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Zama on Echo blower that is sending raw fuel back out from throat of carb. Have rebuilt carb but still running extremely rich. Checked spark arrester in exhaust and it is clean.

When you rebuilt carb did you replace gaskets? If so installed correctly. I would take the muffler off and inspect the exhaust port for carbon build up. If none your problem lies within your carb probably the air channels clogged up

Yep new gaskets and diaphragms. No carbon in exhaust port. Cleaned carb very well with brake cleaner and ran wire through accessible holes. Could bad piston rings cause symptoms???

Thanks

Just a couple of things,

If it is "running rich" and the excess fuel is dumping back out of the intake side then I would guess that the problem lies in the carburetor. Zama Rotary? RB-XX?

When the muffler was off, did you visualize the piston and rings via the exhaust port in the cylinder? any scoring or metal transfer?

Timing slightly off? causing the engine to be way less efficient? Most of the Echo stuff uses the plastic flywheel with the key machined into the metal in the center. Is it partially sheared?

Lastly: Did you run it with the muffler loose or off? If not, I'd try that first. Some of the newer Echo stuff has a converter in the muffler that can cause a ton of problems. These engines are designed to run with a very specific "air pulse" going threw and even back after combustion. I have had my hands on several Pb-251 blowers that have had problems with the converters.

Just my opinions. Take what you want and leave the rest.

Thanks

I had the same problem with my ECHO GT 200R string trimmer after I redid the entire fuel system. What happened was when I installed the new grommet the new return line fro the primer base ( the clear one) is very soft compared to the old one which got hard because of age. When I pushed it through the new grommet pinched it enough so fuel could,nt return to the tank, thus makeing it run rich and raw fuel coming out the breather. So I pulled it up a bit recut to length and now runs perfect again. I hope this works for ya.

Thanks for info.. I'll check that out

What is the model number of your trimmer?

Echo PB602 blower

If you need a new carburetor, it can be bought for $32 here. Sorry I couldn't find it cheaper, but you have a high end machine, so parts will cost more than if it were an MTD.

Thanks for that info