Hard starting Stihl fs85

EGo_SmAsH · Jun 5, 2012

My Fs85 "pro series" weed wacker starts great when cold, I choke it and pull the cord about 2 times, it sputters and then starts right up after I open the choke. However, when the engine is warm like after I've been using it for an hour or so and then shut it down, it's very hard to start. This has just been happening this spring, it's a 4 year old unit owned since new. I've never done anything to it in terms of maintenance except for a fuel filter last year. I just use it for my own property probably about an hour a week during the summer.

RandyBell · Jun 5, 2012

I have the opposite with my FS 55 When cold it is a bear to start then even warm can't even take the choke clear off. I can't get enough adjustment on the carb to compensate. I am begining to think the carb is going to need to be rebuilt.

moship · Jun 5, 2012

I am probably stating the obvious, but can you post what all you've tried when 1st trying to restart after a hot condition? Example: Throttle closed, No Choke without prime; Throttle closed, No choke with prime; Throttle closed, Choke without prime and all the other combinations possible conditions.

Is the fuel fresh (less than a month old)? Do you store it without fuel and the carb purged by restarting after draining the fuel from the tank?

Although it is not the same engine manufacture/type I have an old McCulloch 3227HD trimmer that is impossible to start under the hot conditions you have stated. It has led me to purchase a new Stihl FS130 this past weekend, so I'm interested to learn of a solution in the event it is needed on the new trimmer

Have you pulled the spark plug after trying to restart to see if dry or wet?
There are a number of good videos on the web describing the basic trouble shooting points plus a host of Stihl dedicated ones for hard starting conditions.

Baby Grand · Jun 6, 2012

Are you using Stabil or similar fuel treatment? It transformed my 20 YO FS62 from a cranky old cussbucket into a reliable performer that cold starts on the 2nd to 3rd tug and hot starts on the first pull. Did wonders for my attitude, too.

EGo_SmAsH · Jun 6, 2012

Thanks for responses. I haven't done anything to try to fix this yet, thought I'd ask here first. To describe how I start it when it's hot, I usually just lock the throttle wide open and pull the cord and it has always started perfectly until recently. The fuel is high-test mixed 50:1 and is fresh. I don't use stabil because I always have fresh fuel around. If I don't use the weed wacker for a while (winter) I will drain the tank and run it out of fuel. Thanks

DieselMonk · Jun 6, 2012

My 6 year old FS-110 gave me first time trouble this year. Hard starting and running ******. So I took the valve cover off and set the valves, which were not much off. Took the air filter off the carb, started it give her full throttle and dumped Seafom in it until the engine quit. Did that 3 times, mixed a batch of fresh fuel with another little dose of seafoam, put her back together and she is running again like new.

newbury · Jun 6, 2012

First of all another vote for Seafoam.

Have you replaced the fuel lines?

Today's ethanol mixed gas rots the fuel lines.

Also see if it does the same with store bought pre-mix.

raptor749 · Jun 6, 2012

Got a fs85pro for free , would not run worth a c*** ,went to get a carb kit and it was $16.00 and new carb was only $34.00. Got the new carb and it runs like new :thumbsup: Friend that gave it to me had another doing the same thing , new carb fixed it too. Hope this helps..

:thumbsup:

MissouriSprayer · Jun 6, 2012

Fresh gas can still be garbage. They add the ethonol on delivery and the percent can be off substantially. Always add Stabil and many issues can be avoided

jim_wilson · Jun 6, 2012

EGo_SmAsH said:
My Fs85 "pro series" weed wacker starts great when cold, I choke it and pull the cord about 2 times, it sputters and then starts right up after I open the choke. However, when the engine is warm like after I've been using it for an hour or so and then shut it down, it's very hard to start. This has just been happening this spring, it's a 4 year old unit owned since new. I've never done anything to it in terms of maintenance except for a fuel filter last year. I just use it for my own property probably about an hour a week during the summer.

I just had a similar problem this year when I brought out my Stihl weed whacker to take out the jungle that is my backyard.

The thing would start a little bit hard and then run ok - but after maybe half hour or so it would just start dying.

Not having the time to screw with it I dropped it off at the dealer. It took them a few days to get to it. But they found that it needed the valves adjusted and just a carb clean. I got it back Saturday and it's back to working great now.

Only cost like $48.00

I had pretty much treated mine the same way you have treated yours. I've probably had the Stihl for 4 or 5 years now.