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Backfiring: duck and cover!


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#1 aevansgatech OFFLINE  

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Posted June 30, 2015 - 12:35 PM

Can anyone tell what's going on in this (poor) video?

12 hp Briggs, I have spark, but consistent backfires and no start condition

http://youtu.be/wRNL8U-ABik

#2 glgrumpy ONLINE  

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Posted June 30, 2015 - 12:39 PM

Flywheel key? Points adjust?
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#3 Bolens 1000 OFFLINE  

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Posted June 30, 2015 - 12:51 PM

Sounds like ignition or improper valves clearances/seating

 

What model engine?



#4 aevansgatech OFFLINE  

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Posted June 30, 2015 - 12:54 PM

281707

12hp L-head one cylinder

Grumpy, the flywheel key looked good when I had it out, but I can check that again

Bolens, as I'm working through the L-head engine manual something struck me. I lined up the camshaft timing mark with the crankshaft key. Should there be a different timing mark on the crankshaft gear? Maybe my timing really is off

#5 Bolens 1000 OFFLINE  

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Posted June 30, 2015 - 01:10 PM

The way your engine is acting it definitely points towards timing as an issue

 

Have you had this engine apart? If so you could have been a tooth or two off the mark



#6 boyscout862 ONLINE  

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Posted June 30, 2015 - 01:56 PM

Sometimes a sticking valve can be the problem.



#7 olcowhand ONLINE  

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Posted June 30, 2015 - 02:17 PM

Most every engine I've ever worked on had a dot on both the crank gear and camshaft gear.  Sometimes it will be an angle cut on the matching teeth.  It's either cam timing off or a sheared flywheel key.


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#8 crittersf1 OFFLINE  

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Posted June 30, 2015 - 03:04 PM

Most every engine I've ever worked on had a dot on both the crank gear and camshaft gear.  Sometimes it will be an angle cut on the matching teeth.  It's either cam timing off or a sheared flywheel key.

I agree.


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#9 aevansgatech OFFLINE  

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Posted June 30, 2015 - 09:16 PM

Alright I found the problem!

Pulled the engine again, checked the timing gear and camshaft and sure enough there is a tiny timing mark on the timing gear. I had it aligned with the key and not the timing mark so I was at least 30 degrees off

It's looking promising that tomorrow she might finally come back to life!
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#10 aevansgatech OFFLINE  

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Posted July 01, 2015 - 07:07 PM

Alright fellas, progress!

She fired up for the first time in many years. Not the smoothest start, but I did have it running for longer.

http://youtu.be/XVT5WNALzP8


I had to disconnect the spark stop wire to get it to start, so I'm sure that wire is chewed up

I also don't have the drive belt connected, so the engine was just spinning freely. Seems like I need to make a couple carb adjustments too
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#11 MH81 ONLINE  

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Posted July 01, 2015 - 08:53 PM

Sounds pretty good,
Like you said, a few things to work out, but it RUNS. :dancingbanana:

#12 alec OFFLINE  

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Posted July 01, 2015 - 09:39 PM

glad to hear it ! congratulations  :thumbs: 



#13 aevansgatech OFFLINE  

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Posted July 10, 2015 - 07:00 PM

Ok so it's running better.. But not great...

I still have a problem with my ignition armature ground wire. I have to unplug it to get spark and to start the tractor. I debated changing it but I tested it with a multimeter and found no resistance across it so it should be ok.

Stuck.. ?

#14 MH81 ONLINE  

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Posted July 11, 2015 - 06:23 AM

What wire are we talking about? The one that ends up at the key switch?
When you say won't start, won't roll over or no spark?

#15 aevansgatech OFFLINE  

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Posted July 11, 2015 - 08:34 AM

The wire going from the ignition armature to ground (near the governor)

When I have it unplugged, the engine will start

When I have it connected, the engine will turn but has no spark




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