why are plugs failing?

[rbig]

I've got several mowers with twin cyl engines, as well as a couple with single cyl engines. Seems like I frequently have plugs go bad.

When I pull 'em and look at them, they show pretty normal, and no signs of heavy fouling like you'd expect to see with plugs that quit working. Cleaning the things doesn't seem to help. New plugs get me going again.

What I do is keep a good supply of several changes of each kind of plugs I use on hand. Fortunately, plugs are relatively inexpensive, so it's more of an annoyance than a real problem.

Has anyone else experienced this scenario? I've wondered what is causing the failures.

[rockytopp]

I do believe that as with many things in the repair work, the quality of control has gone out the window. I find this in auto parts as well. Seems that mexico and other parts that are imported are made to make the manufactur money and control is the last thing they care about. Parts that used to be rebuildable are now throw away, so the pride and care that once was standard has been lost. This is a sad situation but I am afraid here to stay.

[CCWKen]

You didn't say how long they're lasting. I replace plugs on the tractors twice a season. (Just started last week here.) The push mowers, trimmers and saws get a set per season. I could probably push the tractors to a set a season too but the power and economy take a real hit towards the end of the season. It's worth it, in fuel savings, to keep the engines running at peek power.

The problems with small engines are heat and fuel delivery. Neither are controled very well and this takes a toll on spark plugs. Like you say, they are cheap but they can give a tired engine new pep in an instant. Sharp blades and new plugs save a lot of gas! When you go through about 50gal. a month, a 30-50% savings adds up in a hurry! Especially at $2.00 a gallon.

[sawman65]

i bet you have kawasaki engines dont you???

[rbig]

Most of our engines that are having plug failures seemingly too often are Kawasaki

[DRM Ventures]

my Kawi's will foul plugs...especially in cool weather.......

Derek

[Guthrie&Co]

i would check my fuel source. might want to try a diffrent fuel source

[Mower Man]

Kaw's coils aren't the best. Quietly, their upgrading.

Choke settings MUST BE done as per the instructions using a 'set pin', and followed line by line.
If not done as per instructions choke setting will be off.

If using an "associated choke" thats when throttle & choke are combined...it's even more important.

Recoil starts have been somewhat balky in cool-colder weather.
Using a good 10-30W makes pulling easier....higher RPM which creates better coil induction....for higher voltage.

Check oil for gas in it. When pulling over alot, and it doesn't start fuel can thin out the crankcase oil.
Use the sniff test. If suspected.....carefully away from any fuel source, using a match-lighter stroke the dip stick. Stroke---not too much, not too close.
If flame gets larger, or oil 'puff' ignites, there is fuel in the crankcase.

Two starters are available.
Standard torque & high torque.

Standard uses a seperate starter solenoid NOT mounted (piggybacked) to the starter. Follow Positive (Red) cable from battery to a black colored object that has 3-4 terminals.
Have seen these solenoids from water-moisture get inside---corrodes contacts which reduces electrical flow. R & R, coat terminals with dielectric grease after assembly, and use boots on BOTH terminals if they point straight up.

High torque is usually a silver colored large round shaped Bendix style mounted on the starter. It provides about 200 more starting RPM.
It's an option that costs alot more, so many mower companies don't spec it.

Kawa's should have valve clearances checked as per Maintenance schedule. Very important to starting, and operational efficiency.

Have seen fuel deposits (hard crystalline mustard color) form on the fuel bowl float jet, and metering jets.
Sometimes using a engine fuel system cleaner helps.
Sometimes only physically removing works.

[topsites]

I've got several mowers with twin cyl engines, as well as a couple with single cyl engines. Seems like I frequently have plugs go bad.

When I pull 'em and look at them, they show pretty normal, and no signs of heavy fouling like you'd expect to see with plugs that quit working. Cleaning the things doesn't seem to help. New plugs get me going again.

What I do is keep a good supply of several changes of each kind of plugs I use on hand. Fortunately, plugs are relatively inexpensive, so it's more of an annoyance than a real problem.

Has anyone else experienced this scenario? I've wondered what is causing the failures.

YEAH! I found out you need to make sure you get the special lawn-mower 2-cycle plug. In my case I was using automotive plugs made for cars which cross-referenced at the auto-parts store, and these things kept fouling.
Make sure when you go to the auto-parts store, you tell them it's for a lawn-mower as the plug will cross-x to a car-plug when they look it up on the computer and that is wrong.

Funny thing ... The auto-plug's thread and firing element is black while the 2-cycler is all silver in metal color.

[Teiman]

Mower Man

Thanks, just bought a used machine with a 23 Kaw FH
(270 hrs) it blows tons of whiteish smoke for about 40 seconds
on start up, smoke smells like fuel not oil. Choke off as soon as it fires, and
the CC oil definitly stinks of fuel. Seems to burn clean after a minut or two.

I think you gave the answer to my problem, No ?

[rbig]

Great info. I think you have a really good point. I've been using automotive plugs.

[Mr Dane]

Stay Away From Autolite Spark Plugs !!!!!!!!!!!!!!!! They Are Not Made For The Heat Have Been In Several Arguments About This But When I Use About 500 To 700 Spark Plugs A Year I Know Which Ones Are Good And Which Ones Are Bad

[Oldtimer]

For the last 5 years we have been using Bosch both in the shop and over the counter. We have had the best service from Bosch. They are a bid pricey but we don't get spark plug complaints any more.

[fixer67]

Are the plugs the right heat range? Are the engines being ran at full thottle when being used. Trying to mow with the engine at less than full thottle will foul plugs quick. I had a man that fouled out plugs in his rider every week. He was trying to cut at half thottle because he did not want to throw the grass all over the place and he also though the mower would last him longer if he ran it at "idle" while mowing. Clogged air filters will foul plugs as well. You say the plug looks good but will not fire, this may be what is called "carbon tracking". Carbon builds up a thin film and causes a track from the tip the threads and shorts out the plug. Carbon tracking is a sign that the plug is too cold and you need to use the next higher heat range.

[BODIDDLY]

this thread just helped me out....thanks,ive been using autolite on my kaw engine.every time it wouldnt start i just replaced the spark plug.gets annoying doing it every other week.ill try a better spark plug and see what happens.also ill check my oil to see if gas is in it....

[blue_steel2]

I agree with Mr Dane. I had Autolites in a Ford Escort around 1990 (I realize we are talking about mower engines, but I had a nasty flashback when I saw Mr Dane's post). The engine began to run rough and I pulled the plugs. The ceramic insulators were gone on 2 out of 4 and the plugs were only a couple of months old. I pulled the head and the ceramic had broken a couple of valves and left dents in the head. My buddy resurfaced the head, replaced the valves and I put it back together and called Autolite. They wanted to see the plugs and sent me a package to return the parts ASAP. I was nervous about sending them the "evidence", but they sent me a letter a week later saying they X Rayed the plugs and the ceramic was found to be defective. Hairline cracks were in the ceramic and traced back to when they were manufactured. The heating / cooling cycles of the engine made the ceramic separate further until it fell into the cylinder. They asked me for an estimate of the time and expense for me to repair the car and sent me a decent sized check. Signing and cashing the check freed them from any responsibility that their product caused my problem. Since that time, I have always tried to stick with NGK or Champion, but NGK always seems to last longer. Also, Motorcraft brand is mfgd by Autolite.

[STINGRAY310]

Check oil for gas in it. When pulling over alot, and it doesn't start fuel can thin out the crankcase oil.
Use the sniff test. If suspected.....carefully away from any fuel source, using a match-lighter stroke the dip stick. Stroke---not too much, not too close.
If flame gets larger, or oil 'puff' ignites, there is fuel in the crankcase.


What should you do if you have gas in the oil, what is the cause of this and how do you prevent this and what damage could be cause by this?

Thanks,
Stingray