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View Full Version : Echo SRM-210 Trimmer - ZAMA RB-K75 Carburetor


hydrosmurf
04-26-2010, 01:15 PM
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.



http://www.partstree.com/images/diagram.php?src=r&ilFN=D%3A\EMPARTweb_52\Catalog+Data\EMP_IMG\ECH\Images\images\CARBUR~1\RBK750~1.TIF&ilSC=10&ilIV=0&ilBR=0&ilIF=G&ilRE=8&ilSH=0&ilEG=0&ilRO=0&ilSC=24

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.

Regards,

MP

hydrosmurf
04-30-2010, 03:25 PM
Just wanted to bump this back up. Maybe someone will have time over the weekend to respond. I could still uses some insight on this.

MP

Diesel59
04-30-2010, 07:09 PM
These little carbs are always a pain.... alot of times you spend more time fooling with them then they are worth. If the carb was all gummed up with "Old gas" u probably will need to install a rebuild kit. This kit will come with all of the little diaphram gaskets which are the important things in these lil guys. Most times when they become brittle they will cause the carb to not flow fuel like they should. Also if you spray the diaphrams with carb cleaner it will dry them out real quick (I've done that a few times)

That little brass screw and plastic plug really shouldn't be messed with too much. These carbs run so lean from the factory due to emmisions. But a lil adjustment shouldn't hurt

Also depending on what kind of oil was mixed with the gas check the exhaust screen in the muffler. Alot of times it will get clogged and cause the trimmer to run strange and not get up to full power.

dutch1
04-30-2010, 08:24 PM
If your carb is exactly like the one in the diagram, I believe there is only one O ring and that is part #8, between the carb body and the rotor cover. There is a nylon roller that rotor cams on and it sits on a pin inside the carb body. If the roller breaks the engine will idle erattically. I've opened a few of those carbs up and found two pieces of the roller in the bottom of the carb. The roller is illustrated just below the oring.

hydrosmurf
05-02-2010, 12:04 AM
So after using the trimmer for about an hour today, (it is somewhat useful) I noticed something that I haven't before. When the trimmer is in the normal position, that's when it doesn't rev up to full speed without bogging and almost stalling. When it's sitting on the ground (when I'm adjusting the high speed screw) it revs up pretty good. When I have it rotated 90 degrees from normal to edge along the sidewalk it works well too. After I realized this I turned it upside down and it also works pretty well. This I thought was strange. It has nothing to do with the fuel filter not being in the fuel because I checked for that. What else could cause this?

The reason I haven't bought the rebuild kit for this yet is that I don't know for sure that it is going to fix it. I remember reading that there is a non serviceable check valve somewhere inside the carb. Also, if I can't remove the high speed screw, how do I really get this carb completely clean? Should I just buy a new carb?

Has anybody experienced something like this and just had to replace the diaphragms to fix this?

Thanks for all the responses so far.

MP

The Lawn Ranger CT.
05-02-2010, 02:09 AM
when you checked the exhaust did you remove the muffler~? I found on my stihl trimmer was doing the samething and carbon had built up in the out port between the motor and the muffler, I made sure the piston was all the way in the up stroke,(to make sure none of that crud fell back into the cyl. head) and scraped out the carbon, then it rev great.

Merkava_4
05-02-2010, 08:54 AM
They got the whole carburetor on ebay for $60 with free shipping.