FS 90R PROBLEM SOLVED

Boobala

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Feb 15, 2015
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Hoping this post may be helpful to the "next-guy" .... I just spent 3 days (on & off) trying to fix my Stihl Trimmer, 6 yrs old never any issues, routine maintenance, filters, valve adjustment, added a Speed-Feed Head then last week it began acting up like it was starving for fuel, but the tank was at least half full, then it would clear-up for a half-hour or so, then start missing again, I NEVER had the carb pulled apart, except to replace a primer bulb 1 time. So........ I figured I better rebuild the carb, took the carb apart and it was really clean, so I cleaned everything up, put it back together with new gaskets and diaphragms, removed fuel-lines from the carb, and blew them out, replaced the filter, after cleaning the tank with fresh-gas wash-out, blew it all clean and dry, reassembled everything lookin great !! was hard to start, mixture screws ( I removed to clean out ports ) were set as before HMmmmm ?? FINALLY, after much pulling and using choke it started,.. wound right up then acted as if it was running out of gas, so I figured I must have somehow got a speck of dirt in the carb, pulled it off and went through it again, same results, OK this carb has a bug, and I have a LOT of weed-whippin to do, ... went to dealer bought a new STIHL OEM carb $46.00 .... slapped it on and it started right up, shut it off went to my trimming job and no start !! .. #@&%$##@%$# NOW WHAT ?? went through my Stihl factory manual, was able to perform vacuum test and it checked good, could NOT do the pressure tests, ( no special tool ) cleaned the NEW carb.... still no go.... decided carb HAD to be OK so the tank MIGHT be the problem, went to shop got new fuel "connector" ( grommet) with O-ring installed, that's the way it comes, a new tank-vent assy. and a new gas cap, thats the only way you can get the o-ring for it ! AND NEW fuel lines, getting the fuel connector out was a trick without damaging anything, a flat screwdriver blade and patience ( squirted some WD-40 on top of fittings to help lube them a bit ) the vent was a real &%$##@%$#@ the top half popped off and diggin out the bottom half was hell but again patience prevailed ... NO-DAMAGE !! once I got the fittings out the problem was quite obvious...... put it back together again, runnin like a scalded arse ape again, OH JOY !! what I'm gonna do is SCHITT-CAN that Stihl fuel pick-up hose and filter and just put on a tygon hose with a WEIGHTED type filter as in my Shindaiwa's..... my own oversight, but I sure as hell wont forget this lesson, and how to avoid it happening again, OH Yeah, the connector comes with that POS fuel pick-up hose.. only way you can get either piece... such a GREAT machine to have a POS fuel line design .. enclosed pics, I guess the Ethanol and floppin around all that time got to it ..........

DSCN2923.jpg..DSCN2925.jpg..DSCN2930.jpg..DSCN2956.jpg..DSCN2957.jpg..DSCN2958.jpg..DSCN2959.jpg..DSCN2960.jpg

If you have to do this job, be sure to spray the fittings with some type of lubricant to ease removal, when installing be sure to use a light film of vaseline or oil on the o-rings BEFORE trying to install the fittings, the vent only goes down so far.. see pics, but connector seats when "tab" sits on the lip. SO.. if you have an FS 90R ...... you been notified !
 
Last edited:

bertsmobile1

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Nov 29, 2014
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This is why I send people to Joe Pace's You tube channel when they have hand held problems.
He was the only person out there showing the proper proceedures, start from the beginning, the fuel tank & lines before you touch the carb.
I have fixed so many "unfixable" hand helds by following that method.
And apart from saving money by not pulling apart a carb that is working perfectly well it takes about 2 minutes to check the fuel tank & lines.

As for lubing them, WD 40 and similar products actually make it harder, Silicon spray is the go and usually it is easier to remove the fuel tank while leaving the carb in place on trimmers.
Finally all hand held filters are weighted, the Walbros are made from zinc so they sink the Tilloson ones have a plug of nickel in the end and the porex ones are heavy enough in themselves being porclean
 
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