Glow engine woes... (Full Version)

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acerc -> Glow engine woes... (8/19/2012 7:37 PM)

A friend has asked me a question that I can't answer. How about you guy's. The engine is a Magnum 120 4stroke. When started upon removal of the glow plug the rpm's increase. What would cause this?



Cobra1 -> RE: Glow engine woes... (8/19/2012 8:16 PM)

The only thing I can imagine is that the timing changed for the better. When using the glow battery the timing was too far advanced, pre ignition. When removed it retarded and more energy used to push piston down instead of trying to keep it from coming up.



jeffie8696 -> RE: Glow engine woes... (8/19/2012 10:02 PM)

Glow heat affects timing, if the glow plug is too hot the ignition will occur too soon and lower the power output. This can also be affected by higher nitro and higher compression. With the glow igniter attached you are artifically making the glow plug hotter.



Cub Flyer Fresno -> RE: Glow engine woes... (8/19/2012 11:00 PM)

Hey guys, I'm the friend acerc is referring to.   I'll give you a little more information:

First of all, as stated, I have a Magnum FS-120.  It will only run at idle with the glow igniter attached.  It runs well at around 1/2 throttle and higher, but below that, will die.  At the lower RPM's, when the igniter is removed, is when the RPM's increase.  I've tried opening the low speed needle until it was too rich and would load up quickly.  I leaned it up until it was too lean to run at idle.  Right in between is where it runs best, but again, with the igniter attached.  There is no happy medium without it.

I agree with both Cobra1 and jeffie8696.  That's the only thing that made since as to why it would speed up.  However, it won't keep running unless I'm at 1/2 throttle or higher.  I have considered running with an On Board Glow, turning on under 1/2 throttle, but I'd rather fix the problem instead.

So, with that said, does anyone have any other suggestions?

By the way, thanks Ace for getting this started!

Take care,
David



P-40 DRIVER -> RE: Glow engine woes... (8/20/2012 12:23 AM)

Check your cam timing, your valve lash and the Oring at the intake manifold to carb for proper seating, also check your idle mixture screw. Probably cam timing, mark should be inline with pushrod tubes or straight down depending on engine at TDC. Put a fresh OS F plug and try different fuel also. The Magnum 120 will idle all day at 2000 rpm if properly tuned and broke in and turn 8000-8500 rpm peaked with MA 15/8 prop.



Cub Flyer Fresno -> RE: Glow engine woes... (8/20/2012 12:30 AM)

Thanks P-40.  I'm running the MA 15x8 now and the same fuel mix as the guy who owned it before me.  He recently examined the engine himself, so I'll relay this info to him to see if he checked all that before I tear into it.

Hey, sorry Ace!  Didn't mean to hijack your thread!  [:D]

Thanks again!
David



freakingfast -> RE: Glow engine woes... (8/20/2012 12:50 AM)

This could just be a bad glow plug. The plating on the element is gone or the element is contaminated. As already suggested, try a fresh OS "F" plug before anything else.



Cub Flyer Fresno -> RE: Glow engine woes... (8/20/2012 12:54 AM)

Oh, forgot to say I already tried that.  It ran the same as with the original plug.  And I did get the OS "F" plug as well.  Guess it wouldn't hurt getting another just in case it was two bad plugs in a row.  Hmmm...



Hobbsy -> RE: Glow engine woes... (8/20/2012 2:09 AM)

When the timing changes for the better when the glow power is removed, that is an indication that it is too lean. If it were too rich it would slow upon removing the glow power. Try richening the LS needle about .5 turn, then peak the HS needle and see how it does. Then go back and reset HS needle for your normal setting.



Cub Flyer Fresno -> RE: Glow engine woes... (8/20/2012 2:13 AM)

Thanks Hobbsy, I'll give that a try... in a day or two.  I'll let you know what happens.



KW_Counter -> RE: Glow engine woes... (8/20/2012 3:27 PM)

Does the original owner live near you?
I had a similar sounding problem after moving from the
Imperial Valley, below sea level, to Lake County, above 1,000 feet.
When I switched from 10% nitro to 15% the problem was solved.

Good Luck,
KW_Counter



Cub Flyer Fresno -> RE: Glow engine woes... (8/20/2012 3:48 PM)

Thanks KW_Counter.  Yes and no, but the important part is we live at pretty much the same elevation.  However, the blend of the fuel (he mixes his own) may have something to do with it.  I'll check to see what % this is and maybe try some 15% out just to see if that does the trick.  A hotter burn just might work, makes sence anyway.  Once again, I'll let you know.

Take care,
David



Cub Flyer Fresno -> RE: Glow engine woes... (8/20/2012 7:01 PM)

]

I checked with the original owner, it is 15% fuel.  We're now thinking that since it had been sittting awhile, maybe the intake O-ring could be bad.  I may get a kit just to fix that.  Does anybody know where I could get an O-ring other than from Global Services (not that they're bad, just like to find a local source)?

Thanks,
David



jeffie8696 -> RE: Glow engine woes... (8/20/2012 7:23 PM)

Auto parts store?
As an aside, I am not a huge fan of Magnum engines but I have a 52 FS on my Escapade and have flown it for several hours now with great success.
It took a long break in but it runs like a champ now. It lacks the refinement of my Saitos but it also lacks the price tag.
I purchsed a Saito 62 to replace it but to tell the truth I am so happy with the Magnum 52 that I am dragging my feet swapping it out (that and I am a lazy SOB lately).
I landed some 30% nitro fuel for cheap, and the 52 LOVES it  !!



Cub Flyer Fresno -> RE: Glow engine woes... (8/20/2012 9:15 PM)

From what I've heard (may not be true) the Magnum will run on straight nitro, not sure about that!

I would agree with the price tag!  And, a side note, from what I've heard (here we go again) Magnum is made by OS!  (Thanks for that info Ace!)

Anyway, I'd like to eventually replace this with a gasser to save money in the long run.  But for now (until I can save up the money, maybe in a few years [:@]) I'll keep this one running.  Or I guess I should say "get this one running"!

Take care,
David



landeck -> RE: Glow engine woes... (8/20/2012 9:44 PM)

Magnum Engines are clones of older OS engines made in China. I just went blank on the manufacture-old age.[:D] They are good engines and are great for the price.

Bruce



P-40 DRIVER -> RE: Glow engine woes... (8/20/2012 11:19 PM)

You can use high temp gasket sealent ( the orange stuff) if you don't want to fiddle with getting the carb Oring. worked like champ on my 120.



blw -> RE: Glow engine woes... (8/21/2012 12:23 AM)

I deleted a childish comment and had to also delete a couple of reasonable replies since they had quotes of it.



Ernie Misner -> RE: Glow engine woes... (8/21/2012 6:01 AM)

Did you mean you heard a Mag. could run on straight methanol? (not nitro!)

They slow down when you remove the glow driver if it needs more nitro. So speeding up could indicate needing less nitro possibly.



jeffie8696 -> RE: Glow engine woes... (8/21/2012 6:39 AM)

There is no reason it wont run on FAI fuel, but how well is another story.



heavydriver -> RE: Glow engine woes... (8/21/2012 8:28 AM)

The manufacture of Magnum , ASP and some Thunder Tiger is Sanye Motors. These motors are great sport motors that put out plenty of power for the average guy. The designer of these motors worked for OS and they had an ugly parting of ways so the story goes. He took his designs to Sanye as a parting shot. I have quite a few of these motors and i've found that they like 10-15% nitro with some castor (Omega) and a good quality OS F plug. They run like clockwork on that combo. Some guys like to bad mouth them and say they're no good and should buy OS only. Ya, the machine finish is not OS quality, but that cosmetic stuff doesn't make any difference how they run if they're set up correctly. -sorry for bad sp and grammer-new ipad user



pe reivers -> RE: Glow engine woes... (8/21/2012 10:22 AM)

apart from the plug heat range and mixture issues, idle also may be unreliable when the carb is not clean, down around the needle tip.
15% nitro fuel should give reliable idle unless the engine is mounted inverted. In that case adding idle glow will allow lower idle rpm.



Sport_Pilot -> RE: Glow engine woes... (8/21/2012 1:27 PM)

quote:

I wouldn't think someone would pay monthly storage charges unless there was quite a bit of valuable items inside.


That is why the guys running low nitro will often use very hot glow plugs.  Unless it was made for no nitro then you may have to use a cool plug.



Sport_Pilot -> RE: Glow engine woes... (8/21/2012 1:30 PM)

quote:

The designer of these motors worked for OS and they had an ugly parting of ways so the story goes. He took his designs to Sanye as a parting shot.


No, Sanye simply bought a few OS engines and measured all of the parts and did some hardness testing, etc. and copied them.  The story you mentioned was that the designer went to Thunder Tiger.  That company then made original designs that were very similar to OS but not exact copies, thus many parts do not fit. 



Sport_Pilot -> RE: Glow engine woes... (8/21/2012 1:34 PM)

quote:

Ya, the machine finish is not OS quality, but that cosmetic stuff doesn't make any difference how they run if they're set up correctly.


Most are good, but some I have, had  soft or brittle parts.  The metal is not as good as an OS.  The quality goes a little deeper than the finish.  Unlike others such as Enya, Fox,. a few Rossi models, and many gas models that have little finish work, some with an industrial look, but are actually made well. 



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