Stumped on Stihl BR450 Blower Stopping

[lehman live edge slab]

Thanks for the last couple of replies. I have replaced the coil and plug. There was nothing wrong with the original coil. I am convinced the issue is not ignition related. Earlier, I mis-spoke about the fuel/oil ratio. I have only ran 50:1 ratio. I used to have a Lawn Boy mower that was 32:1, and had it on my mind I guess. Last weekend I installed the Stihl carb kit, which consisted of the diaphragm and the piece of film on the other side of the carb that has the two little flappers for the crankcase pulses to pump fuel. The blower ran normally. Yesterday, I ran it and it had the issue again. I found that I could jump up and down, and shake the blower from side to side on my back, and get it to pick up power again. The neighbors probably thought I was crazy. Some times I did have to let it get back down to idle, to let the fuel supply catch up it seemed, and once or twice it stalled out, but I was able to get all the work done that I needed, where before, it would starve out completely and not re-fire for awhile.

Sounds like faulty vent to me, shaking the blower would pressurize the tank to a point. I’m leaning towards tank vent and of filter. I’m sure you changed filter but question is was it oem or aftermarket? Some cheap filters don’t flow properly and or come apart inside.

 

[HusqvarnaDave]

I have a BR450 that I purchased new in 2018, which has performed flawlessly until recently. I am a homeowner who uses it once a week during the summer months, after mowing, and multiple times during the Fall leaf season. I do not believe it is "worn out", like piston rings, crankcase seal, etc. I've always ran 93 octane gas, mixed at 32:1, with the recommended amount of Sea Foam in the mix to keep it clean. I've kept a clean air filter in it. The issue is that, from cold, it will crank up and run as normal, but after 5-10 minutes of wide open throttle blowing, it will quit running. I checked the screen in the muffler, and it is clean. I replaced the fuel filter and gas tank vent. I replaced the coil and the spark plug. None of these things helped. I've removed the plug during these events, and it's dry. My gut feeling is that it's the carburetor, for whatever reason not keeping fuel in the "bowl". I replaced the carburetor, and it ran as normal for a couple of weekend uses. Thinking the problem is solved, but no, the next use it died again after probably 10 minutes. When it does this, it might re-crank once or twice, but will not throttle up wide open, and eventually it won't crank at all. Fuel can be moved using the priming bulb as normal. There is no debris blocking air flow and nothing obstructing the cooling fins on the cylinder, so I don't think it is an overheating issue. The fuel line itself is about the only thing I haven't replaced, but it is supple and looks ok. Any advice is appreciated.

Sounds to me like your fuel tank vent is plugged, the blower runs as it should until it draws enough fuel out to cause a vacuum inside the tank.
To check this, simply crack open the fuel filler cap after it's died, and see if it will restart.
Best of luck..

 

[lehman live edge slab]

Well, getting back to basics here... Next time it wigs pull the plug immediately, put it in the plug wire, ground the threads, switch on, pull the rope and check for spark. No spark, maybe buy a new oem coil or replace sparkplug. Replace every single fuel line and the impulse line with oem rubber lines. Make sure your air filter is in good shape. Pull the muffler and make sure your engine's exhaust port is not loaded with carbon, remove the spark arrestor screen and clean if necessary. 32:1 is a lot of oil for a 4-mix engine. I know a lot of people recommend more oil, but unless you are running a very thin oil 50:1 should be fine. 40:1 max for thin oils. Outboard motor oil "maybe" 32:1. I have been running 4-mix engines for 20 years so I've been there done that. They are not 2 stroke engines and they just cannot gobble oil like many 2 strokes can. Lay off the Seafoam for a while. Any aftermarket parts replace with genuine Stihl oem. I realize I repeated what you have replaced but what I have seen is a bad tank vent so consider oem if not. Air, airtight, airflow, fuel, compression, spark. Most Stihl mechanics will say to never use aftermarket carbs and coils. Oh.... good ngk plug with proper gap. bpmr7a @ .020. Sorry if I left things off, but that's s lot.

The 350/450 are 2-mix engines right around 60cc can’t remember exactly what cc just low 60’s.