Stihl BR 600 Blower - Surges at idle, eventually stalls, restarts only at wide open throttle

Riick

Riick

Member
Scratching my head. -New to me- (Age 12) Stihl BR600 Blower. Was never used as a commercial machine.

Cleaned OEM Stihl carburetor passages & Screen & Replaced diaphragm. Set valves to spec. New Fuel Filter, Air Filter, Purge Bulb. Fresh 93 octane gas/synthetic oil mix. New (aftermarket) coil/magneto, new spark plug. Checked kill wires & switch - OK.
When cold, hard to start, pulling starter string, you will lift up the blower if you don't keep your foot on it. Much *much* easier pull when warmed-up. WHY ??

Starts, but will stall unless you run it on half choke for a few minutes.
I increased the idle speed, enriched low speed mixture, and it idled decently, but once I run it at high speed, it surges at idle, and eventually stalls out.
-- H E L P
NOTE: Get very same behavior with the aftermarket carburetor I bought, so switched to original Stihl carb.
 
Riick said:
Scratching my head. -New to me- (Age 12) Stihl BR600 Blower. Was never used as a commercial machine.

Cleaned OEM Stihl carburetor passages & Screen & Replaced diaphragm. Set valves to spec. New Fuel Filter, Air Filter, Purge Bulb. Fresh 93 octane gas/synthetic oil mix. New (aftermarket) coil/magneto, new spark plug. Checked kill wires & switch - OK.
When cold, hard to start, pulling starter string, you will lift up the blower if you don't keep your foot on it. Much *much* easier pull when warmed-up. WHY ??

Starts, but will stall unless you run it on half choke for a few minutes.
I increased the idle speed, enriched low speed mixture, and it idled decently, but once I run it at high speed, it surges at idle, and eventually stalls out.
-- H E L P
NOTE: Get very same behavior with the aftermarket carburetor I bought, so switched to original Stihl carb.
Click to expand...
Did you original ignition coil fail? Is your premix fuel fresh? Have you checked the tank vent and fuel filter?
 
Yes, origina OEMl coil (and spark plug) failed. Thought about vacuum in tank, and tried opening gas cap. Seemed to work, but after running at WOT
-around 6500 RPM- engine stumbled and died again.

Have now
(a) replaced all fuel lines with new & increased ID of fuel supply hose,
(b) reinstalled fuel line hose-barb and grommet on tank used silicone lubricant to insure positive seal,
(c) replaced tank vent.

Fuel is fresh, and has 1 ounce of Stabil/gallon. Dual fuel filters are new.
Will see results this morning.

Note: This engine got Very hot after running at WOT, when removing starter assembly, bolts too hot to touch..
 
The top of the block & fins are clean - IF you're talking about trash, leaf debris, etc. If you're talking about bright metal, no, it's got a brownish-black patina. Fins look like those on every air-cooled lawn mower I've ever seen.

Checked valve clearance, I had set them too loose, now both at 0.10-inch, & starter rope much easier to pull.
That, plus new fuel lines, tank vent, etc., have improved things greatly, but, once it ran at WOT for only a few minutes, RPM became unstable on tach, followed by RPM dropping, and blower stalled out. Wouldn't restart. Consistent with coil overheat and failure. Ignition test gizmo arriving tomorrow, want to be certain it's the coil.
 
Final Report (I think)
I'm embarrassed... Went back to check if it would restart once cooled off. What?? Primer is getting no gas!? Checked fuel level - EMPTY. Is that why it stalled out? Refilled tank, Primed, Choke, 2nd pull she started right up.
Today, I ran the Blower for about 30 minutes, 20 minutes at WOT. Ran steady at about 7,200; release throttle and immediately idled nicely at 2,600 when throttle released. Restarted easily while still hot. Apparently the replacement aftermarket coil is OK.
So for anyone else who reads this, solution was properly adjusted valves, unrestricted fuel lines, properly sealed hose barb (& its grommet) on fuel tank, good coil & spark plug, and (always check the basics) enough fuel!
 
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replacing the diaphragm is what probably fixed it. Those carbs don't last all that long if fuel is left in them when shut off. I finally got years of service without problems by completely draining the tank after every use, and running the engine until it died. That was true for multiple devices here that have that style carb. When they do start acting poorly, replacing the diaphragm fixes them each time.
 
sgkent said:
replacing the diaphragm is what probably fixed it. Those carbs don't last all that long if fuel is left in them when shut off. I finally got years of service without problems by completely draining the tank after every use, and running the engine until it died. That was true for multiple devices here that have that style carb. When they do start acting poorly, replacing the diaphragm fixes them each time.
Click to expand...
Draining the fuel and running handheld equipment until it dies is both unpractical and unnecessary. When not using it for extended periods of time, yes, but after each time you use it, no.
 
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