Stihl 4 Mix, I want to de carbonize, Need help with when to pour it in the cylin

JOE.G · August 04, 2024, 09:15:08 PM

Hi, I have Pole saws, Weed whackers and Blowers that have the 4 Mix motor, I have a bottle of the Stihl branded De Carbonizer and it says to pour in when both Valves are open, Is there a way to figure this out with out pulling valve cover? Would piston be at TDC or BDC I am guessing at TDC I could tell if there was no pressure pushing finger off of plug hole that both would be open?

Do you fill it at TDC?

Thanks

PS I have always ran Non Ethanol 90 Plus octane with Stihl Ultra oil. I am not noticing any issues but figured most of these are over 10 Years old with some having a lot of HRS on them and would just do it for Maintenance purposes.

rusticretreater · August 05, 2024, 12:03:53 AM

STIHL Engine Decarbonizing liquid can be used to soften and flush out carbon
deposits. Engine treatment involves putting the piston at top dead center on valve
overlap, where both valves are slightly open at the same time. This is 360° of
crankshaft rotation from top dead center on the compression stroke. With the
valve cover removed this is easy to verify.

JOE.G · August 05, 2024, 10:24:16 PM

Yeah I may just wait if that is the only way until I get ready to adjust the valves. Is Seafoam the same thing or similar as the Stihl stuff is no longer made and is expensive when you do find it.

From what I read these motors tended to have Carbon issues when left to idle to long or poor quality oil was used. The pole saw and weed whacker are getting harder to start when hot but I would not say its bad yet I just notice a difference, Figured I'd De Carbon and check the valves this season.

I sprayed Seafoam into the carbs , two Identical BR 600 Back pack blowers one with low HRS and one with a bit more, the amount of smoke from the higher HRS one was crazy, I did all of my small engine stuff some Chains saws smokes a lot also, Not sure if this really means anything or not. I'll soak the cylinders when i do the valves on the 4 Mix stuff.

realzed · August 09, 2024, 05:37:02 AM

Not sure about the best way to decarbonize stuff - but I do know after using Stihl Ultra oil in my tools (56 string trimmer, 260 and 261 chainsaws, and 800X backpack) that there was always quite a mess at or around the mufflers after a couple of months of usage..
I typically always used an oil ratio a bit richer than 50:1 and I assumed that was the price for, in my mind at least, getting a bit more oil film coating on everything internal, but I got tired after a while of cleaning the spark arrestor screens which always seemed to end up plugged up when I needed the tools the most and when I didn't have a screwdriver or torch at hand to burn off the carbon build up..
So... after a lot of reading I decided to switch to Amsoil Saber premix oil and still use the same 40:1 / 50:1 ratio as always - but don't now see any smoke when starting or running - nor do the screens ever seem to look coated and the exhaust areas are definitely cleaner overall and I haven't needed to clean an arrestor screen in a year and a half now so far..
I'm not an Amsoil fanboy - but it does seem like a lot better product for my usage (everyone's may vary) and although I don't use it at the 100:1 mixture that it apparently is possible to use it at - all of my stuff is a lot cleaner and seems somewhat easier to start up as well!

JOE.G · August 09, 2024, 08:36:09 PM

I use the Ultra at 50:1 and I have been using it since at least 2012, It seems to burn very clean for me, No plug issues no spark arrester issues or anything, I use it in all of my small 2 stroke motors, In my Sleds,Dirtbikes and what not I use either Amsoil or Klotz.