George E.

My Feedback: (16)

My Magnum .91 2C mounted inverted in a pattern plane quits after running. Starts fine throttles up fine, idles fine but all of a sudden it quits. No sputtering just dies. Could be at half throttle or full throttle. Happens on the ground and in the air.

Funny thing is the engine worked great for about 8 flights then started this quitting problem.

Switched fuels Omega 15%, Power Master 15%.
Switched plugs same result.
Tried leaner, richer, same result.

This is a new problem for me. I really need some help here. Any ideas????[]

Flyboy Dave

My Feedback: (21)

Re-do your fuel tank and lines, and the problem may go away.
Check the muffler tap, and vent lines as well.

Dave.

George E.

My Feedback: (16)

I'll have to take the tank apart and look for a problem there first.

Funny thing is the engine may run at full throttle for 1 or 2 min then suddenly cut out like it was turned off with a switch.

rc-mike

Try another glow plug too. I had a 2 stroke heli engine do the same thing. It would run fine for a couple of minutes and then just quit without warning. The glow plug looked like it burned fine but I changed it and it went away.

George E.

My Feedback: (16)

I wish that was the problem but I've tried 3 different plugs.

Thanks anyway

rc-mike

Oooppsss, missed the switched plugs part.

William Robison

My Feedback: (3)

George:

Since you seem to have eliminated everything else, I'll speculate about a small bit of plastic in the tank, after the fuel sloshes a bit this little bit of plastic, which is too large to go through the clunk, gets pulled against the hole and shuts the fuel off.

Since this speculative piece of plastic trash is a remaining bit from molding the tank it's the same color as the tank, and you can't see it inside. When you refuel you blow it out of the clunk and all is well until it works its way back.

So if you have one handy, just replace the tank entirely and see if the problem goes away.

Bill.

Flyboy Dave

My Feedback: (21)

My trusty Super Kaos started dying out for no reason last week. The last
time it did that it spit the liner out. I changed the plug twice, and it sill died
out even at full thriottle for no reason. Starts right back up too. I haven't
had a chance to look at the tank yet, but it's been fine for 8 years or so.

Dave.

William Robison

My Feedback: (3)

Dave:

The engine in question here is a Magnum. Chromed liner, not nickel.

Bill.

Flyboy Dave

My Feedback: (21)

Uh huh....

....I was referring to the possible fuel problem.

William Robison

My Feedback: (3)

Dave:

Sorry, I looked at "...spit the liner out." and ignored "...look at the tank..."

Bill.

George E.

My Feedback: (16)

I'll try changing the whole tank and lines. I have a spare.

The Magnums usually are pretty good to me so lets hope it's the tank.


Thanks.

wep

A guy in our club had a similar problem. Turns out it was his bearings had just enough play to cause the engine to quite.

George E.

My Feedback: (16)

I checked the tank and lines and couldn't find anything but I have not tried the engine since.

I was thinking the front bearings could be allowing air to get by but that would also cause the engine to idle even when the throttle barrel was closed right?? Did the guy at your club have a hard time shutting down the engine???

jaka

Hi!
If an engine just suddenly stops abrupt... at idle or at any other setting it it most like the nitro content is to high!
Try 5% nitro and see what happens.
Regards!
Jan K
Sweden

Sport_Pilot

Jaka,
Magnums are set up to run on 20% or more nitro. They don't idle very well on 5%. Don't know about the equivalent ASPS over there, they may have a higher compression ratio which means they would run better on low nitro fuel.

Matt Kirsch

My Feedback: (21)

Leaking front bearings are a myth. If enough air to keep the engine running was leaking in around the front bearing, the front bearing wouldn't last long because it wouldn't be getting any oil.

On Magnums, the leak is almost always around the needles. User "Montague" suggested an easy fix that's been working for me on all my Magnums so far:

Shove a piece of fuel tubing over the entire low speed needle assembly, letting it extend off the end to seal the gap between the needle and the seat. Put heat-shrink tubing over the high-speed needle. On all the Magnums I've done this to so far, it's worked wonders. You can lean out the main needle, and they shut off like lights when you close the carb.

Sport_Pilot

Not that much air needs to get past the front bearings. Not much oil is needed to lubricate them. Oil can get through to the bearings and oil can still get to the bottom of bearing as air is leaking around the rest of it.

George E.

My Feedback: (16)

All good suggtions but I think I may be gaining on the problem.

I tried again after the new lines and tank clean out and had the same results. I think the inverted engine is siphoning too much fuel and when enough raw fuel gets on the plug, bam, quits. I didn't have the problem before because I thought I was too lean and have been richening up the high end.

How does that sound??????

Going outside to try a leaner setting now.

I may try the fuel tubing idea too. Thanks.

George E.

My Feedback: (16)

Looks like leaner was the fix [sm=thumbup.gif]

I was running about 400rpm below max because the engine is fairly new. I leaned it out to 300rpm below max and it quit once, 3 clicks leaner and I can't get it to quit on the ground, hopefully in the air too

I guess I was correct [sm=confused.gif] I was a little too rich and the inverted engine's plug cooled when too much raw fuel built up on the plug??????

Time will tell.

Thanks for all the ideas.