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Discussion Starter #1
I bought a Stihl fs85r trimmer on Craigslist. Started well when I bought it but some hesitation on pulling throttle. Brought it home, messed around with the throttle settings, put my gas in it and trouble ever since. I used it twice but most of the time it refuses to start. It does start when I put Seafoam into the carb but does not continue to run.

Question is, does the oil go bad? I used new ethanol free gas but the oil I had was a year old.

I know the carb is the other option but the Zama C1q-S28 model on this thing is $50, more than I am eager to spend.

I took the carb apart once and sprayed WD-40 through the holes and put it back together with the old gaskets. Was that stupid? I obviously don't have much experience with these things but I think I could install another carb if I had one. I am not sure how hard it is for a novice to rebuild a carb or if that is a better idea.

Any help is appreciated.
 

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Hello and welcome to Hobby Talk.The oil isn't causing your problem if it was mixed in just purchased gas.Fresh fuel is essential,and adding stabilizer at time of purchase will help maintain the octane.Cleaning the carb and using the old diaphragms wasn't stupid,it was just a waste of time and a learning experience.Below are links that will give you confidence if you attempt to rebuild the carb yourself.The Zama diaphragm and gasket kit for the C1Q-S28S carb is part number GND-28 and available at most small engine parts suppliers or on line.If the diaphragms are stiff from age and ethanol,the fuel lines should be checked for cracks and probably be replaced also.Hope this helps.

http://www.zamacarb.com/pdfs/TechGuide_2007.pdf

http://www.zamacarb.com/tipspage.html
 

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IMHO, you have purchased one of the best work horse trimmers ever so don't give up on it too soon. Have a good one. Geo
 

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Discussion Starter #4
Thanks for the support. The Zama technical guide looks amazing, I will certainly check that out. I am in a bind because my yard looks pretty bad and I don't have time to go wrong on a rebuild. I may just buy a new carb and possibly fuel lines and then play around with the old one. If that does not work I will let you know. Thanks again.
 

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basics also

dont forget to check the fuel filter. take it out, put the gas line back in and try to start. if much better, prob solved. remember to install a new filter. good luck.
 

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Discussion Starter #7
Update: I installed a new carb and the trimmer runs great, but it still starts harder than I wish it would. At first it only started when I poured carb cleaner into the carb. Now it starts without that but still takes many pulls.

Also, I noticed there is fuel seeping out of somewhere-- the top of the tank is wet and the floor is wet. I think it was happening before I changed the carb. Not sure if it is siphoning out of the tank or what?

Good idea on the fuel filter. I haven't figured out how to get those lines out of the tank. Do they just pull out and snap back in? I do not have the right screwdriver to take the tank off so it's harder to access the lines.

Thanks for your help everybody.
 

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The fuel may be seeping out of the holes in the tank that the fuel lines go in. The starting issue even with the new carb may be due to low compression.
 

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You can check the compression by laying the trimmer on the floor and grasping the starter handle and lifting the trimmer to waist height.If it stays on the floor or drops with little resitance it dosen't have adequete compression.
The next thing I would check would be the fuel line,especially considering the fuel leak.It is easily changed,just locate the hose with the filter on the end,remove the filter and pull the hose out.If I remember right the FS85 uses a straight hose(not molded)which slips through a grommet in the tank.If this is the case you can replace the original hose with Tygon available at small engine shops(just take your old hose to match up).To install cut the end of the hose at an angle,apply a little oil and push through the grommet in tank,pull through the fuel cap opening,cut off straight and reinstall the fuel filter.
I would also check the choke mechanism to be sure it is working properly.
Hope you get it going,this is a good model Stihl trimmer.
Don
P.S.The reason I call the fuel line a hose is thats what Stihl calls it.
 

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Discussion Starter #10
Don L: Thanks for the info. I will look at the fuel line. I was a little apprehensive to mess with the fuel hose because I wasn't sure how to do it but it seems fairly straightforward. My tank does have the grommet so I will do it as you suggest.

The trimmer has been starting easier lately; I think I am figuring out where to set the choke and the throttle to get it going. I think the compression is good but I will do the compression check.

Rentahusband: What would cause the fuel to seep out of the holes where the lines go in? That thought crossed my mind but I am not sure what to do about it, unless it is a faulty fuel line contributing.

Thanks again for all the help.
 

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The fuel lines harden over time and can loose their seal with the tank. Just replace the line. I use the Tygon fuel lines. Should be available at an auto parts place.
 
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