Stihl BG 85 woes!

[gmax]

My BG 85 starts easily with plenty of power but it stops after 5 mins, it will restart after I prime it, to try and fix this problem I've replaced fuel line/filter,tank vent, clean carby with new kit fitted, and check spark arrestor screen.
I'm beginning to think maybe the coil is the problem, anyone had similar problems with these blowers?

 

[josh1981]

well mine would start up fine but full gas would bog down. I simply ajusted the LA screw. Now runs like brand new.

Maybe that will help?

 

[gmax]

I tried adjusting the low screw, it didn't help.

 

[talon1189]

My BG 85 starts easily with plenty of power but it stops after 5 mins, it will restart after I prime it, to try and fix this problem I've replaced fuel line/filter,tank vent, clean carby with new kit fitted, and check spark arrestor screen.
I'm beginning to think maybe the coil is the problem, anyone had similar problems with these blowers?

I do not own a BG85......It sounds like the carb is running out of fuel. How many hours are on the blower?

 

[gmax]

I'm not sure how many hours are on it, when I had the carby off the piston/cylinder looks good, it has plenty of power when running.

 

[josh1981]

dirty fuel line/filter? plug good? dirty air filter?

 

[gmax]

dirty fuel line/filter? plug good? dirty air filter?

No there all good, that's the first thing I checked.

 

[josh1981]

bad carb?

 

[gmax]

I suppose I could find another carby for it, one with H & L adjustments.

 

[josh1981]

mine came with h l la ajustments stock. i have never had a problem with mine just had to ajust la screw a few days ago. i dont understand why your having problems.

 

[gmax]

mine came with h l la ajustments stock. i have never had a problem with mine just had to ajust la screw a few days ago. i dont understand why your having problems.

I just had another play with it, after it stopped I removed the plug ,the top of the piston is bone dry, I think I'll try another carby.
These have a fixed jet in the carby the H adjustment wouldn't do much.

 

[PasoRoblesJimmy]

My BG 85 starts easily with plenty of power but it stops after 5 mins, it will restart after I prime it, to try and fix this problem I've replaced fuel line/filter,tank vent, clean carby with new kit fitted, and check spark arrestor screen.
I'm beginning to think maybe the coil is the problem, anyone had similar problems with these blowers?

Bad batch of gas? Happened to me once with a Stihl FS-76 trimmer. Got fresh gas from a different gas station and it ran fine.

 

[gmax]

Nothing to do with gas, I use the same batch gas for my chainsaws & they run fine.

 

[PasoRoblesJimmy]

Nothing to do with gas, I use the same batch gas for my chainsaws & they run fine.

The batch of gas that my trimmer wouldn't run on worked fine with my 2 chainsaws.

 

[gmax]

This batch of gas has been used with 15 different chainsaws, besides why would it easily start & run for 5 mins then stop?

 

[Streblerm]

Replace the carb!

I had an SH85 which is the shredder/vac version of the BG. It ran flawlessly until the fuel lines deteriorated. After replacing the fuel lines I could never get the thing to run right. It would run for a few minutes and then just die. I bet i had that carburetor apart 20 times if it was once. I soaked, boiled, baked, ultrasonically cleaned...you name it. I could never get it right. I replaced the carb with an adjustable unit and all was well.

There must be a check valve or something in that carb that can't be cleaned, I don't know. All I know is that I suffered much frustration trying to get that thing running, many bad words were spoken, and the aerodynamics of the blower were tested several times.

 

[gmax]

I had an SH85 which is the shredder/vac version of the BG. It ran flawlessly until the fuel lines deteriorated. After replacing the fuel lines I could never get the thing to run right. It would run for a few minutes and then just die. I bet i had that carburetor apart 20 times if it was once. I soaked, boiled, baked, ultrasonically cleaned...you name it. I could never get it right. I replaced the carb with an adjustable unit and all was well.

There must be a check valve or something in that carb that can't be cleaned, I don't know. All I know is that I suffered much frustration trying to get that thing running, many bad words were spoken, and the aerodynamics of the blower were tested several times.

The carby looks to be the problem, what brand/model carby did you replace it with? I'm sure another carby would fix it.

 

[angelo c]

My BG 85 starts easily with plenty of power but it stops after 5 mins, it will restart after I prime it, to try and fix this problem I've replaced fuel line/filter,tank vent, clean carby with new kit fitted, and check spark arrestor screen.
I'm beginning to think maybe the coil is the problem, anyone had similar problems with these blowers?

Gmax,
when you rebuilt the carby did you replace all the needles and jseats or just the diaphrams. More often then not the needle valves wear and they just won't seat proper. I will never cut that corner again. if you order the rebuild kits make sure all the needles and seats come with it. Cuts down on the "flight testing" of the units....and much less cursing.

if that's not it I would go with an ignition. I wonder if anyone will send you a spare one just for process of elimination purposes.
A
A

 

[WildnCrazyGuy]

Gmax,

if that's not it I would go with an ignition. I wonder if anyone will send you a spare one just for process of elimination purposes.
A
A

I'd love to have that option on a BR600 Blower I have. I think it's something in the carb, but I've been through it, even put a kit in last night, gaskets and diaphrams only, But would love to have a known good carb to slap on it just to see... Anyone know if the carbs on an SH85 are the same as a BR600? I know a little different setup with the primer bulb, but I've got an SH85 I can tear apart to test with, maybe. I just don't have IPL's for the two and hate to tear down my SH85, only to find it won't work...

 

[gmax]

I just replaced the diaphrams, I'll replace the needle and see if that helps