# Zama Carb is making me crazy



## scotty088 (Jul 4, 2008)

Hi all,
I have a Echo weed eater model SRM210 serial#08354265 It will only run with full choke on,will not throttle up at all.It just dies.I have completely diss-assembled to bare block.No air leaks,exhaust is clean.compression checks out with reliable gauge at 100#Installed new spark plug gapped at .030 spark is good.It has a Zama RB-K75 rotary barrel carb to whitch I have installed a diaphram kit with a new inlet needle valve kit.I have been over and over this carb with carb cleaner and compressed air it is clean.No air leaks anywhere at intake or block halves.I have been through all fuel hoses and vent hoses filter is clean.I have consulted Zamas website and read up on the technical aspects on this carb.This is making me crazy as I can't get it to work.I hate to admit defeat however I'm at a loss as what to do now.Any help would be greatly appreciated.Thanks in advance for all your expert help and advice.


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## geogrubb (Jul 28, 2006)

Although you stated you didn't have any leaks, you didn't state how you checked for them, so with that said, with the engine running spray some carb cleaner along all the mating surfaces and insulator block behind the carb and crankcase to see if the engine tempo changes, if it does, you have a leak. Have a good one. Geo


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## scotty088 (Jul 4, 2008)

*Zama carb making me crazy*

Sorry Geo,
I should have been more clear.I sprayed carb cleaner all around intake and halves of the block mating surfaces with no change in tempo.I have spent many hours and gone way back in this forum to find all the tricks.Thats why this is so frustrating.The RB series Zama carbs are of the rotay barrel design with many parts the standard diaphram carbs don't have.I have checked and double checked the technicals at the website to make sure this is assembled properly.Thanks again for your help...


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## 30yearTech (Sep 14, 2006)

There is likely a restriction in the circuit that feeds the main jet. Sometimes if you take the rotary valve out and with the carburetor completely disassembled you can back flush from the main jet in the throat of the carburetor back to the metering chamber with carburetor cleaner. As based upon your description, your not getting enough fuel to meter through the carburetor. Check the roller guide that the throttle valve rides on, sometimes they will wear down on one side and not allow the valve to lift enough as it rotates, this is what increases fuel flow when the throttle is opened.

Best of Luck...


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## scotty088 (Jul 4, 2008)

When I dissassembled the rotary valve assembly the o-ring and roller were missing.I figured this will be a easy fix.I ordered the o-ring with a carb kit included with the kit was a new roller.Installed per Zama service manual instructions.I agree with you 30 year as there must be some:thumbsup: restriction I guess all I can do is tear it down again and see if I missed something.These little 2 strokes can be very touchy and cause us old mechanics to loose our hair.Thanks for all your help


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