Stihl 4-MIX

[Termite]

I am working on a friends Stihl FS110 4mix. It will not start. It has compression. The valves open and close. Spark around 8K volts, same as my chainsaw. Spark plug looks clean and fires. Even with a little starting fluid it doesn't even pop. Any ideas?

 

[THALL10326]

I am working on a friends Stihl FS110 4mix. It will not start. It has compression. The valves open and close. Spark around 8K volts, same as my chainsaw. Spark plug looks clean and fires. Even with a little starting fluid it doesn't even pop. Any ideas?

Do a leak down test. If it passes replace the ignition module. They were known for getting stuck in the advanced mode and when they get stuck starting is impossible. They will fire but thats all..

 

[lcso10]

I agree with the KING on the coil. One thing I would add is, get rid of the starting fluid.

 

[THALL10326]

I agree with the KING on the coil. One thing I would add is, get rid of the starting fluid.

Yup yup. If the coil is stuck in the advance timing mode starting fuild is not gonna do anything. Another thing, that coil is warrantied for 5 years if the unit was bought after 3/03. If it was bought before its warrrantied for life. Check that seriall number on that unit, maybe its covered. If not about $48.00....

 

[Kenskip1]

No Go,

Try this stunt.Normal starting procedure except,"Leave the throttle at idle" With the throttle open you are loosing all negative pressure that draws gas inside the cylinder.Ken

 

[Termite]

Thank You all for the information.
Brian.

 

[fishercat]

i notice..............

they seem to gum up if you don't run the Ultra oil.

 

[warjohn]

My KM110 acted the same as you describe. My nephew even tried starting fluid with no luck. He will never use starting fluid on my stiff again. It had a burnt valve. Replaced the valve and it runs great now

 

[lcso10]

they seem to gum up if you don't run the Ultra oil.

I am not sure about the gum up part. Mine never sits long enough.

 

[Paul001]

Have you adjusted the valves? With the 4 mix you should only be running Ultra (synthetic oil). Otherwise you will have enough carbon deposits that it will keep them from fully closing.

Do a leak down or take it in to have it done.

Otherwise, as Tom has said, coil. We don't see many of these go down but when they do, so far, it has either been valves (will show up in the leak down) or coil.

Other than that, pretty bullet proof.

 

[Streblerm]

Could anyone enlighten us on the valve adjustment procedure? I have been thinking about adjusting mine as preventative maintenance

 

[kevlar]

Could anyone enlighten us on the valve adjustment procedure? I have been thinking about adjusting mine as preventative maintenance

Stihl has a custom feeler gauge that you use.pull the head,set it a tdc insert feeler gauge tighten adjusting nuts until feeler gauge slids in snugly reinstall head.

 

[Kogafortwo]

Stihl has a custom feeler gauge that you use.pull the head,set it a tdc insert feeler gauge tighten adjusting nuts until feeler gauge slids in snugly reinstall head.

I took a regular feeler gage 0.004" (0.10 mm) and trimmed the tip down to where it would fit under the rocker arm.
TDC is when the magneto is aligned with the coil electrodes and both rocker arms should be feel a little bit loose.

The rest is just like Kevlar said. The whole procedure takes 10 minutes if you are working slow.

 

[Streblerm]

I took a regular feeler gage 0.004" (0.10 mm) and trimmed the tip down to where it would fit under the rocker arm.
TDC is when the magneto is aligned with the coil electrodes and both rocker arms should be feel a little bit loose.

The rest is just like Kevlar said. The whole procedure takes 10 minutes if you are working slow.

Thanks guys, very helpful. What is the recommended service interval, or is it whenever they start running crappy?

 

[andybcumming112]

http://golftechs.us/Reference/4.pdf

 

[CentaurG2]

I am working on a friends Stihl FS110 4mix. It will not start. It has compression. The valves open and close. Spark around 8K volts, same as my chainsaw. Spark plug looks clean and fires. Even with a little starting fluid it doesn't even pop. Any ideas?

My ht131 had the same problems. Would not start for love nor money. Turned out to be the ignition module. Fixed under warrantee.

 

[Stihl088stock]

4-mix troubles...

I've been working on a friends FS90 for the last few weeks and it is becoming my bane...

Two years old, he claims to have only used stihl HP Super, although I told him a number of times to go with synthetic.

That aside, it was acting like the carb was out of adjustment or it had an air leak. Compression was down to about 90. I bought some decarbonizer and valve gasket and guage kit. Did the decarbonization process twice and then adjusted the valves. Had the compression up to 120 and it was running fine. I then put a new spark plug in it and it wouldn't run well at all. checked the compression and it was at 40!!!!

I just bought a harbor freight leak down tester (spark plug adapters dont fit!!!!) So my next step was to tear down the engine.

The inside of the crankcase was littered with chunks of carbon, the valves were still coated although the exhaust valve had what looked like clay on it (burnt carbon) I pulled the exhaust valve out and the seat was dashed with spots of black carbon, obviously the problem. I should have taken a picture before I cleaned the valve, what a mess!

Anyone have any comments? Whats the best way to clean the carbon out of the cylinder? More decarbonizer? Thanks for any help, this is my first 4-mix teardown!

 

[Stihl088stock]

photo after some cleaning, I wiggled too much to focus inside

 

[Stihl088stock]

Looks like the EDTA made the chunks of carbon migrate into the crankcase. It did a great job of removing the rest of the junk on the engine head with aid of a toothbrush. There is some piting on the crankcase, I'm not sure what caused it.

I'm guessing this was run on too much oil. After cleaning the valves look new. Oddly, the top of the intake vavle guide shows a jagged surface, but everything else looks ok.

I'll just keep having this conversation with myself...

 

[2000ssm6]

Yup, the reason why customers are told to run Ultra mix.