xe2

[] Beginners got an engine problem. Magnum xl ran great until a couple of hard landings that broke props. Recently I noticed a gray metal like substance mixed in with the engine oil that accumulates on the wing and stabilizer. The engine now stumbles on transition from low to high speed. It's also stalled twice in flight during transitioning from quarter throttle to full. Have the abrupt prop breaking landings that stopped the engine caused this problem? Is that gray stuff mixed with the oil a sign of internal engine damage. If so what are the typical components that fail and need replacement?

Anyone else ever had this problem?

loughbd

One probable casue is you pushed the crankshaft back and the crankpin is rubbing on the backplate. If so just push a rod into the gas passage and tap it back with a hammer. You may have also bent the crankshaft. Inexpensive engines bend easy.

asmund

take off the backplate and check if the crank rubs the backplate.

j.duncker

My Feedback: (2)

Also remove carb and look at the crankshaft. A piece of grit may be embedded in the crankcase and grinding away the shaft.

jamesg25

Ive had this happen to one of my ASP engines (ASP=Magnum) and believe me... it all ended in tears..
the diagnoses of the cause was one to many lean runs... being a real power freak, i had the think leaned out to the max, and i think it was the intense heat and a combination of a crash that finished it off. pull out the bearing and replace them, what has probably happened is that you ran the engine too lean, made the metal softer than it should be, then when you crashed the shock has dislodged something. if its anything like mine, you'll change the bearings, then notice a drastic decrease in performance, and thats when you give up and banish it to the trainer..

NM2K

My Feedback: (14)

It sounds as though the crankshaft is bent and it is egging out the connecting rod's lower end, which will also damage the upper end with enough running. When the connecting rod is really worn out, the engine will have to run very rich just to stay running. Glow plug life will drop to under ten flights due to contamination on the element.

If you or the owner are up to disassembling the engine, removing the crank and using a wooden or rubber mallet on a flat surface to straighten it back out and installing a new connecting rod should take care of it.

Otherwise pack it up and send it back to Magnum for repair. It should still be cheaper than a new engine. These engines will run a long time without problems if not abused.

No engine will take bopping its crankshaft very hard, but the cheaper engines are a little more prone to bending than some of the expensive engines.

red_guy

nope. can't be the crankshaft. I own magnums and I can tell you they are extremly tough. crashed one plane into the asphalt runway (felt straight into the shaft, well forgot to balance it , it was extremly tail heavy and could not land the darn thing) and the engine runs without any problem.

loughbd

You can bend the crankshaft on any engine. The Magnum is inexpensive and the shafts will bend easier than other engines. I have a box of crankshfts left over from my engine repair days all with bends in them. Many are OS 40 and 45 shafts which were higher quality that magnum. I used to take them to San Diego States physics department and have them straightened and use them for replacement parts.

The odds of XE2 having a bent shaft is high

Flyboy Dave

My Feedback: (21)

Take the muffler apart and see if the baffle is loose inside. This will show as
metal in the exhaust residue.

FBD.

Cyberwolf

My Feedback: (4)

Unless you have a lathe and a dial indicator its not advisable to be beating on the crankshaft with any kind of a hammer in hope that you might get lucky and accidently straighten it. .002 or less is very hard to see with the naked eye in a situation like this.

Flyboy Dave

My Feedback: (21)

With the right tools, a slightly bent crankshaft can easily be straightened.

FBD.

loughbd

Yup and the right tools are a lathe and dial indicator just like he said.

NM2K

My Feedback: (14)

If the crankshaft is bent, it is garbage.

You do not need all of the fancy stuff to "eyeball" a crankshaft. Just look for daylight between it and the top of a flat surface.

Flyboy Dave

My Feedback: (21)

ED....they can be straightened. I get them down to .0002 and less.
But then, I have been trueing and straightening them for 36 years.
These little one piece aero-motor cranks are childs play.

....and, with a brass hammer.

FBD.

NM2K

My Feedback: (14)

Yes, they can be straightened. That is what I was saying.

You can get them "straight enough" using a rubber or wood mallet on a flat surface. I've done it many times before. The Chinese crankshafts are generally very malleable, which is what caused the problem in the first place.

loughbd

Oh No Ed,

Haven't you been reading the forums?? The Chinese engines are sooooo much better than the japanese engines. How could they possibly have softer crankshafts?

mentorman

My Feedback: (2)

Look into and around the exhaust port on the motor to see is you see metal flakes there. If not then check the muffler like said earlier, it could very well be a loose baffle or where the two muffler halves come together.

Flyboy Dave

My Feedback: (21)

You can't really use a lathe and a dial indicator to measure the runout
(bend) of a crankshaft.

This is where "theory" (I think it might work) is different from reality
(the way it's really done) in the practical world.

This is also where the Guys that fiddle with the simple aero-model engines
in their garage, fall short of the Pro's who build/true crankshafts (all kinds) for
a living.

Building a crankshaft, and trueing it properly....is a lot more than putting it
on a flat surface....and whacking it with a hammer. [X(]

FBD.

loughbd

Yes you can and I have. I also used to take dozens of them to the Physics department at San Diego State and their machinst would straighten them for me. Iused them to repair engines for customers with bent shafts. They did an excellent job and the run out was less than .001 inch, more than within tolerances

loughbd

One more little item. When something is classified as thoery it is accepted as fact. You may mean hypothesis.

Flyboy Dave

My Feedback: (21)

Here is the reason why a lathe is not used as a crankshaft truing stand. Look
at this typical aero-model crankshaft....and think about this:

Say you chucked the small end....just past the threads into the headstock of
the lathe....and put the flywheel end into a centering tail stock. What happens ?

The part you want to measure is now running true....in the head stock. You
can't measure the out of round, cause it's running true in the lathe.

Lets turn it around and try it the other way around. Lets clamp the big
flywheel end in the headstock and put the centering tail stock into the front
of the crank....the bent end.

Guess what ? Same thing....the bent end is now running true in the tail stock.
This makes for inaccurate measuring. Some flywheels on crankshafts are simply
cast, not even turned....so the end in the head stock is wobbling as well.

FBD.

Flyboy Dave

My Feedback: (21)

This is the correct way to measure runout in a crankshaft. You rotate the crank
at the bearings, and measure at the ends.

Picture 1 shows a normal single cylinder, double flywheel in a real truing stand.
Picture 2 shows a three cylinder crankshaft in a truing stand. Here you have 6
flywheels pressed together on three crank pins, then the three separate cranks
are pressed together with all the bearings, seals, shims ect. to make the crankshaft
assembly. Then the assy is measured on the truing stand, and trued....

....with a big brass hammer. The whole assembly has to be within .001". This is
Journeyman work for sure....don't try this at home. I did this for 15 years, full
time....and was an Expert at it.

Picture 3 shows a technician tack welding the "big end pins" on a racing crank so
they will stay put at racing speeds. He has already trued the crank on the stand
to perfection.

Picture 4 shows my way of measuring crank run out. Simple and effective. No
special jigs needed....the crankcase is a perfect "truing stand".

FBD.

2slow2matter

My Feedback: (1)

I thought those were called counter-balances, not flywheels. My definition of a flywheel is a large, weighted ring on the outside of the engine that helps add inertia to the engine--keeping it running between strokes, and (in the case of cars and so on) creating a point of connection for the rest of the drivetrain.

Of course, I've been wrong before.

kahn41

My Feedback: (4)

Flyboy dave
BOY you hit the hammer right on the head! could'nt have said it any better. LISTEN ALL he is absolutly RIGHT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1
Greg

loughbd

You don't put it in the tail stock. You leave it free and turn the shaft with a dial indicator against it. Tap the shaft with a hammer until you get the run out to a minumium. I have doen this dozens of times. The shaft is usually bent just forward of the front bearing and it's easy to straighen this way. You can tell me it won't work but I have done it many times and I had the Physics Department machinist at SDSU do it for me dozens of time. I am running a straightened shaft in a Saito 45 and an OS 45 FSR. Both have no discernible run out and both run as well as they ever did.