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Greetings,
Anyone have the service manual for above blower. Machine not starting and need to go for a dive. Apparently there is something that needs replacing regularly. Be nice to have the shop manual to go off. Cheers mat

Stihl does restricts all service and IPL manuals to dealers only in the US.

And I can't even find a BR 850 listed on the Stihl website. I will do digging in my library source but that will take a while as that manual may not even exist yet there for me to even get and read myself.

On stihl 4mix blowers the first things i check are spark, spark arrestor and valve lash. Every one that comes in using HP ultra oil has the spark arrestor plugged.

Hammermechanicman said:

On stihl 4mix blowers the first things i check are spark, spark arrestor and valve lash. Every one that comes in using HP ultra oil has the spark arrestor plugged.

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Yes spark arrester plugging is a common problem with Stihl equipment. Even those darn orchard wasps are a pain when they plug up the arresters.

Plus a lot of the customers don't even know these 4 mix have valves that has to be adjusted due the way Stihl use a 2 cycle fuel mix setup.

My dealer is asking are you sure it is a BR850 and not a BR350?

If BR850 post an image of the label so I can forward it to my dealer to verify what we are looking for.

I was told its an 850. I can’t see them anywhere so it must be an 800. Not ID on the machine due to heavy use. It’s a magnum if that helps.

I managed to track down the clearances (0.10mm) and they were miles out. Adjusted and still wouldn’t start. Looks like the carb is stuffed. Local dealer wanted $280 for a new one. Going to give the cheap fleabay carbs a go. Considering the genuine Stihl carb has China stamped on it, what could go wrong.

Also chasing the manual for a BR450 but if anyones got one. Need to replace the crank bearings and seals. I believe the MS270 bearings will fit.

What the number on the carb? That might narrow down the model #. As for could go wrong just about anything when guessing.

As for the seals and bearings yes the BR450 and MS270 uses the same one per the IPLs here.

9639 003 1585 Seals
9523 003 4300 Bearings

Carb number is 4283/010021L

100388G appears beneath and I’m guessing is a serial number.

A quick google search brings up a heap of listings for 4283 120 0601. The look identical and I’m guessing should work. If a couple of things are out, might just be able to swap over from the genuine.

You have a BR800. The carburetor PN is in the current format.Stihl several years ago change how they labeled the Zama carburetors after they brought a controlling interest in Zama.


To narrow it down further look for the 11 digit model number on the serial number tag.

Carburetor info

The 4283 007 1700 carburetor info is the Stihl GND kit.

That model number is 4283/01C which means it is revision C. The rest of the number are factory and date codes.

A picture of the whole unit would be helpful. I have worked on a BR550 and to take the covers off is a real puzzle as they are overlapping bolt holes and some inter connections. It can be done, but the learning curve is steep for the disassembly and reassembly. I had to replace the priming bulb and that cause me to get into the whole unit. I see some of the same on other Sthil units.