Author Topic: P41 saw spark plug gap  (Read 633 times)

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Offline Bob

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P41 saw spark plug gap
« on: June 20, 2014, 12:29:58 pm »
Anyone know what the spark plug gap should be for this saw? Using Champion plug 885    DJ7Y.  Installed new cylinder, rings, head, flywheel, coil and spark plug it will not start but get smoke out of the muffler like it wants to start, tried putting starting fluid in plug hole and carb but will not start any suggestions.
Thanks

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Offline Warped5

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Re: P41 saw spark plug gap
« Reply #1 on: June 20, 2014, 12:35:27 pm »
IIWM, I'd set it at .025 and run with it.

... but the Acres site shows .030.

Offline fossil

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Re: P41 saw spark plug gap
« Reply #2 on: June 20, 2014, 01:01:43 pm »
I believe the plug you are using is a tapered seat plug. Your saw uses a washer type flat seal. You are jamming a tapered seat into a plug hole not made for it.
Ditch that plug and get a CJ7Y.
See it that helps.
If it doesn't, you may have a timing issue.
Tim

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Re: P41 saw spark plug gap
« Reply #3 on: June 20, 2014, 04:16:22 pm »
don't use starting fluid.
use properly mixed fuel.
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Offline 660magnum

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Re: P41 saw spark plug gap
« Reply #4 on: June 20, 2014, 04:20:28 pm »
In the model airplane world we change over the BPMR7A gasketed spark plugs for the tapered seat version BPMR7F because the tapered seat spark plug is much smaller on the outside. It makes for a more compact engine. There are no modifications required except to just change the spark plug.

I bought a new '87 Cavalier and a couple years later, AC no longer made the gasketed spark plugs and I was forced to use '88 Cavalier tapered seat spark plugs for the rest of the life of the automobile. This never caused any problem in the aluminum head.
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Offline fossil

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Re: P41 saw spark plug gap
« Reply #5 on: June 20, 2014, 09:38:50 pm »
Why use the wrong one when you can get the right one?
Tim

Offline 660magnum

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Re: P41 saw spark plug gap
« Reply #6 on: June 20, 2014, 11:12:19 pm »
The NGK BPMR7F has 5/8'' flats instead of 3/4'' flats like on the NGK BPMR7A. This tapered seat plug is also shorter than the gasketed BPMR7A.

The Champion RDJ6Y is supposed to be the tapered seat replacement for the Champion RCJ6Y but you cannot depend on the external size of them. The external size is not so important with a rubber boot on a chainsaw but when using a metal shielded cap for Radio Frequency Interference situations, size becomes very important.

The shielded cap for the 14mm BPMR7F also fits the smaller 10mm CMR6H plug that's used in the new 500 series Husqvarnas.

My point remains that the tapered seat plug runs the same as the gasketed plug as long as they are the same thread diameter, thread length, heat range, and type. I've swapped them back and forth and checked with a tach under load in several different engines.
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Offline Bob

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Re: P41 saw spark plug gap
« Reply #7 on: June 21, 2014, 11:29:17 am »
Thank you,  for your help I will get the proper spark plug.  Fossil mentioned a timing issue how would you adjust the timing?
Thanks

Offline fossil

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Re: P41 saw spark plug gap
« Reply #8 on: June 21, 2014, 08:55:21 pm »
Bob,

The timing is set by the key in the flywheel which I'm guessing you have in there.
I see you changed your flywheel. If you have the old one make sure the magnets are in the same location and have the same spacing on the old one and the new one.
I don't know if any of the flywheels in that series have different timing but will fit on the crank on your P41.
I would guess that if you are getting smoke out of the muffler you are getting spark but maybe at the wrong time.

You can change the timing by removing the key and rotating the flywheel counterclockwise to advance and clockwise to retard.
I don't see a spec for the timing in the repair manual.

When you had it apart did you check the reed valve to make sure it isn't broken and that it seats well?

The repair manual calls for a plug gap of .030"

let me know if you need a copy of the repair manual for your saw.
Tim

 

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