Thread: Rather Odd Sparkplug Occurance

Had a funny one the other day. This falls under my favorite saying "Never Overlook The Obvious". This didn't happen on a saw but it probably could and this is why I'm passing it along. The machine is lawnmower with a 5.5HP Honda motor. About a week and a half ago I needed to mow the lawn so I gassed up and started it up. Started fine but after about 20-30 sec. it quit, no skipping or stumbling just stopped. Gave it another pull, started right up ran excellent same amount of time and stopped. It did this as many times as I wanted to start it. Didn't matter if was at idle or wide open it would run fine and stop. So I got out the tools pulled the sparkplug and grounded it, gave it a pull, nice blue spark. OK ;says I, an obvious fuel issue. Pulled the drain plug and drained the bowl. Gas looked OK, no water or crap so I put the plug back in and pulled it over started right up ran 20-30 sec and quit! Pulled the carb, took it all apart, blew it out, everything seemed fine so I put it back together, started right up annnnd 20-30 sec it quit. Pulled the carb again and the fuel tank. Drained and washed out the tank, checked the fuel line and petcock, all OK. Took the carb apart again and did notice that the main jet was loose and had moved down some in the tube it screws into and was partially obstructing the fuel inlet from the bowl. AHHA says I!! There is the problem. Removed the jet and emulsion tube and checked for any dirt etc. and put it back together. Confident I had the situation well under control but by now it was dark I decided to mow the lawn the next evening.
Next day I filled the tank, gave her a pull started right up....you guessed it, ran 20-30 sec and quit. Needless to say I was about ready to set fire to to this jap mower from hell. Didn't get the lawn mowed but the wife and I went on vacation for a week had a great time but when we got back the damn lawn looked like the Munsters lived there. So Mon. I took the carb apart one more time hopeful that I had missed something the first 3-4 times I had it apart. One thing I had thought of was to check and make sure the bowl vent wasn't obstructed in some way. NOPE everything was in good order.
I came in defeated and angry and had a beer and then decided it had to be the coil......so I got on line and searched the Internet for 5.5 HP Honda motors well a coil for a 5.5 is around $50.00 + shipping so I kept searching. I eventually ended up at an OPE website/forum that concerned itself with lawnmowers and snowblowers and such. In a few minutes I had found a fellow with the exact same trouble I was having. He had found two previous posters that also had the same trouble. all with 5.5 HP Hondas. He did what they did and bought a new NGK plug and the problem was gone. So yesterday I went to the local parts store and purchased a brand new NGK for a total of $2.19 and went home and mowed the lawn.....!!!!!!

NEVER, NEVER, EVER Overlook The Obvious!!!!!

Now I know a lot of you guys are thinking "Hell I'd have done that first off"

Well perhaps I should have but I have bought so many parts saws and no mater what is actually wrong them they about all have a brand new plug installed that never was run. I probably have 2 doz new Champions that fit the older Jreds. I'll never have to buy a plug again for those old guys!!

In my own defense, I have never had a plug do what this one did. They are either fouled, worn out, won't start or won't run without skipping or whatever erratic behavior they exhibit. Never had one start and run the motor perfect and then not. Never had any other Honda motors either.

The end result though is that I over thought the problem and OVERLOOKED the Obvious!!

Sorry this is such a long post but perhaps it may help someone else not over think a problem.

I had something similar but with a B&S mower engine.
I could start and mow but as soon as I shut it off to move something in the yard it would not restart.
Spark plug showed spark, checked shear key, cleaned carb, etc.
Nothing fixed it.
I would tape the shut off bar to the handle to mow the yard, then cut the tape to shut the engine off.
For some reason I put the old original spark plug back in. Then it ran fine and restarted with ease.
I had put in a new spark plug that season. It was a Champion EZ-Start model plug.
Now I stick with whatever plug the manual recommends on all my engines.

Same story here. I had changed the plug early this spring. Had run the mower several times. Then one day went to start it ran 20 to 30 seconds and died. Started right back up. Kept dying after 20 to 30 seconds. Changed the plug finally after kicking it many times and cursing. Problem solved.

I have had similar problems over the years with bad plugs in small engines,
try to keep spares for mine, sometimes will buy new plugs and save known old good ones for spares in box new one came in, saves a lot of unneeded troubleshooting time; if in doubt, change the plug.

Well the good news is I'll keep a new spare plug around for this motor and won't hesitate to change it out the first time it exihibits these symtoms again. LOL!! I tell ya putting that carb back on takes three hands and alot of patience. There are 8 pieces including gaskets, two linkages, a spring and two hoses that all have to be in place before the two bolts that hold the whole mess on can be started. It's a real PITA but after you do it a few times you get good at it LOL!!!

I hear ya for sure, but my hard head keeps telling me its going to cost more than $2.19. REJ2

cantdog I had the exact same experience with my honda harmony push mower last year, and I got tired of messing with it. It was in good shape otherwise so I gave it to a friend. I talked to him a week or so later, he tried all the same things I did with no luck. Finally his dad(mechanic 50+ years) says put a new spark plug in it. Now it runs like a top and he loves it. Why I never tried that, who knows, but your right never overlook the obvious.

...the saw would fire up if hot but if started with choke would more often than not flood and stop.

The last owner told me that he'd got tired of it so bought a Stihl. I got it home and it wouldn't fire so out with the plug and it had a brilliant blue spark. After several problems with cold starts I chucked a spare plug in it and it's never looked back.

Only then did I have a really close look at the plug and discover a crack down the centre insulator. If it got wet (i.e. when starting with choke), the spark would track down the crack and not fire. It was fine when hot.

So I got a 1-owner 2101 which has only been used on a farm to cut oaks for cheap.

Originally Posted by jonseredman

cantdog I had the exact same experience with my honda harmony push mower last year, and I got tired of messing with it. It was in good shape otherwise so I gave it to a friend. I talked to him a week or so later, he tried all the same things I did with no luck. Finally his dad(mechanic 50+ years) says put a new spark plug in it. Now it runs like a top and he loves it. Why I never tried that, who knows, but your right never overlook the obvious.

The Honda 5.5 may be prone to this type problem it seems. I have no idea why. It acted for all the world like a fuel issue (10% Ethanol in Maine)

I examined the plug closely and couldn't SEE any cracks in the insulator as Gredford said but they must there and as the plug warms must expand and allow a path to ground somewhere. At least for once it was a cheap fix!!LOL

I had one other weird plug failure once. Happened on a series IIA Landrover. One foggy morning it was warming up with the throttle set for a high idle. I was loading the saws, fuel, oil, choke chains etc. in the back when all of a sudden she coughed and started running on only one cyl. putt-putt-putt!! So thought cracked distributer cap. Had new spares so replaced it, no change. Cleaned and regapped the points, no change. New wires, no change. Pulled the carb and checked fuel pressure cleaned and kitted carb, no change. Finally found three plugs that had cracked their insulators simultaneously!!! The only explanation for this I could come up with was, due to the extreme humidity that morning and warming up at high idle the throttle plate had developed large amount of ice build up and when it let go and was inhaled the ice or water hit the hot ceramic insulators and cracked three at once. Another few hrs of (paying) work lost to trying to fix something that wasn't broken!!LOL!!

On the other hand she got a good tune up!!!

I had a couple retarded plug problems over the years...Bought a mower from a neighbor at the cabin...they retired and moved up there so was selling some equipment since they had double for cabin and house...anyway, he started it up for me to listen, and everything was fine. It was fall at this point, so I didn't need to use it till spring. Come spring it wouldn't start for the life of me. After weeks of messing with it on and off, problem ended up the piston kept closing the gap of the plug somehow, even though it was the same plug I heard it run with. I tried a couple new plugs with the same model number on it, etc. same thing, gap closes off. I grabbed the plug from my 029S since it was the only other plug I had around and the saw was in pieces anyway. It fired right up and ran like a dream. The saw plug had a much shorter threaded shaft before the electrode was much longer...What I still cannot figure out is how it ran just fine before I bought it...