Chainsaw Repair

Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Stihl => Topic started by: 660magnum on November 23, 2013, 11:05:38 pm

Title: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on November 23, 2013, 11:05:38 pm
The 4140 family of yard tools include three different curved shaft weed whackers as well as "D" handle and bike handle straight shaft trimmers. This goes on to the edger, tiller, and Combi models. They are considered to be part-time home owner tools.

I acquired from Craig's list a few years ago a nice hardly used none running straight FS-55 bike handle bar weed whacker. About six month's later I got a FS-45 with the curved shaft. The FS-45 ran fine but had more sun exposure and use than the 55. These are 27.2 ci two strokes with a regular muffler. This type power head is on its way out for the FS-56 (4125) series or the four strokes.

Stihl FS 45  - Notice the power head is the same as on the FS 55R
(http://img.photobucket.com/albums/v11/jamesirl/CorpMain-2.png) (http://smg.photobucket.com/user/jamesirl/media/CorpMain-2.png.html)

All the FS-55 needed was a new carb and some string and then it was just like new.  I soon discovered that I didn't like either one. They ran OK and didn't break down but the FS-45 was too small for me and the FS-55 was too bulky for my needs. The FS-55 may have been OK if I had high weeds and used a saw blade but that was not my need.

Stihl FS 55
(http://img.photobucket.com/albums/v11/jamesirl/fs55-4.jpg) (http://smg.photobucket.com/user/jamesirl/media/fs55-4.jpg.html)

What got me to discover that I didn't like the Stihls was that I came across a SRM 2100, 21cc Echo straight shaft and then another SRM 2400, 24cc one. These were great for my yard and in fact I also have a hedge cutter, blower, and tiller. The Stihl FS-55R is just like using one of the Echo trimmers.

Looking on Ebay the individual parts to convert either weed whacker to a FS-55R were too expensive and it would be cheaper to buy a FS-55R D-handle type and use what I had for spares? Keeping a eye on Ebay all summer is that you never see a tube & liner for the curved shaft or one piece straight shaft trimmers and if you do, it is better to buy new.

Stihl FS 55R
(http://img.photobucket.com/albums/v11/jamesirl/CorpMain-1.png) (http://smg.photobucket.com/user/jamesirl/media/CorpMain-1.png.html)

Well, that's what I did. I bought a complete ratty FS-55R for the price of a gearbox and shield. I used the FS-55R straight tube, handle, FS-55R label, and gear head assembly on my FS-45 and then had at least one nice FS-55R for use around the house and it works good but I suspect the liner in the tube may be a little worn so down the road I may get one of those from the dealer. The liners are inexpensive.

That has created a CAD type addiction situation and I came across a set of covers for a FS45C that were real nice for $19 including shipping and used them on the bike handle FS-55 to make a FS-55R "D" handle out of it. I found a FS-55R shield and D-Handle on the cheap. But the saga goes on. The gear head on the junk FS-55R I bought was from a FS-90 and I like it better than the FS-55 style gear head. So I bought another genuine Stihl used FS-90 gear head to go on the FS-55 that I already had. When buying these parts you have to be patient for a cheaper one to come along. The actual drive shaft in these is a flex one instead of a solid one. I don't know if that is good or bad as far as my needs go? Might try a rigid shaft sometime in the future but not sure which trimmers have rigid shafts? You have to be careful as the Chinese have jumped on the band wagon and sell parts for these too.

Stihl FS 90R - Notice the different gear head from the one on the FS 55
(http://img.photobucket.com/albums/v11/jamesirl/CorpMain-3.png) (http://smg.photobucket.com/user/jamesirl/media/CorpMain-3.png.html)

So, soon, I'll have a pair of FS-55R string trimmers.

Stihl is rather secretive about their 4mix trimmers (Which ones are 4mix?). I get the idea that they are great except expensive when new but if one starts to give trouble, you have a can of worms on your hands?
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: Cut4fun . on November 23, 2013, 11:49:03 pm
Talk about carb problems. Cheaper to buy new carb $20-$30  carb and good for a long time.  I have a bunch of used dead 45 55 carbs here.
 Hate working on my friends 45.   I did figure one out and rebuilt it.  Sometimes it would act squirrely but works.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on November 24, 2013, 02:38:41 am
The original Zama carb on the FS-55 had some white corrosion inside the metering valve chamber, otherwise was clean as could be. The HS worked fine but there was no fuel on the LS. I ran wires through the three holes that go into the venturi and took the LS needle out and run wires in there and through the hole in the metering chamber floor that feeds the LS. But still no LS fuel.

So I had to pay like $29 total for a new carb at the Kubota (Stihl) store nearest the house. It worked perfect without adjustment.

(http://www.rcuniverse.com/forum/attachment.php?attachmentid=1941711&stc=1&d=1385280949)
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: Cut4fun . on November 24, 2013, 06:04:19 pm
Jim     Whats the story with the smoking dog. Curiosity is killing me and I'm laughing every time I see it.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on November 24, 2013, 06:21:09 pm
It is actually a You Tube anti smoking thing? But someone made this one into a Gif. It is too long to upload here so I linked it from one of my posts in another forum. I just thought it was cool. It is Photo Shopped or something for animals like dogs and cats don't like the smoke?

Here is the original maybe with the cigarette cough and the whole bit? Seen several different versions made into ads.

http://www.youtube.com/watch?v=IKbxMIWCto0
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: Cut4fun . on November 24, 2013, 06:28:27 pm
LOL
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on November 24, 2013, 06:32:20 pm
Never smoked myself
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: Cut4fun . on November 24, 2013, 06:37:42 pm
I did when I drank in the Military first couple years.   Some in Jr High too, but not high school.    Dont know why though.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: RoyM on November 24, 2013, 08:06:12 pm
I had an FS-45 but never really liked it. Too noisy and too much vibration to suit me. My current Echo GT-200 is a treat to use.
The FS-55 and FS-90 use the flexible shaft. The 55 can be fitted with a weed blade as well as the 80 tooth brush blade although Stihl discourages the latter. The four mix FS-90 does not accept a blade, it is a commercial grass/weed trimmer.
I'm old school, don't like the four stroke hand helds at all. They have great torque but are heavier and too complex, anything internal fails it goes to the scrap pile. They are not economical to rebuild. I am going to keep my 2 strokes going as long as I can.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on November 24, 2013, 08:10:20 pm
+1
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: Old Iron Logging on November 24, 2013, 08:37:03 pm
I had an FS-45 but never really liked it. Too noisy and too much vibration to suit me. My current Echo GT-200 is a treat to use.
The FS-55 and FS-90 use the flexible shaft. The 55 can be fitted with a weed blade as well as the 80 tooth brush blade although Stihl discourages the latter. The four mix FS-90 does not accept a blade, it is a commercial grass/weed trimmer.
I'm old school, don't like the four stroke hand helds at all. They have great torque but are heavier and too complex, anything internal fails it goes to the scrap pile. They are not economical to rebuild. I am going to keep my 2 strokes going as long as I can.

FS55 has a cable shaft but the FS90 has a steel shaft. The 90 thru 130 have the same shaft. As for blades all are recommended and used on the 55/56 and up by Stihl. Cable in 55/56 has a lifetime warranty.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: jmester on November 24, 2013, 08:40:31 pm
I have a 4 mix Fs 110. That has been a very good trimmer, a lot of landscapers around here use the 4 mix with few problems except for carbs and lines. Really the only thing to worry about with them is carbon build up around the valves that will not let them seal on compression. And the cam lobes will wear down and cause some fits. They make great low end power. I feel the Fs 80 regular 2 stroke was the best from back in my landscaper days.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on November 24, 2013, 08:44:47 pm
I had an FS-45 but never really liked it. Too noisy and too much vibration to suit me. My current Echo GT-200 is a treat to use.
The FS-55 and FS-90 use the flexible shaft. The 55 can be fitted with a weed blade as well as the 80 tooth brush blade although Stihl discourages the latter. The four mix FS-90 does not accept a blade, it is a commercial grass/weed trimmer.
I'm old school, don't like the four stroke hand helds at all. They have great torque but are heavier and too complex, anything internal fails it goes to the scrap pile. They are not economical to rebuild. I am going to keep my 2 strokes going as long as I can.

FS55 has a cable shaft but the FS90 has a steel shaft. The 90 thru 130 have the same shaft. As for blades all are recommended and used on the 55/56 and up by Stihl. Cable in 55/56 has a lifetime warranty.

Good to know.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: Old Iron Logging on November 24, 2013, 09:01:24 pm
Stihl does discourage blades on the R models, unless a barrier bar is added.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: Old Iron Logging on November 24, 2013, 09:07:33 pm
There is a new 24cc lightweight 2 stroke straight shaft trimmer coming in the spring. Can't remember if the FS85 tag was revived. Saw the trimmer in late summer. Really light.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on November 24, 2013, 09:31:36 pm
The guy in Greece has a pop up piston for the 27cc engine. It is 34mm and I think made for the Zenoah G26 power head? I think it is made by Chung Yang of Korea?

http://www.ebay.com/itm/Piston-Kit-fit-STIHL-BG-45-BG-46-BG-55-FS-55-KM-55-MM-55-34mm-Kolben-/171152677416?pt=LH_DefaultDomain_0&hash=item27d97e9a28
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on December 05, 2013, 08:34:24 pm
I have one Stihl Franken Trimmer ready for next summer as mentioned in the first post. At a distance it is a Stihl 55R. It has a 4140 27.2cc power head, FS 45 covers and FS 90-130 tube/gear head/guard.

I now have my standard Stihl FS 55 on the bench with all the parts on hand to make it a "R" style  like I want too. I just need to cross breed it with the detail parts.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on December 20, 2013, 11:44:02 pm
I finished making my FS-55 bike handle weed whacker into a FS-55R loop (D) handle style weed whacker. I removed the FS-55 power head and then removed the FS-55 covers from the Power head. I then installed a set of FS-45 covers on the power head. What a chore. The throttle cable routing, throttle trigger interlock, and return springs on the lock and the trigger gave a lot of trouble. Everything had to be just right or none of it would work. I then installed the tube on the power head and then a FS-90R gear head and shield, then the 25-2 bump head. Everything seems to work. I'll have to run it tomorrow.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on December 21, 2013, 12:14:05 am
One secret when removing the top cover from a 4140 style power head is that you can loosen (but not remove) the starter housing to get to the bolt on one side that holds the top and bottom covers together. Otherwise you cannot get a T-27 Torx on the bolt. If you completely remove the starter cover, then the tank is loose etc and one thing leads to another. The tank is held by rubber bushings between the bottom cover and the starter housing.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on December 21, 2013, 09:37:45 am
The Stihl FS-55R started up second pull and ran fine without any adjustment this morning in the drizzling rain. So I'm declaring it finished.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on May 08, 2014, 08:26:14 pm
Solid shaft for my FS55R straight shaft trimmer???

The FS55R comes with a flexible shaft from the factory. There's nothing wrong with the flex shaft and it normally last many years in regular weed whacker duty.

I had been keeping a eye on Ebay for maybe a year for conversion of a FS45 and FS55 to a FS55R setup? (Now complete)

The tubes for the trimmers are typically hard to come by from used sources because they get bent.

There's a lot of unknowns in this swap. Will the solid shaft fit in the flex shaft tube assembly? Are the ends the same?

WELL, The FS90 tube/shaft assembly is 3 3/4" longer than the FS55R assembly, so you cannot use a FS90 solid steel shaft inside a FS55 tube assembly because it is too long.

The good news is that you can use the whole FS90R assembly in your FS55R. They are the same diameter. All the parts, gear head, and "D" handle fit either the FS90R or the FS55R.

The gear heads are a different model between the two trimmers but actually, the heads will interchange. The FS55 gear head has a single retaining clamp screw whereas the
FS90 has two.

There's another problem with using the FS90R tube/shaft assembly in a FS55R power head and that is the 1/4" retaining screw hole is in the wrong place. The hole needs to be 7/16" from the end when using the covers for FS55R.

I was lucky enough to find a new pair of FS90R tube/shaft assemblies from Fish > a member of this site.

My two FS55R's already had FS90R gear heads so the swap was straight forward and works great.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: Al Smith on May 08, 2014, 09:27:22 pm
As coincidence would have it I just last Sat bought a brand spanking new fs 40 .Rather unusual for me to buy any thing new but I lost my patience .Danged Echo gt 1100 had the coil go bad.

I just went ahead and got the blade head to start with .I hate string heads ,nothing but a pain in the butt .
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on May 08, 2014, 10:06:24 pm
I have a gaggle of Echo's old and new. I like the 2400 blower, 2100 hedge trimmer, 2100 & 2400 string trimmers, and the new rototiller all as original, that I have. I do not have any Echo saws but have a Echo 520 saw engine as a model airplane engine.

I really like the Stihl FS55R trimmers but two of mine are Franken Trimmers made from other models but to see them, they would be recognized as Stihl FS55R's. Just what I like to do.

I did a lot of this with model airplane engines also.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: tinkerswithengines on May 10, 2014, 09:46:41 pm
660 Magnum

Any suggestions on a replacement gear head or the whole shaft and head for on a FS 81 trimmer? The shaft is smaller than those used on the FS90's etc.
This old classic of mine (1991) is "Stihl"  ;D running strong. However, replacement gear heads and parts are now like hens teeth. Should the gears or bearings fail.........I hope I don't have to part with it.

Dave 
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on May 11, 2014, 02:08:31 am
660 Magnum

Any suggestions on a replacement gear head or the whole shaft and head for on a FS 81 trimmer? The shaft is smaller than those used on the FS90's etc.
This old classic of mine (1991) is "Stihl"  ;D running strong. However, replacement gear heads and parts are now like hens teeth. Should the gears or bearings fail.........I hope I don't have to part with it.

Dave 
I just don't have any experience with the FS-81

I spent several years with Homelites and McCullochs back in the 80's & 90's.

Then it was Echos and more recently Stihl FS-55R's

The Stihl's have been somewhat of a challenge because of the different sizes and types. I just hit it lucky and it took me a couple years to do that.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on May 12, 2014, 05:07:14 pm
I found a Stihl FS65 which appears to be a all metal old timer in the back corner of my barn. I think I have most of it if anyone has a need? It is not made like the present day trimmers. The tube is bent and the carb is missing!
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on May 12, 2014, 05:20:15 pm
Looking around in my barn I had a complete Stihl FS-45 curved shaft trimmer standing against the back wall of the barn. It was originally a shabby Ebay FS55R straight shaft trimmer that I had bought for parts and I used the FS55R shaft and cutter head parts from it on my FS45. So I had put the 45 curved shaft parts on the Ebay trimmer.

Thinking about that trimmer power head today, I had enough FS55R parts to make it a FS55R again. To my surprise, the trimmer started right up. But it doesn't idle right. I figure it was someone's frankentrimmer and they don't have the throttle cable and other throttle mechanism routed correctly? I'm out of time today but some other day, I'll take that area apart enough to look for problems? If that doesn't get the trigger working freely and solve the idle problem, I'm looking for a air leak. The starter cover is all busted up but it stihl functions to start the trimmer. I'll have to get a bare cover and transfer the starting mechanism over to it. The spark arrestor spud is missing from the muffler but does not make the trimmer too loud. The off-white cover is dirty but I'll get it cleaned up some after I get the other problems fixed. Now I need a Stihl FS55R name plate to go on the starter and it will be complete.

Some of Brazil's finest . . .
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on May 13, 2014, 07:23:51 pm
Worked on the FS55R Ebay ratty weed trimmer today. Killed two birds with one stone. One of the nuts holding the carb on was missing and the throttle cable length compensator was not in its pivot hole. Got a 5mm X .8 nut at the Stihl dealer down the street and I ordered one screw for the starter housing and one screw for the gas tank. I also ordered a bare starter cover.

I attached the carburetor correctly and everything ran fine.

I scraped the heavy black marks from the top and bottom off-white covers and sanded them down with some 320 wet or dry paper except for the "Stihl" label and the serial number label. The weed whacker looks pretty good setting on the ground. Soon as I make up the new starter, it will be a very respectable, completely standard as from the factory, Stihl FS55R.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: tinkerswithengines on May 14, 2014, 10:39:03 am
Your having way too much fun! ;D
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: Fish on May 14, 2014, 05:06:11 pm
Yeah, the fs65 is one of the old Japanese trimmers from the 70s-80s...
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: bloodontheice on May 15, 2014, 02:49:14 pm
We sold hundreds of FS55/45's over the years and besides the FS90's its been our best selling trimmer.

Seems like all the ever need is fuel lines and a carb. and the fuel lines seem to hold up better than the carbs.

Luckily they dropped the price of the FS56, it's strato replacement we were having a hard time moving them at
229$, now their 199$ for the spring and seem to be moving better.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on May 15, 2014, 05:22:29 pm
I was at the Stihl dealer about 3/4 mile North of my house day before yesterday and some guy was picking up a FS56R that he had bought earlier and they had run it etc for him.

I ordered some parts and got them in 2 days.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: H 2 H on May 15, 2014, 07:23:17 pm
When I bought my FS 45 everyone told me it was to small and wouldn't last a year for what I use it for; it's been three years and two spools of line working on the third spool and just keeps on going

(http://i59.photobucket.com/albums/g317/H2H_PHOTOS/MS%20250/DSC_5032_zps474bbc71.jpg)

(http://i59.photobucket.com/albums/g317/H2H_PHOTOS/MS%20250/DSC_5033_zpsdb0c2c08.jpg)

It sure doesn't look like this now :)
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on May 15, 2014, 08:18:56 pm
You got me with those pictures . . .  I was looking at those pictures and was thinking, for all the line he has used, the FS45 still looks new?

Then I read the caption under the last picture.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: H 2 H on May 15, 2014, 10:33:41 pm
You got me with those pictures . . .  I was looking at those pictures and was thinking, for all the line he has used, the FS45 still looks new?

Then I read the caption under the last picture.

:)

Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: brokenbudget on May 16, 2014, 09:23:02 am
the only problem I see on these is every once in a while the 'nut' that the trimmer head sits on. it and the little shaft is splined and after a bunch of hours they like to strip. I don't bother buying the whole new end. I just get everything lined up properly and drill a small hole all the way through and pin it. usually a shingle nail. I then peen each end down flat to the nut so the head still fits on proper. free, quick and stronger than what was there.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on May 16, 2014, 09:30:21 am
"Good Fix"
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: tinkerswithengines on May 16, 2014, 06:42:00 pm
That's not just a good fix....that's a GREAT fix! ;D

At the shop when one these 45's/46's curved shafts came in with that problem, it was always bad news for the customer. We ended up selling them a new trimmer or a complete new shaft assembly since Stihl will not offer a replacement ...at least here in the USA.

I do have two of the shafts in my shop that have the "loose" nuts. I had previously tried re-knurling them with a series of new and deeper knurling with a small sharp chisel. However, they never held up for very long. I had never gave it a thought to drill a hole through the nut and shaft :'(.

Well, when I get the time, I am going to attempt that operation but I think I will use a roll pin in place of a roofing nail.

One other problem with them is that the retaining ring at the end of the shaft will come off. Getting a new tight spring steel retainer of the right diameter wasn't always at hand and re-using the old one, if found seemed to not hold up very well. The bronze bushing, if still serviceable at the time of the mentioned repairs should be greased with a high temp grease.

Thanks for the tip! Learned something new today....now I can go to bed tonight a happy man! ;D

Dave
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: brokenbudget on May 16, 2014, 06:56:43 pm
tinker, I did try a roll pin the first time I did it. even with a proper sized pin for the hole, after a week it ended up working itself out and wearing through the plastic of the head, locking it in place. I've used the roofing nails in the past on other projects with nothing but good results and decided to try it here. the one good thing about peening both ends is that pin isn't going anywhere. the nail is soft enough to peen down nicely and strong enough to hold much more abuse than the knurled fit. :)
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: tinkerswithengines on May 16, 2014, 07:31:40 pm
OK...stands to reason.

Thanks again!

Dave
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on May 16, 2014, 09:09:23 pm
I never really used my FS45 that much as I liked my straight shaft Echos.

Now my FS45 has a FS90R straight shaft business end so I'll use it more. I did the ditch by the high way and around all the trees with it already this year.

The old FS45 curved assembly is standing in the corner waiting for me to put it in the barn. I'll have to look and see if it has been modified. I don't know just how much the trimmer was actually used but it was in the sun a lot for the covers are dull.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on May 20, 2014, 09:27:24 pm
I changed over the starter cover on the old parts FS55R I was playing with. I discovered that you can not install a old rewind spring in a 4140 series rewind housing. I bought a new rewind spring < $10 and it comes in a little plastic cup. You place this plastic cup / spring over the install position in the starter cover and push the new spring into place in the starter cover. Slick as can be. I then wound the old spring into this little cup (no problem) for the next time I need a starter spring. I put in a new 3mm starter cord, started up the FS55R and did the ditch out by the road again.

Found a few mistakes in the Service manual - one being no mention of the rewind spring cup for re-winding the spring. You cannot get a new cup anyway without buying a new spring.

Then there is a wrong screw part number listed to hold the gas tank on. The correct screw is listed there as well.

Another being the typical Stihl retainer spring/pawl guide for the starter pulley is shown aimed in the wrong direction in the service manual.  Installed as shown in the service manual and the pawl will not come out when you pull on the handle. The way shown in the IPL is the correct way.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on May 23, 2014, 07:54:50 pm
This one Stihl FS55R had been running "funny" with the mixture being unstable. I suspected a old stiff metering valve diaphragm

Monday of last week I went to start this Stihl FS55R weed whacker. With the choke on and second pull it sputtered. Flipped the choke off and from then on it was flooded. Then I noticed gas pouring out the air filter. So the metering valve is stuck open?

I was going to get a diaphragm kit for it but worked on a couple others instead.

I got to thinking that I had a bad one of these carbs that I had put new diaphragms in several years ago so I found it and stole the metering valve diaphragm. I didn't take the carb  off the FS55R, I just changed the metering diaphragm with the carburetor mounted on the weed whacker. The prize FS55R started right up but soon I noticed the clutch wouldn't release. It's a chore to get to the clutch! I shut the Stihl down and turned the cutter head. It wasn't stuck so bad that it would turn the engine through compression. I turned the cutter the other way and the piece of sand, or whatever it was, fell out and the clutch worked perfect again. Thank goodness.

I then did my weed whacking, cleaned it up and put everything away.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on May 23, 2014, 08:46:00 pm
I was doing the ditch out by the road on Wednesday with one of my all stock Stihl FS55R's and when I got done, the neighbor across the street came over. He was talking how he didn't really care for his Stihl FS45 curved shaft whacker. I showed him my former FS45 that I put the FS90R assembly on. First thing he said was that it was too heavy.

That assembly weighs close to one pound more than the FS55R assembly. A complete FS90R Four Mix weighs more than two pounds more than a complete FS55R. So keep that in mind.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 3000 FPS on August 23, 2014, 12:51:13 am
Thought I would add this here.
I worked on a Stihl weed wacker today.   It is a FS100RX.   This trimmer is a 4 stroke engine with valves, rocker arms, and push rods, but it runs on 2cycle fuel and it has no crankcase for holding oil.   When I got it started it sounds like a 4 stroke engine.   
My big question is does this engine have transfers that feed up into the intake valve to direct the fuel charge, and what other 2 cycle characteristics does this engine design use.   Like how do they oil the top end of the valve train. 
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on August 23, 2014, 01:38:05 am
Look in your SBC mail for the 4180 service manual.

The thing oils by blow by and the intake runner is like a B&S 4S with oil in the crankcase?
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on August 23, 2014, 01:47:51 am
The four stroke Stihls are rather popular in this part of the USA. Two neighbors have them and the other has a Stihl FS45. And from the early part of this thread, I have a gaggle of FS55's

Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 3000 FPS on August 23, 2014, 01:48:56 am
Very good Jim thanks.   Looks like some good reading I appreciate it.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 3000 FPS on August 23, 2014, 01:50:41 am
This FS 100 is not the first 4 stroke weed wacker I have come across but it is the first one I have worked on with no oil in the crankcase.
Title: Re: Stihl 4140 family Weed Whackers FS-45,55, etc
Post by: 660magnum on August 23, 2014, 03:21:22 am
The owner's manual which Stihl calls the Instruction manual is downloadable from Stihl

It takes on the everyday service and operation including valve adjustment.

The cutting head is the 27-2 the same as the FS55R or you can use the blades.

The head ratio is the same as the FS55R but none of the gearbox parts interchange though the guard is the same.

The diameter of the tube and the square connectors on the flex and solid shafts are the same but the lengths are 3" different.

The retaining hole in the tube for the motor end is 90 degrees out of phase between the FS55 types and the FS90 types.