Hard starting Stihl fs85

[EGo_SmAsH]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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.

 

[whistlepig]

I have owned Stihl weed eaters for many years. Even before ethanol the plastics in the fuel system had a shelf life. The filter has to be replaced time to time. The small fuel line from the filter does collapse. And the the primer bulb can start leaking air. This is mostly the problems I have had starting Stihl weed eaters.

 

[Treemonkey1000]

If he has been running it for an hour then you have used up most of the gas in the fuel lines. I am thinking the heat is expanding the the cylinder/ carb gasket and leaning it out too much? Or the fuel line is warmed up and letting air get sucked in the line a little.

 

[EGo_SmAsH]

Ok, I'll have some time thiss weekend to try to fix this. Bad gas is not the problem, I use the same mix in my saws and they run fine, also the weed wacker runs fine too, aside from the hot starting problem. I have noticed that the outside of the carb is wet/dirty from a fuel leak somewhere. I think I will stop by the dealer and pick up a carb kit and a new fuel line. Anything else?? Is a primer bulb part of the rebuild kit?

Thanks

 

[Treemonkey1000]

A buddy of mine just gave me an FS85 yesterday. Nice looking weedeater. One of his employees didn't put it on the truck very well and it fell off and busted the fuel tank. I am going to see if I can epoxy it first. I looked on Ebay and can get a tank for $20 and carb kits for $9. Not bad. So it won't take much to fix it. He gave me a Homelite backpack blower that needs a fuel filter and gas line thru the tank so that will be an easy fix. Plus a couple of chainsaws than need pullcords.. He was going to throw the stuff in the dump.. Guess what I will be doing out in the shop this weekend?

 

[Baby Grand]

A buddy of mine just gave me an FS85 yesterday. Nice looking weedeater. One of his employees didn't put it on the truck very well and it fell off and busted the fuel tank. I am going to see if I can epoxy it first. I looked on Ebay and can get a tank for $20 and carb kits for $9. Not bad. So it won't take much to fix it. He gave me a Homelite backpack blower that needs a fuel filter and gas line thru the tank so that will be an easy fix. Plus a couple of chainsaws than need pullcords.. He was going to throw the stuff in the dump.. Guess what I will be doing out in the shop this weekend?

Saving the planet and keeping our landfills open, one landscape tool at a time! What could be more American?

 

[Treemonkey1000]

Saving the planet and keeping our landfills open, one landscape tool at a time! What could be more American?

Kind of my thought as well. Shoot if Ebay weren't such a hassle I would toss them on there as parts machines for someone else. Fun to tinker with this stuff. I can put them in my garage sale after I get them running or list them on Craigslist.

 

[EGo_SmAsH]

Just to update, I rebuilt the carb and replaced the fuel lines and filter. It starts a little better now when cold and runs much better in terms of throttle response. As for the hot start problem, I wont know untill I really get her hot.

 

[Treemonkey1000]

Just to update, I rebuilt the carb and replaced the fuel lines and filter. It starts a little better now when cold and runs much better in terms of throttle response. As for the hot start problem, I wont know untill I really get her hot.

Cool stuff. I am hoping that the old gas line was getting soft and letting in air. So far I have fixed the backpack blower with new fuel lines from the bulb to the tank and new fuel filter along with the gas line to the carb. One of the small saws there is no spark so that may be a condenser or bad plug. Still haven't played with the string trimmer.