Stihl Backpack Blower BR420 Magnum

I couldn't sleep so I went out to the shop. I cleaned the frame underneath the motor and tank and down the exhaust side of the motor. What a mess.

I checked the diaphragm again. That little disc is metal so it should be rigid, however it all is and shouldn't be. All the black rubber should be as soft as silk from what I've researched. That's definitely an issue.

I emptied the tank and checked it out. I appears good and clean and doesn't appear to be leaking.

I reassembled the air filter housing, carb, pull starter etc. Basically everything except the muffler and plastic cover.

I pulled the plug and I checked the compression on the cylinder three times: 75, 80, 80. I would think that's good compression. Before checking the compression I laid it down and pulled it a bunch and no gas or anything came out any holes. If it was overly flooded, it's good now.

When it warms up I'll put some fresh gas in and try to crank it (no choke) without the muffler and see what happens.

Hey Dan......... Yep it's cold here too......... Need to do some outside work myself........ I don't like the highs in the upper 40's and the 50's ...............

So your your metering diaphragm is hard like I thought it would be........ It might run and it might not....... You can use the choke to try and start it... 2 or 3 pulls then back off of the choke.... Did you see the model number on the carb ???

It should be one of the ones that Boo Boo said it was....... I looked it up a while back and think I seen the same number..... I can look the kit number up for you IF you have the carb we talked about .......

Like Bert said earlier about 12 to 15 bux in your area .......... Check to see if your fuel lines are loose where they go into the tank.... Just pull or push them to check.........

Let us know Mon Ami ~!~!

Here's a pic from a customers machine showing the carb INTERNAL FILTER. Pictured is EXACTLY how I found it.




It'll take you longer to remove it than to tear it down. If you access to a Ultra Sonic Cleaner, that is your best bet if it's seriously clogged (I use as a last resort).

Make sure you remove that filter for cleaning as well as the needle. Once I found a piece of crap in between the two which drove me crazy..

I would NOT use carb cleaner on any rubber parts, but brake cleaner. It's not nearly as aggressive. Blowing out the metal body orifices, it's fine...

If you can remove the setting screws (L & H), gently screw them in taking note of the settings. Remove for cleaning and later reinstall to where you removed them.. Stihls aren't bad, but once it starts, slowly start adjusting the "H" (high) screw CC, richening up the mix. Someone may have dinked with it and once running, should help..

But you definitly have a carb issue with flooding and leaning out....