# Stihl FS130 Trimmer (4-Mix) with Extreme compression



## wrencher2b (Feb 19, 2005)

Hi All:

My Stihl FS Trimmer with it's 4-mix engine has become impossible to start, when cold. 

The pull-cord will come out about 8-10 inches, when attempting to start, using excessive pulling strength (in comparison to starting my other 2-stroke and 4-mix Stihl equipment. 

I've removed the spark plug, pulled the pull-cord and the engine turns over without resistance. No fuel-mix comes out of the cylinder, so there is not any fluid locking causing the problem.

In researching this problem, it appears that this model has an "automatic compression system" that reduces the compression system when starting. 

My question ... Is this "system" adjustable, repairable and/or replaceable?

Does anyone have a similar experience with the Stihl FS 130 (4-Mix)
and can help me get this trimmer back into action?

Many thanks,

Wrencher 2b


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## 30yearTech (Sep 14, 2006)

You might want to remove the valve cover and have a look at the valve operation. make sure both valves are opening and closing and check the valve lash. I am sure Paul can post the specs for your trimmer.


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## wrencher2b (Feb 19, 2005)

30yearTech:

Thank you for your input.

The problem doesn't appear to be in the valve operation. As noted in my original post, "I've removed the sparkplug, pulled the pull-cord and the engine turns over without resistance".

Wrencher 2b


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## 30yearTech (Sep 14, 2006)

wrencher2b said:


> 30yearTech:
> 
> Thank you for your input.
> 
> ...


Compression release is predicated on proper valve operation and clearances, so it's very much dependent on *proper* valve operation. If you have excess valve lash on the valve that is used to release compression, the compression release will not operate.


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## paulr44 (Oct 14, 2008)

You're experiencing a symptom we tell all customers about when purchasing a 4-mix powered unit. Or, at least we try to.

The 4-mix motors require periodic valve lash adjustment. They used to even give you (years ago) a feeler gauge and a rocker cover gasket with the owner's manual pack.

The intake cam lobe has the compression release on it, and when they get hard to pull over, the lash is excessive. Now, it could also be that if you're using a low-grade mix oil, or if it has a lot of hours on it, it could also have excessive carbon buildup in the combustion chamber. After setting the lash, if still hard to pull over you need STIHL or similar de-cabonizing fluid.

You need to visit your local STIHL dealer...purchase a 4180-xxx feeler gauge (standard ones don't fit unless you're willing to cut one with a sissors)(they're like $1), and always use a new 4180-xxx rocker cover gasket, as if the CC doesn't seal properly the fuel pump won't work.


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## paulr44 (Oct 14, 2008)

http://www.stihlusa.com/WebContent/...ls/STIHL-FS-130-Owners-Instruction-Manual.pdf

See pages 47 for spec. They used to tell you how to set it.
Remove the spark plug, and with the rocker cover off pull the engine over slowly. After watching the intake rocker (closest to the carb.) open and close, now look at the flywheel as you keep pulling slowly. There's an arrow on it. When that arrow aligns with the coil screw nearest the carb., stop...that's TDC on compression stroke, and the point at which to set the lash.


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## wrencher2b (Feb 19, 2005)

30yearTech:

Many thanks for coming back with your followup comments. 

What you say makes a lot of sense...I have [now] seen the light.

I'll do as you have suggested and post my results.

Thank you, again, for your diligence.

Wrencher2b


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## wrencher2b (Feb 19, 2005)

Paul44:

I've seen the error in my ways. Your detailed response to my post has helped make it clear to me the the repair path that I need to follow.

Thank you for sharing your knowledge and your time taken to help me go in the right direction.

I'll post my results upon completion of the repair/adjustment.


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## wrencher2b (Feb 19, 2005)

Work in progress...I've got a question:

Following the expert's instructions, when checking the valve lash/gap, both valves have been set at .010, as recommended. At this gap, the feeler gauge gives a slight resistance when pulling or pushing.

The question is, what is the correct "drag"/ resistance that should be felt on the gapping tool on this equipment? 

Thank you,

Wrencher 2b


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## dawgpile (Apr 28, 2008)

Wrencher.... not sure if you mis-typed or mis-gapped. Just a clarification, the spec is 0.10 mm or 0.004 inch. It's neither 0.010 mm or 0.010 inch.

Also, fyi there are multiple videos on you tube showing how to set the valves on a Stihl 4-mix engine including the FS130.

Good luck!

Kelly


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## paulr44 (Oct 14, 2008)

dawgpile said:


> Wrencher.... not sure if you mis-typed or mis-gapped. Just a clarification, the spec is 0.10 mm or 0.004 inch. It's neither 0.010 mm or 0.010 inch.
> 
> Also, fyi there are multiple videos on you tube showing how to set the valves on a Stihl 4-mix engine including the FS130.
> 
> ...


I looked STIHL's site over (stihlusa.com), but didn't find any info. on 4-mix valve lash setting. BUT, no matter...a 4-stroke valve lash setting is the same method on any common OHV engine today. The only thing that changes is the method of rocker retention and lock-screw/lock-nut etc., the theory is the same.

4-mix...
1. Remove the spark plug (not for safety, is a requirement and should be done with the engine bolted up).
2. Remove the engine cover - 3 screws. Once you've done that, the engine is being held on by only 1 screw, so you can't apply torsional force to it. Sometimes I reinstall the 2 clutch-housing screws, but you can't tighten them fully.
3. Remove the rocker cover on top of the engine.
4. Pull the engine over slowly whilst observing the valves. After watching the intake rocker (closest to the air filter/carb) operate (open and close the valve), and
5 Watch the flywheel and as the magnets pass under the ignition coil, look for an ARROW on the flywheel between cooling fins. When that arrow points at the first coil mounting screw (approx. 12 o'clock), stop. You can move the flywheel by hand to achieve the correct position, which will be TDC on the compression stroke.
6. Set both valves to 0.1 mm, or as you've pointed out, 0.004".
7. Pull engine over a few times and re-check at TDC as described above.
8. Using a NEW rocker cover gasket, re-assemble. Unless you're a total num-nuts and shouldn't own a pocket-knife, the engine should pull over easily and run just fine (all things considered such as fuel/carb. etc. condition).
9. Now, go weed-whacking or Miller Time, your call.


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## paulr44 (Oct 14, 2008)

P.S. VERY IMPORTANT - in almost all instances, the kill-wire harness grommet doesn't move, but always check to see it's seated properly before re-installing the engine cover. It sits about an inch from the coil toward the carb. side...just follow the wires.


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