Spark plugs for a 582 special

lbuttke · Aug 9, 2011

I have a 582 special that has a 16hp twin Briggs and scrap-em motor and it is in need of new plugs.

Problem I am haveing is finding a plug that will work.

Old plug is a Champion RJ12C
Purchased 2 Champion RJ12YC and the right cylinder (as seen from the seat) valves hit the plug, causeing it to close shut.
Left cylinder is ok, plenty of cleareance.

What plug(s) can I use ? as I can not locate the Champion RJ12C plug.

kweaver · Aug 9, 2011

Lonny - Be careful as I've (when a kid) had long plugs in and knocked a hole through the piston top.

The reason one side does it and the other doesn't might be because:

A) One side doesn't have the washer seal
B) The other side may have an old washer seal still stuck over the hole giving you 2 on that cylinder. (if the new plug has one)
C) Somebody has just really torqued it in once a few times to many and got the threads going to deep.

Is the "YC" plug the same length from seat to electrode ground as the "C" ?

jchamberlin · Aug 9, 2011

Lonny, I've replaced plugs in that engine without a problem, so, like Ken, I'm suspicious. Are you sure the lower rod isn't worn? Those engines don't have bearings, the rod journal rides right on the crank.

I've still got the engine in the shed, if you need me to check, I'll see what plugs I put in, but I'm sure they were a "match" for the Champion as called for in the Service Manual.

Edit: One more thing, if the plugs have been over-torqued, they might not be "indexed" correctly, so that the electrode could be in a location its not supposed be be, that is, twisted into the path of the cylinder (although I'm not sure if the tolerances are that tight, they might be).

lbuttke · Aug 9, 2011

With the plug removed I can see one of the valves moveing and can now see a nice shinny mark where it hit the plug.
The RJ12YC electrode is longer than the RJ12C, I belive that is the problem and I need to find the short electrode to work.

kweaver · Aug 9, 2011

Lonny - The "YC" is a hotter version of the "C" then.
I use to get that plug a Wally World here and about all automotive stores should have it.
Hope you didn't do any damage.