaner, but I stopped short of removing the metering lever and needle. With the information I found on this forum, I was able to locate the mixture screw (high speed needle) with the plastic cap on it. This particular carb only has one adjustment screw. I removed the cap, and I was able to turn the screw with a regular driver, but I was unable to remove the screw completely because of what looks like a brass insert. I didn't know what to do at that point; so, I decided to put it back together while I still remembered where everything went. Once I got it back together, it fired right up. Yeah!
However, it's running lean. It has been starting right up, and it will idle perfectly, but it struggles to reach full speed. Even when it does eventually get there, it surges up and down. Right now I have the high speed screw turned all the way out (turning it in makes it run worse). The top of the screw head hits the bottom of this brass insert preventing me from turning the screw out even more, or ideally, from removing the screw and blasting the opening with carb cleaner. Below is a break down image of my carb. Item "10" is the plastic plug, and item "11" is the high speed needle. The picture doesn't show the brass insert. On the ZAMA website, they have a parts breakdown of a generic RB type carb, but they call it a "main jet" and they say to remove it to clean it. They say to inspect an O-ring, but I didn't see one of those.
What do I do? Do I try to get rid of this brass ring so that I can remove the mixture screw? Has anybody been able to remove this screw to clean the carb? Should I just buy a new carb for it? I new carb is going to run me $60.00, how do I know if that is going to be worth it, ie, how do I tell if the rest of the trimmer is going to last $60.00 worth of carburetor?
Is there some other trick to go about this? I have spent a lot of time on the internet trying to find the answers, but it seems like nobody has ever been prevented from adjusting the mixture screw enough to make the trimmer run correctly.
I had a look at the store, and the new Echo trimmers have carbs that look exactly like mine (single mixture screw with a black plastic plug covering it).
Any help with this would be greatly appreciated.