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Cheap ignition coils


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#1 Cnc ONLINE  

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Posted June 15, 2017 - 01:50 PM

I accidentally shorted out the original magnatron coil on the Briggs opposed twin 16 hp in my 1668 tractor a couple of months back. I shopped around quickly on the net and bought a Oregon replacement coil. After installing it I suspected it was a bit weak, the motor had to spin quite a few revolutions more before firing and starting but once going idled and ran ok. I didn't put more than 5-6 hrs on it since the install but I am thinking the coil is getting weaker. Dispite a strong battery and turning over fast it has been getting harder to start especially hot. A quick shot of carb cleaner ( I prefer that over starting fluid ) in the plug holes would get it going. I thought maybe I was having fuel delivery issues but as soon as it fired up it idled smooth and ran fine. Then that did not work anymore. I still thought I had fuel issues as I still had spark on both plugs when grounding them out of the motor and cranking. No amount of fuel or my carb cleaner could get it to fire. I changed plugs to a new set but resistor style and little to no spark, back to the old non resistor style plugs and a better spark, but still would not fire.
I put the battery on charge for awhile as I had been running it down a bit with all the attempts.
Right after full charge and before the battery settled back down ( reading 13.86 volts ) the motor spun a little faster and started right up, running fine as usual. Same deal this morning cold motor and a full charge battery, it started after several revolutions. Then when warm won't restart despite the motor turning over fast.
My theory now is the coil is weak enough that the carb cleaner having a lower flash point than gas helped it start with less spark and the extra bit of voltage in the battery after a charge helped the motor spin just a bitter faster increasing the voltage a bit from the coil and allowing it to start and once running the increased rpm allows the coil to put out enough voltage to run decent.
Your thoughts?, And any leads on where to get a good used Oem Briggs magnatron or better yet brand new Oem Magnatron would be welcome.
I think most of the new " replacement " coils out there on eBay will be the same Chinese quality labeled under different names.
Thanks.
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#2 boyscout862 ONLINE  

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Posted June 15, 2017 - 03:33 PM

I would clean the flywheel magnets, clean the ground, check the gap, and check the timing. Good Luck, Rick

Edited by boyscout862, June 15, 2017 - 03:34 PM.


#3 Bolens 1000 ONLINE  

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Posted June 15, 2017 - 03:35 PM

I am always of the mindset you pay for what you get, in my years of selling so far the only coils that I have received defective were aftermarket ones, so far no OEM's have ever failed from what myself or customers used.

 

I do stock OEM B&S, if interested send me a PM so I can quote you shipping to Canada

 

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#4 Cnc ONLINE  

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Posted June 15, 2017 - 08:47 PM

Thanks for the replies guys. The magnets and mounting posts were cleaned when I installed the replacement coil and the air gap was set as per the Briggs shop manual. Since it is a big job to get at the coil on this machine, remove the drive shaft, undo the motor mounts and jack the motor up 4 inches to get the space to get tithe cowling off, I might as well replace the coil with a OEM rather than screw around with this one. I am reasonably sure this one does not have the output of a OEM when working right and have since read a few reviews that seem to echo my impressions.
I have PMed Bolens 1000 and hope to get one from him.
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#5 stiemmy ONLINE  

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Posted June 15, 2017 - 11:10 PM

Not to step on any toes here folks, or detour business, but I have never had problems with any of Oregons parts.

 

Before giving up on that unit, try setting the coil gap with an index card in between.  Run the magnets to the coil when you tighten down the coil bolts, after they are tight, spin flywheel to remove card.

 

Lastly, don't completely reassemble the motor, you can check the spark with all that junk off, if it dont work, atlest you won't have to go through teardown again.

 

Try this 1st, nuthin to loose;) Keep us posted.


Edited by stiemmy, June 15, 2017 - 11:15 PM.


#6 Alc OFFLINE  

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Posted June 16, 2017 - 05:25 AM

When you were cranking for long periods of time to you pull the plugs to see if there were wet ( gas fouled  ) ? How's the compression , valve lash ?  



#7 Cnc ONLINE  

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Posted June 16, 2017 - 08:54 AM

Thanks for the suggestions Stiemmy and Alc. Compression is not super turning over by hand but it never was. I though I remembered reading there is a form of compression release on these motors, so never thought much of it. Running normal plugs are a dark chocolate brown, one a little darker than the other, but decent that tells me if it is low on compression it isn't so much from blow by or valve guides but maybe valve seating/ weak springs. It does use some oil though. Plugs were surprisingly dry when cranking and not starting but I did not crank for long periods just repeated tries long enough to know it was not going to start. If it were fuel related in my experience it should have fired with spray down the plug holes. There is spark on both cylinders when grounding out the removed plugs but I am thinking spark under compression may be too weak to fire, especially when the old non resistor style plugs show spark and new resistor style plugs have a hard time showing any spark.
Rainy weekend coming up so I may have time to get into it. I will do a compression test first and double check the air gap next and go from there.
Story and or rant to continue, grin.

#8 LilysDad ONLINE  

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Posted June 16, 2017 - 09:55 AM

A coil is a pretty simple thing. Why would one be weaker? Thinner wire? Fewer windings? Poor plug wire?



#9 secondtry ONLINE  

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Posted June 16, 2017 - 10:19 AM

Week condenser? Don



#10 Cnc ONLINE  

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Posted June 16, 2017 - 02:44 PM

I don't know why one would be weaker, poorly wound? higher resistance? not as many windings? Any of the above and what you guys mention could translate to it not stepping up the voltage as high as the original I guess. If a " fits L head Twin" sells for as little as $12.95 to $32.00 on eBay one has to wonder where the manufacturer cut costs or is one paying a premium for OEM brand names?
In any event I have a OEM coil and a carb kit on the way from Bolens 1000. I don't think the carb is part of the problem, but I wanted one on hand anyway.

#11 Husky OFFLINE  

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Posted June 20, 2017 - 11:02 AM

I've seen an engine that won't start after it gets warm. One that I owned was caused by a cracked coil, the other was caused by low compression and  would not warm start. It ran as long as you did not turn it off.


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#12 Cnc ONLINE  

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Posted June 20, 2017 - 01:42 PM

I'm waiting on another coil before taking everything apart but I did do a compression test the other day. I got a reading of 97 and 100 dry.
Would seem to me that is decent enough to start? Briggs does not publish compression specs for the L head twins as I understand there is a sort of compression release built into the way the cam lobes are ground keeping a valve slightly open during the compression stroke. If that is true, then I am guessing those readings are decent and why the preferred test is a leak down test, but again I have no data to compare my findings if I rigged up something to do one with.

#13 Cnc ONLINE  

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Posted June 23, 2017 - 09:03 PM

Up date on my issue. I received my package from Bolens 1000 today with a Briggs coil and a carb kit. Well it was a rainy day so I dug right into it.
I decided to fiddle with the Oregon coil I installed a few months back first. Checking the air gap again one leg was around 10 thou and the other around 13 thou. I set them a little closer and made sure they were equal at 8 thou and turned the key, it consistently started after about 5-6 revolutions. Ok that's great but I wanted to compare with the Briggs coil. I switched out the coils set the Briggs at 10 thou and turned the key.
Much quicker starts, maybe 2 revolutions max.
So I guess I'll keep the Oregon as a spare but it seems to me it doesn't have as much umph as the Briggs. I just need to reinstall the cowling, fan etc, drop the motor back on it's mounts and reconnect the drive shaft tomorrow.
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#14 Bolens 1000 ONLINE  

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Posted June 23, 2017 - 09:25 PM

Glad to hear it worked out for you!






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