John Deere 425

[bertsmobile1]

First check they are the right plugs.
On a mower engine the piston should never get any where near the plug so I an guessing some one put in the wrong plugs.
Those are "Projecting Electrode" type plugs.
SO my very first thing would be to swap them for BR4ES, the P is for the longer center electrode.
The piston hitting it will do damage to the piston , rod & even the crank.
Do not use the engine in that condition.

 

[bertsmobile1]

Stick some thing down the plug hole and put a bit of weight on the piston, then rotate the engine. If you feel a "click" any where, the rod is loose or bent.

 

[DevonD]

I stuck a 3/8 drive extension in the hole and turned the flywheel while pushing on the piston and never heard or felt anything. I have know idea what model I have beings there is no serial # on front of engine. So many revisions...



Kawasaki Spark Plugs Table Two

All plugs specified are NGK brand.

Engine Model Rev. A Rev. B Rev. C Rev. D Rev. E Rev. F Rev. G Rev. H Rev. J Rev. K
FD590V S05 BMR6A BMR6A
FD590V S06 BMR6A BMR6A BPR4ES
FD590V S07 BMR6A
FD590V S09 BMR6A BMR6A BPR4ES BPR4ES
FD611V S00 BMR6A BMR6A BPR5ES BPR5ES
FD620D S03 BMR4A BMR4A BMR4A BMR4A BPR4ES
FD620D S08 BMR4A BMR4A BMR4A
FD620D S12 BMR4A BMR4A BMR4A BMR4A BMR4A BMR4A BPR4ES BPR4ES BPR4ES
FD620D S13 BMR4A BMR4A BMR4A BPR4ES BPR4ES BPR4ES
FD620D S14 BMR4A BMR4A
FD620D S15 BMR4A BMR4A
FD620D S16 BMR4A BMR4A BMR4A
FD620D S17 BMR4A BMR4A BMR4A BPR4ES BPR4ES
FD620D S18 BMR4A BMR4A BPR4ES BPR4ES
FD620D S19 BMR4A BMR4A BPR4ES BPR4ES
FD620D S20 BMR4A BMR4A BMR4A BPR4ES
FD620D S21 BMR4A BMR4A BPR4ES
FD620D S23 BMR4A BPR4ES

 

[DevonD]

I will give the BMR4A a try. Hopefully they are shorter. It looks like that is really the only other one listed for this motor. I just remembered too when taking cylinder 2 plug out that the threads were slightly striped...that must be because the piston kept hitting the plug. Do you think I should tear down and check the whole engine or do you think I'm safe running it and trying out the shorter plugs. What would you do if it was yours? Like I said I didn't here any noise or feel any clunking and I did adjust the valves to factory spec now. Oh and do you think I still have a bad head or head gasket beings the valve adjustment was way out of wack or wouldn't that still make that one plug look like crap?

 

[bertsmobile1]

For now I would go with the shorter plug.
If it gives you grief, do not force the plug in but get a plug thread tool , put some axel grease on it & run it down the plug hole.
Remove the tool clean up around the plug hole. fill the cylinder with light oil and crank the engine with no plug.
This will eject any swarf that may have dropped in to to pot.

As for plug thread length, the plug should not have any threads inside the head so you can measure the depth of the plug hole and then compare that to the length of the plug

 

[DevonD]

Went to the John Deere dealer today and got the BMR4A NGK plugs and what a difference in size. The BPR4ES NGK is twice as long. If this shorter plugs are the right ones I cant believe that those other plugs didn't do anymore damage than what I can see. That doesn't say that the inside of the engine is ok I guess, but I hope I caught it in time. The parts guy at John Deere said that the Kawasaki FD620D has 2 different style of heads on them and when people go to buy the maintenance kit for those motors they just grab one beings everything is the same in the kit and not knowing they sell 2 different kits with different spark plug sizes. I also picked up new push rods for the engine too beings they were only a couple dollars a piece. Don't know if they were needed but figured I might as well. I would like to just take the heads off and make sure the valves are good and clean beings the lash was off so much on them, but don't want to tear into anything and spend extra money if not needed. Thanks for the tips on re-threading of the spark plug hole and what to do. Appreciate all the help. Will let you know how I come out on everything here in a couple days.