About O.S #8 plugs!
 

Hi everyone.

I just wanted to share something with you and was wondering if it had happened to you too.


I have an o.s 46 FX that run ok....I used to run it with tower plugs (aka O.S #A3) and one day I just wanted to try an O.S No. 8...the engine performed with gobs of power like with the other plugs BUT....it stopped after about 10 seconds at full throttle ( the engine was properly tuned btw)...it just died....
I looked for all kinds of possible problems...tank, fuel, prop, engine internals...everythin was fine....

Another day I just try again a tower plug and the engine was good again.

The story I just wrote was about 2 years ago...

Today at the field, I helped a fellow to break-in an ASP 52.....and it was the same story....and again..changed to a tower plug, and the engine was running good again....


It is very strange...since the engine idles, transitions and runs wot very well...but soon after the engine just dies.
we fly here between 1650MASL to 2500MASL....but it seems dramatic to me that the plug makes so a strange behavior.

With the tower or A3 plugs I never had any problem...but the #8....is just a no go.


any thoughts?

RE: About O.S #8 plugs!
 

The A3 is a hotter plug than the #8

RE: About O.S #8 plugs!
 

Did it restart? Was it overheated?

I use the OS 8 in basically all my 2strokes from a .46 to a 1.08 and they were great. If it's going from running ok to gobs of power, my guess is you'd need to richen the needle out to the "ok" position...then work on advancing it until it will run through the whole tank

RE: About O.S #8 plugs!
 

I use the #6 or #7 plugs in my OS46AX. In my OS91FX is use the #8

Smaller engines need a hotter plug to run under rich conditions.
 I find the #8 works once youhave the engine tuned for max performance

RE: About O.S #8 plugs!
 

Thanks for the responses.


Yes I know the A3 is hotter, and the main reason I use them is because I used to fly FAI fuel, but it stills works great with 5 to 10% nitro.

No engines weren´t overheated, they restarted right away...and they were properly tuned (about 200 to 300 below max RPM).

I posted this because it seemed curious to me and I wanted to see if anyone had the same behavior?.......
My point is....with the # 8 to keep the engine running it must be exactly on the sweet spot....I couldn´t let the engine run a little richer because it just stopped (for example it died after taking the glow heater) and it gave a very very narrow tunning range.....with the A3 it just run ok no matter rich or properly tuned.....to me with the #8 it just looked strange

RE: About O.S #8 plugs!
 

Did you retune the needles?  If you go from a hot plug like the A3 to a medium plug like the #8 you will be running rich till you retune the engine.

RE: About O.S #8 plugs!
 

Sure I did retune....

I don´t even say I couldn´t get the engine running, I did....just that with the #8 the engine died suddenly at times. and that with the #8 I couldn´t get the engines to run rich....

RE: About O.S #8 plugs!
 

I guess I've always used the Tower Power plug as a replacement and the only OS #8's I've used came in the new OS engines

RE: About O.S #8 plugs!
 

My Tower Hobbies 46 would do that same exact thing on the #8; On the A3 it would run great and could even be rich. I've had other engines that liked the #8 and would not run right on the A3.

RE: About O.S #8 plugs!
 

That's not true at all.

RE: About O.S #8 plugs!
 

Yes it is true. The hot plug requires a richer mixture to quench the heat of the plug and retard the timing. With a colder plug you will have to lean the mixture.

RE: About O.S #8 plugs!
 

what do you refer to as retune the engine? Re setting the LSN and the HSn or just the HSN?

RE: About O.S #8 plugs!
 

Hmm, I checked it out.. it's true.

After all these years I thought it only mattered with the nitro content change to re-tune.

RE: About O.S #8 plugs!
 

I've routinely used OS #8 plugs and recently I've been having problems where I start my plane(s) fly and then on the next flight, I can't get the engine to run once the glow ignighter is removed. Change out the plug and it runs fine. Others at my field have been helping me with the diagnosis, althought I've been flying for 30+ years and they can't explain it either. I been through 6 plugs this flying season and don't really know why. I'm used to having a plug go a long time. Wonder if they've cheapened their materials?? This occurs in well broken in engines. I'm flying mostly OS46FX and OS91FX using 15% nitro in the 46's and 10% nitro in the 91's with 18% lubricant in both fuels.

RE: About O.S #8 plugs!
 

Something has happened to OS plugs?

This is not the first time I have heard this story.

Try a different brand?

RE: About O.S #8 plugs!
 

I'm pretty confident they did change materials or changed their manufacturing process for cost reasons. I'm happy to have bought 50+ os #8 plugs 5 years ago.

edited by blw

RE: About O.S #8 plugs!
 

Try Merlin plugs, his 2003HD works great and lasts a long time.

RE: About O.S #8 plugs!
 

I'm on the same boat with OS changing materials on the latest batch(es) of OS #8s. Guys at our club are constantly complaining about going through them like candy now, unlike in the past. Cutting corners where they shouldn't be, especially at their premium $$! I guess I should look into some tower plugs as well.

RE: About O.S #8 plugs!
 

The Tower plugs are made by OS. The next batch of them will probably be the same as the OS?

RE: About O.S #8 plugs!
 

Very strange,

I was about to start a new thread and ask why my 2 stroke .61 Mutunuc is burning up plugs, and then I came across this thread. I bought a used .61 Mutunuc a year ago and it ran fine all last year. I had installed an old OS #8 that I had laying around. That plug finally gave out and I bought a new one to replace it. It burned out rather quickly. Since then I have burned up about 5 new #8s. Maybe I should try another brand. What brand and number would be a good replacement for the OS #8.

I'm fairly new to this and was wondering what other conditions would make plugs burn out? Will I burn out plugs if the engine gets to hot?

Thanks
Tom

RE: About O.S #8 plugs!
 

I have been using Fireball plugs on my 2 strokes with good results. They are made in USA and were one of the first mfg of plugs.

RE: About O.S #8 plugs!
 

If you knew Aldon Kelly and knew all the quality checks and just plain "know how" he puts into his plugs you would use Merlins.
He is truly a master of manufacturing glow plugs, in fact you may have used his plugs in OEM applications without knowing it.

RE: About O.S #8 plugs!
 

Years ago I tried some OS plugs, but they just didn't work well at all, very short lives to them.
I almost universally run FOX glow plugs anymore, and I have excellent results with them. I thinki still have some Rossi's and K&B plugs. The only OS plugs I have are the ones that came with the four cycle engine engines I happen to have. when they burn out, i install Fox Miracle plugs instead.
But when I was pylon racing I was trying out and using a number of more exotic glow plugs at the time. But heck even then the venerable Fox glow plug would wind up being usable even then too. But I think if I remember correctly, the Rossi plugs gave some better RPM results in some cases.
I remember using some GlowBee plugs way back then too. The GlowBees worked OK, but I sort of got tired of replacing them after every heat. it was getting expensive. The Glow Bees had a large exposed element wound in a spiral shape so it was more fragile. So in racing you got more RPMs but the glow plug tended to die fast. So you had to put in a new one for every race.

RE: About O.S #8 plugs!
 

From the OS 46 FX manual:

"Since the glow plug and fuel combination used
may have a marked effect on performance and
reliability, it would be worthwhile to experiment
with different plug types.
Recommended O.S. plugs are Nos. 8, A5
and A3. Carefully install plug finger-tight,
before final tightening with the correct size
plug wrench"

On starting ...
2–Glow Plug
O.S. No. 8 glow plug is fitted to the engine.

Sounds like OS realized that the answer to "which glow plug?" is "it depends".

RE: About O.S #8 plugs!
 

The McCoy MC-9 is a good all around 2 cycle plug. I used it all the way from the OS .46 FX to the OS .91 DF