Fs80

[stihltech]

Calling all Stihl Techs:
There is a common problem on the newer style FS80 brushcutters. Seems to get worse with age.
When you first hit the throttle, the machine shakes very hard, stops as soon as the revs start up. No problem when revved up.
I have started at the cutting attachment and worked up. Got as far as the clutch at this point. Have tried different carburetors, sparkplugs, carb settings.

I also never seem to get a straight answer from Stihl, but have not talked to Ben Crago yet. The problem with working after 5PM.

So, anybody else seen this problem?

 

[Lakeside53]

I got your PM a few days ago... it's to early for us to even have weedeater in for service this year.. but they'll decend on us in the nest few weeks..I. 'll ask the other guys Thursday.

My recollecton from last year was that the bearing in the housing below the clutch was a problem... but I'm not sure it's related to what you are experiencing. We've sold boat loads of FS80, and have had few problems (other than stale gas/carb, and the occasional coil). Stopped carrying them them last year when the FS90 came out.


Does it go away if you replace the flex shaft?

 

[PES+]

I will wait for the Stihl expert before I respond

To save arguments

Yes I have seen a lot of this and it is partly inherent on a cable drive trimmer.

 

[stihltech]

cable

Sounds like I need to swap in a solid shaft next.

 

[PES+]

See what Stihl NE has for suggestions then I will walk through it with you later.

I would rather not have you put in the middle of a repair dispute

Check the gear case closely and make sure it has the right grease and is not overfilled or contaminated.

Also check the clutch closely for even engagement of the shoes and for any uneven wear in the drum and the clutch housing and bearing for ANY side play or too much axial movement

 

[Trigger-Time]

My FS80 dose it also..........but its the only one I have run.
I thought it was just the nature of it. I'm not at home but
I think it has a MD of 1999. I bought it in 2001.

 

[stihltech]

news

Well, NE Stihl called back. Seems there is a different shaft to motor housing with more reinforcements. I will check it out later tomorrow.

 

[Lakeside53]

Yes... and the concensus in our shop here is they all do it, and do get worse with time. The culprit - assuming the clutch bearing, bearing mount and flex shaft is O.K. - mainly the plastic guides inside the tube get worn out. The solution if the customer complains too much - solid shaft.

 

[stihltech]

well IIIIII'lll be!

Would not have believed it if I had not tried it.
Seems there are a couple of AV couplings for this setup. One is just tapered from the shaft to the motor. The other has two reinforcement struts from the shaft to the stand on the bottom of the coupling.
I started the 80 that shook badly for reference, then switched the coupler. Shake 95 per cent eliminated!
NE Stihl did say that too large a diameter string or too long a string will make the problem worse.

 

[Cam501]

Yes... and the concensus in our shop here is they all do it, and do get worse with time. The culprit - assuming the clutch bearing, bearing mount and flex shaft is O.K. - mainly the plastic guides inside the tube get worn out. The solution if the customer complains too much - solid shaft.

We sell boatloads of 80's also with no major problems, heck, I think I have about 35 FS80R's in stock right now. It's a shame that they won't be around next year. They need to make a cable drive version of the 90 that's priced like the 80. Guys who don't ever use a metal blade won't pay 319 for a trimmer. But to get back on topic I agree this issue does get better when you put the solid shaft in it and basically turn you 80 into an 85.

 

[stihltech]

lots

We sold many also. Only some of the pros complained about the vibration, no homeowners. I wonder if the 55 is supposed to take it's place? Does leave a big hole in the lineup. I see a price reduction in the works.
Maybe a FS 78 ( I don't think that was used yet).

 

[Jack_Shaft]

We killed a few FS80's when cutting trails for our snowmobile club last Spring. I have since purchased an FS500 and FS550 and solved that problem real quick.

However, they are expensive suckers.

 

[stihltech]

550

You trying to kill the volunteer workers?:jawdrop:
Saves taking a small saw with you.

I like the solid shafts for any serious work, but the flex shaft is just a few bucks cheaper........

 

[Timberhauler]

I have an FS85 trimmer I bought back in 99.It still runs great,but it's done the exact same thing you have mentioned since it was new..I really haven't paid it much attention until reading this thread and using it this weekend..I also have a FS250,and it doesn't do it.

 

[stihltech]

shake baby shake

Can't say I have seen a solid shaft do it. Don't have a poly cut head with the swinging plastic blades on it, do you.