acerc

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

My Feedback: (42)

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

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

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

P-40 DRIVER

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

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! 

Thanks again!
David

freakingfast

My Feedback: (3)

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

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

My Feedback: (102)

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

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

KW_Counter

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

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

flycatch

My Feedback: (26)

Most if not all Magnum engines are boat anchors. They are nothing more than a cheap copy of an OS engine.

rgburrill

Why go there? Magnum engines are NOT cheap copies - they are exact copies of the design with lower cost parts and labor. OS is like Toyota - too damn proud of their products. And a great many people using OS engines use Magnum spare parts, especially on the four strokes.

airraptor

My Feedback: (66)

So if it is a copy then you are saying OS is a boat anchor also.

there is always one guy that has turn a good thread into a pissing match. your statement would be sorta ok if in a thread asking if magnum engines are good but it isnt.

Cub Flyer Fresno

]

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

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).
Ilanded some 30% nitro fuel for cheap, and the 52 LOVES it !!

Cub Flyer Fresno

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

My Feedback: (1)

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

Bruce

RCPAUL

My Feedback: (1)

Thanks flycatch

You have made a significant contribution - NOT!

P-40 DRIVER

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

My Feedback: (3)

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

Ernie Misner

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

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

heavydriver

My Feedback: (1)

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