"4-mix"?

[Stihldoc]

A year and a half ago at Stihl Gold School I spent a day in the emissions lab testing (and burning up) 2 cycle engines. The engineer I worked with told me the 4Mix engine was designed in the 1930's by BMW. If my memory is correct and the story is true, a Stihl engineer apprenticed with BMW and saw this technology in their archives. Several years later he took a job at Stihl and suggested this engine for power equipment. Stihl supposedly bought the design from BMW and modernized it for their uses. BMW decided that they didn't need this design back then, couldn't get to run right, or it was more expensive to produce than their existing motors. Whatever the origin, the Stihl and Shindaiwa motors differ substantially in the scavenging of the crankcase and despite many similarities, are completely different motors. I own a KM110 powerhead with the string trimmer, straight shaft edger, and the pole pruner attachments. I am completely satisfied with it. It runs well and has TONS of torque. The only problem Stihl has had with the 4180 powerhead is some of the earlier ignition modules. These modules would get "stuck" in the most-advanced timing stage and not retard for startup. The units "ran great until shut off" then wouldn't restart. Spark would be present, just at the wrong time for startup. This problem has been solved since mid 2005 but we see several units a month for warranty replacement of the ignition module. Despite this one problem, I highly recommend this unit.

 

[THALL10326]

A year and a half ago at Stihl Gold School I spent a day in the emissions lab testing (and burning up) 2 cycle engines. The engineer I worked with told me the 4Mix engine was designed in the 1930's by BMW. If my memory is correct and the story is true, a Stihl engineer apprenticed with BMW and saw this technology in their archives. Several years later he took a job at Stihl and suggested this engine for power equipment. Stihl supposedly bought the design from BMW and modernized it for their uses. BMW decided that they didn't need this design back then, couldn't get to run right, or it was more expensive to produce than their existing motors. Whatever the origin, the Stihl and Shindaiwa motors differ substantially in the scavenging of the crankcase and despite many similarities, are completely different motors. I own a KM110 powerhead with the string trimmer, straight shaft edger, and the pole pruner attachments. I am completely satisfied with it. It runs well and has TONS of torque. The only problem Stihl has had with the 4180 powerhead is some of the earlier ignition modules. These modules would get "stuck" in the most-advanced timing stage and not retard for startup. The units "ran great until shut off" then wouldn't restart. Spark would be present, just at the wrong time for startup. This problem has been solved since mid 2005 but we see several units a month for warranty replacement of the ignition module. Despite this one problem, I highly recommend this unit.

You are correct but he didn't tell ya everything. He didn't mention them fellers in WW2 who wanted such a design for some very unfreindly airplanes but we won't go there. Its a great engine. Modules were a problem for awhile. Ole Stihl already put it on a chainsaw over in Germany and they say it cuts like crazy but the loggers hated it, reason being it didn't seem like a chainsaw to them so for now its on hold. I think a big 4-mix on a saw would be a bad mutter.............

 

[Lakeside53]

I've seen the ignition modules stuck in full retard also. Starts great but won't rev up to full power. Sounds like a rich carb, but isn't.. easy to get mislead...

The were carb problems on the 4180. The fuel pump is a large diaphragm on the bottom of the carb (large because the crankcase pressures are so low on 4 stroke); the screws that hold this in place were getting loose and allowing leaks. Also, Stihl published a tech note note saying ONLY to use the new (then) low smoke oil in the black bottles. It's a 'semi-synthetic" and apparently has less tendency to stick the fuel pump diaphragm to the carb.

 

[THALL10326]

I'm bringing this topic up again hoping that the people who have been operating the 4 Mix units for a while can give me their opinions.

I am thinking about buying a couple of trimmers-on-a-stick, namely the Stihl HL 100.

So, what is the word on the Stihl HL 100 ??? (And the 4 Mix in general.)

Thanks

Instead of buying the HL get the KM and use it for all sorts of jobs. Just snap in a different attachment and your set to go.