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Old 10-29-2012, 09:07 AM
keith.mcginnis's Avatar
keith.mcginnis keith.mcginnis is offline
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Location: Knoxville, TN
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Help me get this BR400 running

Well I had someone give me this Stihl BR400 blower that quit working on them. I'm not sure what that means.. If it died, or just wouldn't start one day.

Anyhow, it a decent looking blower. I just can't get the bastard to run. Here is what I know and what I've done.

Conditions:
Compression around 120psi
Unit gets spark while using my spark tester My Spark tester
Tries to run after a little starting fluid (with upper cylinder lubricant)

What I've done:
Checked Flywheel and key - Magnets were strong, key not sheared
Regapped coil
New NGK Plug
Soaked Carb in Seafoam and replaced diaphragms and pump
Checked Carb mounting flange/spacer for cracks and replaced gaskets
New Fuel Line
Checked Fuel Filter
Removed spark arrestor screen
Removed muffler and torched the inside


What really puzzles me as I try to troubleshoot this blower is, Spark always test good (according to my method) and the plug always seems wet and smells like fuel after cranking. My first inclination when I got this blower was the coil, and I still don't trust it. But if the coil was bad would the engine run for a few seconds on starting fluid? What am I missing here?

Should I replace the Carb? Coil? What does everybody think? I really appreciate everyones help. I can link you to a Parts Guide and Service Manual if needed.

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Old 10-29-2012, 09:13 AM
RussellB RussellB is online now
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Are you sure the on/off switch works?
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  #3  
Old 10-29-2012, 09:29 AM
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keith.mcginnis keith.mcginnis is offline
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Russell,

Thanks for the help. The only reason I know that it works is because it sparks on the tester to ground and at the plug when grounded. When in the up position.

Does a wet plug necessarily mean the carb is functioning properly?
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Old 10-29-2012, 10:18 AM
dhardin53 dhardin53 is offline
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Check closely the spark arrester in or at the end of the exhaust hole. This screen will get just slightly clogged and cause a hard to start issue (or run for a short time and stop).
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Old 10-29-2012, 10:43 AM
dhardin53 dhardin53 is offline
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Sorry is did not see you already address the spark arrestor issue.


Notorious for hard to start, when cold ALWAYS start with a full fuel tank, a full tank aids in the amount of pulls it take to get gas up to the carb. Some guys i know will turn blower on it side till it starts to fire.

Also get a large rubber band to hold the trigger throttle wide open, Some say this helps. This is some of the issues with a wet plug, when starting at a near ideal the fuel to air mixture is going to get the plug wet if at ideal. It don't take long for even a new plug to foul out if you continue to trying to start. Once you have a very wet plug. STOP let it dry out some and then continue. This is why the rubber band trick CAN help in some cases.

Starting fluid has a higher flash point making it easier to start but not run with a fuel mix. Your mix may have to much oil in it. for now try a lighter mix of oil to gas mix.

Last edited by dhardin53; 10-29-2012 at 10:51 AM.
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Old 10-29-2012, 10:54 AM
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keith.mcginnis keith.mcginnis is offline
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Now that you say that. It doesn't have very much fuel in it. Ill put some more in it and try that.

I also tried the throttle wide open trick, to get some more air in the cylinder.

I didn't mention before, that did get it running 1 time. Randomly, for about 2 mins. It never would clear up. Once I shut it off, It would not fire again.
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  #7  
Old 10-29-2012, 11:11 AM
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keith.mcginnis keith.mcginnis is offline
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Quote:
Originally Posted by dhardin53 View Post
...Starting fluid has a higher flash point making it easier to start but not run with a fuel mix. Your mix may have to much oil in it. for now try a lighter mix of oil to gas mix.
Is it possible a weak coil may fire with the starting fluid, but still be a bad coil?
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Old 10-29-2012, 11:30 AM
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BigFish BigFish is offline
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Quote:
Originally Posted by keith.mcginnis View Post
Is it possible a weak coil may fire with the starting fluid, but still be a bad coil?
Yes. Most Stihl coils have a built in rev limiter, that when heading south, can cause an intermittent spark etc.
You also want to make sure the fuel line is in good shape and the primer and lines are good.
But I think you'll find the coil has taken a dump.
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Old 10-29-2012, 11:35 AM
dhardin53 dhardin53 is offline
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Possible. Judging week coil is difficult. Most usually if its a weak coil it will start but not restart. The coil gets hot or warms up and then fails. If you have a multi tester meter you might test the Resistance of the coil. This can also be misleading, the amount of spark can look good but not be enough to spark after 10 to 30 good sparks then fade away..

If you have done all other checks a new coil could be your answer. But in the mean time there is a few more things to check.

http://assets.fluke.com/appnotes/ele...r/B0271b_u.pdf

You said you have good compression, but you may have out of adjustment valves causing the combustion timing to be short.(you have good compression) poor compression is valves staying open to long, or burnt/bad.
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  #10  
Old 10-29-2012, 11:37 AM
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keith.mcginnis keith.mcginnis is offline
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I did replace the fuel line, but this model does not have a primer bulb. I wish I had a good know coil to test with. Kind of hard justifying a new coil if i'm not 100% sure that's the problem.
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