My 066 eats spark plugs

Scott03 · October 22, 2016, 12:57:50 AM

Is it a 'Red Eye'. Though I have not seen one I have read that their coils used to play up
Does it have an aluminum or polymer flywheel? I have seen several polymer flywheels that had their centers twist a couple of millimeters, enough to retard the ignition timing, which could cause spark plug fouling.
Before you start wasting money on spark plugs, try this on the fouled ones. Chances are you might be able to revive them.
My smart phone was a bit out of focus so the differences between the 'Before' (pic 01) and the 'After' (pic 05) may not be quite noticeable unless you look carefully.

joe_indi, it's an aluminum flywheel. What's a Red Eye?

None of the dead plugs are fouled, if I can figure out how to put up a photo you can see for yourself (what looks like carbon across the gap is just the angle of the shot - the gap is clean). I don't think they are defective either, something is killing them.

Scott03 · October 22, 2016, 01:05:13 AM

A couple of comments on the photo above: This plug was installed brand new and died after only 2/3 tank of gas, it doesn't work hot or cold. The colors of the insulator are not due to shadows or angle of photo. The light gray part must be a hot spot, and the dark part is carbon.

ZeroJunk · October 22, 2016, 01:23:04 AM

Maybe somebody else has already asked, but do you have another piece of equipment you can put the plugs in that quit working in the 066 to see if they will work there?

The Red Eye will have an extra wire coming from the coil to a red light on the side of the carb box. It was used as a tuning feature. Wasn't reliable because the RPM that lit the red light changed over time.

If it goes bad you will have to find an aluminum flywheel that has an X and Y slot if it didn't come with one so you can use a standard ignition module.

Scott03 · October 22, 2016, 01:57:49 AM

ZeroJunk, that was good advice! I have an MM55 tiller, swapped the "dead" plug into it, and it worked! But it still won't work in the saw, so there really must be gremlins in there. I'm going to take it in and let the pros look at it, and pay up for their expertise.

The saw has an outline on the housing for where the red eye would go, and there were instructions for it in the manual, but mine doesn't have it. I bought it mid-90's, maybe they decided to get rid of it by then.

Ada Shaker · October 22, 2016, 03:32:42 AM

Interesting to see something is causing your spark plugs to increase its internal resistance by 25%. The only thing I can think of that will do this is a higher than usual kv from the coil (which is generally unlikely unless you've changed the flywheel with increased magnetism) or heat is killing off your spark plugs (+ve temp coefficient of resistance), the higher the heat, the higher the resistance. Would be interesting to see the difference between a hot spark plug that has just failed and a cold one. Check to make sure your saw isn't running e excessively hot first.

Al_Smith · October 22, 2016, 04:06:46 AM

Well I'll me a monkys uncle.I checked it out and sure enough you can check a plug with an ohm meter .Never knew that,never had a plug fail completely .I've had them foul on old oil burning engines though .So I guess an old dog can learn a new trick,arf.

I've got an old Champion spark plug sand blaster that's probably about as old as I am .It will clean a fouled plug slick as a whistle.

Ada Shaker · October 22, 2016, 10:23:31 AM

Just bear in mind that not all spark plugs are created equall. Not all have a high internal resistance.

ZeroJunk · October 22, 2016, 11:24:24 AM

Not sure why they put a resistor plug in a chainsaw to start with.

Scott03 · October 22, 2016, 01:40:14 PM

Quote from: Ada Shaker on October 22, 2016, 03:32:42 AM
Interesting to see something is causing your spark plugs to increase its internal resistance by 25%. The only thing I can think of that will do this is a higher than usual kv from the coil (which is generally unlikely unless you've changed the flywheel with increased magnetism) or heat is killing off your spark plugs (+ve temp coefficient of resistance), the higher the heat, the higher the resistance. Would be interesting to see the difference between a hot spark plug that has just failed and a cold one. Check to make sure your saw isn't running e excessively hot first.

Ada, now I'm wondering if it is indeed running hot, and hurting but not killing the plugs, and also has a weak coil that won't fire a damaged plug with higher resistance, but will fire a new one, at least until that one gets overheated, too. Since the supposedly dead plug works in my tiller, maybe it means the tiller's coil is good and has enough power to fire even the higher-resistance plug. Anyway, it's in the shop now and they have the whole story, so we'll see what they can find. I'll let you all know what happens, it's supposed to be ready Monday.

HolmenTree · October 22, 2016, 03:21:26 PM

When I bought my 066 Arctic red lite around 1992 when it was first introduced, about a month later my Stihl rep Dave Gordon got me the upgrade module to disable the red lite as they had problems with that new digital technology.
I can't remember if I changed the aluminum flywheel.
Don't remember what the outcome would have been if the upgrade wasn't made.
Bosch plugs are as good as a plug you can buy.

Ada Shaker · October 22, 2016, 05:50:18 PM

Quote from: Scott03 on October 22, 2016, 01:40:14 PM
Quote from: Ada Shaker on October 22, 2016, 03:32:42 AM
Interesting to see something is causing your spark plugs to increase its internal resistance by 25%. The only thing I can think of that will do this is a higher than usual kv from the coil (which is generally unlikely unless you've changed the flywheel with increased magnetism) or heat is killing off your spark plugs (+ve temp coefficient of resistance), the higher the heat, the higher the resistance. Would be interesting to see the difference between a hot spark plug that has just failed and a cold one. Check to make sure your saw isn't running e excessively hot first.

Ada, now I'm wondering if it is indeed running hot, and hurting but not killing the plugs, and also has a weak coil that won't fire a damaged plug with higher resistance, but will fire a new one, at least until that one gets overheated, too. Since the supposedly dead plug works in my tiller, maybe it means the tiller's coil is good and has enough power to fire even the higher-resistance plug. Anyway, it's in the shop now and they have the whole story, so we'll see what they can find. I'll let you all know what happens, it's supposed to be ready Monday.

Sounds feasible, be interesting to find out what the problem was and what caused it. Do keep us in the loop.

Ada Shaker · October 22, 2016, 05:53:17 PM

Quote from: HolmenTree on October 22, 2016, 03:21:26 PM
When I bought my 066 Arctic red lite around 1992 when it was first introduced, about a month later my Stihl rep Dave Gordon got me the upgrade module to disable the red lite as they had problems with that new digital technology.
I can't remember if I changed the aluminum flywheel.
Don't remember what the outcome would have been if the upgrade wasn't made.
Bosch plugs are as good as a plug you can buy.

Probably a few blacken eyed stihl reps walking around the place most likely. :D

Pine Ridge · October 22, 2016, 10:00:34 PM

Try a different brand spark plug and see what happens, I had a similar problem a few years ago , same brand plugs that you mentioned.

Scott03 · October 23, 2016, 02:25:46 AM

Quote from: Pine Ridge on October 22, 2016, 10:00:34 PM
Try a different brand spark plug and see what happens, I had a similar problem a few years ago , same brand plugs that you mentioned.

Not a bad idea. HolmenTree says Bosch is among the best, and they do seem to make good stuff in general. But even the best can come up short once in awhile. Like the RedEye thing with Stihl. Also, I had a silly problem with the 066 a few years back. It's a magnum, which means they hot-rodded it to bump up the power-to-weight ratio. But someone forgot to beef up the crankshaft to handle that extra power, so one day I was running it hard, ripping with an Alaskan Mill, and it broke. The shop guys knew all about it and were surprised mine hadn't broken sooner. I guess I hadn't run mine as hard as the loggers around here (I'm in Oregon) so it lasted a bit longer. They fixed it free, which was nice, but it was a dumb thing for Stihl to have overlooked in the first place.

We'll see what the mechanic says when I get the saw back, and go from there.

Scott03 · October 23, 2016, 02:30:38 AM

Quote from: HolmenTree on October 22, 2016, 03:21:26 PM
When I bought my 066 Arctic red lite around 1992 when it was first introduced, about a month later my Stihl rep Dave Gordon got me the upgrade module to disable the red lite as they had problems with that new digital technology.
I can't remember if I changed the aluminum flywheel.
Don't remember what the outcome would have been if the upgrade wasn't made.
Bosch plugs are as good as a plug you can buy.

That thing has seen some action! Looks like yours has a metal air filter housing, mine is plastic.

Al_Smith · October 23, 2016, 04:03:24 AM

I wonder why they would use resister plugs on a chainsaw? The intent when they first came out was electronic noise suppression .Prior to ii caused it caused peoples televisions to go bonkers .Ha I had a 1959 Pontiac that drove my then girl friends father nuts .

Ada Shaker · October 23, 2016, 04:58:02 AM

Quote from: Al_Smith on October 23, 2016, 04:03:24 AM
I wonder why they would use resister plugs on a chainsaw? The intent when they first came out was electronic noise suppression .Prior to ii caused it caused peoples televisions to go bonkers .Ha I had a 1959 Pontiac that drove my then girl friends father nuts .

The carbon ignition leads worked under the same principle. I also thought that was what the ignition filter capacitor was for, to help filter out noise produced by arching, which has a pretty wide band width. Now we have capacitors, carbon leads and resistive spark plugs working in unison with an inductive coil. I sometimes wonder about the LCR circuit and if it has something to do with resonant frequencies as th3 chainsaws run wot.

ZeroJunk · October 23, 2016, 08:26:21 AM

I knew they would wreak havoc on an AM radio in particular, but didn't realize the range of it would be enough for a saw to interfere with anything nearby.

I don't suppose they hurt anything, he has something else going on, just not sure what.

Could be the compression has gotten on the low end and only a fresh plug will keep it going. Or, could be the condenser part of the coil has opened.

A 000 400 1300 can be bought really cheap off eBay. I would have tried that first.

Hilltop366 · October 23, 2016, 09:05:36 AM

Its unlikely in your case but often over looked problem with small engines that are finicky is the flywheel/coil gap, a little extra gap can weaken the spark making it hard to start.

HolmenTree · October 23, 2016, 10:57:25 AM

Quote from: Scott03 on October 23, 2016, 02:30:38 AM
Quote from: HolmenTree on October 22, 2016, 03:21:26 PM
When I bought my 066 Arctic red lite around 1992 when it was first introduced, about a month later my Stihl rep Dave Gordon got me the upgrade module to disable the red lite as they had problems with that new digital technology.
I can't remember if I changed the aluminum flywheel.
Don't remember what the outcome would have been if the upgrade wasn't made.
Bosch plugs are as good as a plug you can buy.

That thing has seen some action! Looks like yours has a metal air filter housing, mine is plastic.

Yep metal cover. My saw is the very first run of the 066's onto the market. The crankshaft never failed and the cylinder has never been removed and it's over 24 years old.
I always religiously used 40:1 Stihl Premium mix (Castrol Super 2 Stroke) with premium gas. It has bucked and noodle split tons of cords of firewood. Milled thousands of feet of lumber with the original 28" bar.

ZeroJunk · October 23, 2016, 01:03:13 PM

I think it was from sticking the nose in to something running wide open and slamming the brake shut on the clutch with the flywheel saying wait a minute. Among other things I am sure. Something an experienced user is less likely to have problems with I suspect.

Ada Shaker · October 23, 2016, 06:06:15 PM

Quote from: ZeroJunk on October 23, 2016, 08:26:21 AM
I knew they would wreak havoc on an AM radio in particular, but didn't realize the range of it would be enough for a saw to interfere with anything nearby.

I don't suppose they hurt anything, he has something else going on, just not sure what.

Could be the compression has gotten on the low end and only a fresh plug will keep it going. Or, could be the condenser part of the coil has opened.

A 000 400 1300 can be bought really cheap off eBay. I would have tried that first.

It has always been known that an uncontrollabe electrical arc of any nature produces RF with a highly variable bandwidth. Electrical motors are quite often the worst culprits. Keeping in mind that the minute signals are picket up by the antenna and amplified through the devices amplifiers stages. A combustion engine may not be so bad as the arc is completely surrounded by metal. As of late these issues have become less of a problem due to good filtration at both the source of thr arc and at the receiving end, service stations still request that you turn off your mobile phone when refuelling though.

ZeroJunk · October 23, 2016, 07:31:50 PM

I have been a licensed amateur radio operator for about 35 years, so I understand the concept. But, I was thinking the resistor plugs were designed to limit interference to AM radios in cars where the wanted signal and unwanted interference are amplified equally. In todays technology it may interfere with the onboard computers etc. FM and digital are not effected to the same extent at all. Plus antennas are a two way street, so I can't see a chainsaw bothering anything ever even in the AM days for more than a few yards maybe.

But, it could be that all they use are resistor plugs anymore for simplicity or other reasons that don't occur to me. May interfere with the electronics in the ignition module itself.

The reason is not RFI from chainsaws.

bill m · October 23, 2016, 08:29:25 PM

Almost all areas of the USA have regulations on radio interference, including from internal combustion engines. Hence the reason for resistor plugs being required.