4-mix questions

[jts560]

I just picked up a used FS-130R with the 4-mix. I replaced the air and fuel filters, spark plug, cleaned the spark arrestor and adjusted the valves. I've heard that they have a few quirks.

Stihl suggests to decarbonize the engine every 150hrs. I assume this has never been done to my unit so I ordered the cleaning fluid from Stihl. My understanding is that you pour it in, let it sit and pour it out. It seems that the fluid wouldn't contact the valves much with this method. Is this correct? Should I shake it around or turn it upside down, on it side, etc.?

I adjusted both valves to .004. On a couple of lawncare/small engine fourms it was mentioned that the 4-mix runs better if the exhaust valve lash is set to .008. Is there any truth to this or just BS.

Is the carb adjusted the same as a regular 2-cycle? How do I know when the high and low are set right?

Is there anything else I should do to "baseline" this unit? I will recheck the valves after I decarbonize it.

It seems to run pretty well, but never having used another 4-mix I don't have a true reference to compare it to. So far I like it, especially the torque. It sounds cool too, but it's loud!

 

[D'Animal]

Remove the top schroud.
Remove valve train cover.
Turn the engine so the piston is TDC with both valves open. (Both rocker arms will be tight) You add the decarbonizer and let it sit of 15 minutes.
Drain the fluid.

To adjust the valves:
Remove the top schroud.
Remove valve train cover.
Find the arrow on the flywheel.
Line up the arrow with the right side of the ignition module while keeping an eye on the rocker arms. (Right side of the module will be if you are looking from the throttle grip.)
Turn the engine so the piston is TDC with both valves closed. (Both rocker arms will be loose).

Adjust the valves
Inlet valve: 0.10
Exhaust valve: .015 - 0.20

Put it all back together using a good or new valve cover gasket.

Run the unit and watch the carbon blow out of it.

Generally the valve adjustment is only done after the first 180 - 200 hours of operation. It is not a routine maintenance item. You will have to decarbon the unit more if you use crappy oil or the unit idles a lot.

 

[jts560]

Thanks D'animal. I should clarify, I set the valve clearance to .004in.

When I set the High speed screw on a traditional 2-cycle, I lean it out until it smooths out and the rpm's peak, then I turn it back just until it is rich enough to stumble a little at WOT. I don't have a tach. Is it similar for a 4-mix?

 

[D'Animal]

It is very similar to a 4 cycle. There is a built in rev-limiter that you can hear at WOT so getting it to run "smooth" with no load may be difficult.

Here are the static settings:

With the limiter caps removed on the FS/KM 130 running the Zama (C1Q-S98)
Open the high speed screw H 4 turns counterclockwise.
Open the low speed screw L 2 3/8 turns counterclockwise.
Make sure you install new limiter caps so the screws do not vibrate in or out. The part # for the limiter cap is 4229 121 2701

With the limiter caps removed on the FS/KM 130 running the Zama (C1Q-S130)
Open the high speed screw H 4 1/2 turns counterclockwise.
Open the low speed screw L 2 1/2 turns counterclockwise.
Make sure you install new limiter caps so the screws do not vibrate in or out. The part # for the limiter cap is 4229 121 2701

 

[jts560]

Thanks again. I'll reset the valves after I do the decarbonization and adjust the carb to those settings. I can't wait to see if it yields even more power.

 

[fj40charles]

Get some Stihl Ultra full synthetic 2 cycle mix. Should do a nice of job of keeping the piston/valves clean.

 

[jts560]

I'm going to switch to the Stihl synthetic after I use up my last two bottles of Shindaiwa oil.