Stihl 4-Mix


Old 10-25-09, 12:38 PM
Thread Starter
Join Date: May 2009
Location: St. Albans, Herts, UK
Posts: 95
Stihl 4-Mix


I recently bought a Stihl BR-550 (4 mix backpack blower 65cc). Runs brilliantly, loads of power (previously had a ryobi hand held thing). But some googling revealed mixed opinions about 4 mix. So, my questions to you are

1. What are your opinions on it?
2. What maintenance should I do? (Decoking, valve adj periods (etc), vary from source to source)
3. Should I use regular or synth oil (again varys)

Many thanks, Benjamin
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Old 10-25-09, 01:48 PM
Join Date: Feb 2008
Location: usa
Posts: 755
I have worked on several 4-MIX products in the last few years. The problem I have seen most is ignition module failures. These failures are difficult to diagnose since the module continues to fire just not at the correct time. Keep your proof of purchase because the module has a lifetime warranty, MAYBE. The Stihl warranty states the ignition module is warranted as part of the emission warranty. Some dealers replace the module as part of the warranty. A dealer I know does not consider an ignition module failure resulting in a no start condition to affect the emissions of the engine. You will need to ask your dealer about the maybe

Carbon is inevitable in 2-cycle engines. The more oil you add to the fuel/oil mix the more carbon. Do you need to use it annually, that depends on what you use for your fuel/oil mix.

The owners manual says adjust valves after 139 hours then as required. You should refer to the owner’s manual for items to check and maintain.

I would use only Stihl oils and 89-octane gasoline per the user’s manual.
Old 10-28-09, 01:02 AM
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Join Date: May 2009
Location: St. Albans, Herts, UK
Posts: 95

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