Walbro carb problems..

[jhellwig]

It isn't on a chain saw but a stihl FS86 brush cutter.

I rebuilt the carb after it sat for 6 years and now it is giving me problems. I replaced every thing that the kit came with except some little tin plate that was painted red on the needle side. I also replace the fuel line and filter and cleaned the tank. I set the high and low screw to one turn out like the manual stated and attempted to start it. All it does is flood. I closed both screws completely until it actually started. I then cracked the L screw until it idled fairly well not more than a quarter turn. At this point I can only slowly throttle and when I let off it quits. It was leaking a lot of fuel out of the gasket on the diaphragm site. I took the diaphragm off and inspected it and reinstalled it and tightened the wee out of the screws. Now it will start but won't stay running for more than 15 seconds. I still can't set the screws where they are supposed to be without it flooding.

What did I do wrong???? I do have a parts breakdown and everything is where it should be.

 

[Four Paws]

What did I do wrong???? I do have a parts breakdown and everything is where it should be.

Well, if you checked and made sure your gaskets/diaphragms are in the proper order, then perhaps your needle and lever arm are set at the incorrect height. Also, did you completely disassemble the carb, remove the needles, etc. and clean all the passages with carb cleaner? Varnished gas can easily plug and/or restrict the flow through the small passages in a carburetor.

 

[jhellwig]

I did make sure that all the passages were open. I didn't change anything on the arm for the needle valve but I didn't verify its setting much less know how to do it. Any info?

 

[Lakeside53]

The top of the arm is level with the base of the metering chamber.. make sure your metering spring is located in the arm indent.

Sounds to me like your gaskets/diaphragms are in the wrong order... Check them against your ipl and note they reverse from the metering to pump sides.

Pressure test your carb - it should not leak with 10psi on on the fuel inlet side.

 

[daemon2525]

Try again

Take the thing apart again. Make sure that you clear EVERY hole with carb cleaner.

Then, when you go back together, make sure that the gaskets and diaphragms are in the correct positions.

On the meter side: the gasket is next to the carb body. (the big part)

On the fuel pump side: the gasket is next to the cover. (opposite the other)

Now, if it is flooding, it may be that the little metering needle is not seating correctly. You should be able to blow (with your mouth) into the fuel line (from the tank) and move the needle up and down, and tell that the thing is alternatly opening and closing.

 

[jhellwig]

I got it running like a champ now. All my gaskets were in the right place. I took it apart again. The lever on the needle valve is not level with the top of the carb but it is lower. Must be the way it should be. I took the needle valve out and blew through everything again. I must have had a stray piece of dirt somewhere. Everything is peachy now. I still don't understand why that would have made gas leak from the top gasket though.


Thankyou for the help everyone.

Now I just need a tach to fine tune it.

 

[Lakeside53]

Remember that with a trimmer it's important to get your string set to the correct length before tuning the H end. The string is the load. If you are unsure, just set it one turn out an forget it.