I am having trouble with my magnum 108 2stoke. it runs well for about 3 tanks then it start to fail (running hot)
every flight I have to adjust in idle and high. but it keeps on failing. I had used it for about 4 gallons. (first 2 gal. ran ok, then.....) I am usin 15%nitro and a masterscrew 14x8.
I have tried 5% nitro and 13x9 blade. eventually same thing( 2 emergency landings, 1 crash) changed plugs, cleaned inside out.
Heeelp ! before I discard this engine into the trashcan.

Roro it sounds like you are running lean. My guess is that something on the engine is not sealed tight. I would suspect the back plate. The carb may also have come loose or slipped in the neck of the front housing. Check all the bolts and check the carb to be sure it is tight and sealed. Also double check the muffler. It may be partially blocked or loose. These are the things I would look at first.

Mark Shuman

thanks for the advice, I will look into this details.

I had a similar issue with mine. I found a small air leak around the carb, double check the seal and alignment. Maybe the fuel line itself.

I just read your post (7/30/2004) I just got myself an 1.08 just like yours. Tell me, did the advise they gave you worked? If they did, how's your engine being performing since?

I have owned a Mag 1.08 for several years and it hasn't missed a beat. I did find it likes to be lugged down with larger props and did nothing when I tried to rev it up and put the smaller ones on it. My best props have been a 15-8 or a 16-6.

Since you have 4 gallons through it, I would check all the gaskets. They may be getting old and hard. The O-ring under the carb is a good place to start. When you replace it, rub a little high temp silicone gasket material on the base of the carb. I use the Permatex brand from Auto Zone.

By the way, I am using the front needle valve, not the remote.

All the magnum engine I've ever owned. I just Jb weld the carb to the
engine right off the bat and they all run like champs after that.
It seals it and prevents the carb from rotating loose.

You also want to flush out the needles. Sometime crud gets in there.
Check for loose screw on the head, backplate, ect.
Also try checking the line in the tank. There was a little nik or slit in the line one time.
It started picking up air as the fuel level got lower. It drove me nutz.
I was thinking the engine was crappy becuase it died or over heated after
I put the plane in the air.

For some strange reason I had to backout
the HIGH END (richen)
and lean the LOW end to get idle in.
You would think it's the other way around.
Also remember it's winter time now.
The air is cooler and densor, needs more fuel.

Like Ed my 1.08 ran great with a bigger prop. I used a 15x8 and 16x 6. These motors pull hard below 10K.

I have owned 3 Magnum's of various sizes and the 1st 2 had the same sort of initial running lean problem.
The 1st took a while to figure out but having learnt from that one when the next 1 did the same thing, I looked and found the same problem.
Basically their machining QC isn't consistant.
I found that there was excess machining"flash" on the carby barrel and that had scored the carby inner wall. allowing an excess of air to enter, irresepective of what position the throttle servo was in.
I stripped the carby on the 3rd engine BEFORE I started it for the 1st time and hey presto. Same thing!
A points file and a magnifying glass fixed the problem.
Once the flah was removed, I reassembled the carby and the engine ran beautifully once it was run in and tuned. I only run 5% Nitro fuel.
On the smaller Magnums (.46) a Tower Hobbies .46 or GMS.47 tuned muffler, in lieu of the stock Magnum muffler, really sparks them up.

I ran the engine again on sunday. It took a while to tune but still the transition is not as smooth as it should be. I am running 5% fuel,14x6 prop.
it turned at 9300rpm. Definitevley it ran way better than the last time it crashed on me. also found that the needle is a little bit loose, Do you think air could get in thru there? I think I will follow Ed-moon{s advice and seal the carb .
keep you posted.
thanks everyone.

adendum: Ed-moon{s should be Ed_Moorman.

Yeah sometimes the o ring on the needle will get flat or dry/crack allowing
air to seep in. A new O ring perhaps.

Check to see if it's just that little tab thing that's bent out a little that
dosen't give a tight or click field on the needle.

The next time you go out to the field, notice some people
have fuel tubbing over the needle to try to sholve this problem or prevent
the needle from rotating during flight.

You might try richening the highend a little at a time first.
With the nose pionted up, have a couple of guy hold the plane. I guess.
and check the transition.

Perhapes your engine is doing this ? Splutter as you're taking off.
It's from the oil build up in the muffler from idling which must be cleared out.
This why I give myself plenty room for take off.

Once the plane is in the air , It'll run fine if it's on full throttle or close to it.
The engine doen't over heat or die, if you choose to run a full tank.
But it transition like crap.
I leaned the low end a little bit at a time to dial her in.

If you can't get it to full throttle without the engine wanting to die.
The high end is too lean. Give it more fuel, but by doing so
you must retune the low end to give a better transition.

Thanks leftnut:
I will no more have trouble with my magnum 108.
as I was flying onsunday, everything was fine for the first 7 minutes, then, as turning into the downwind leg about 150 feet up my tiger went non responsive full throtle straight to hell ( well it tried, but it only made a hole in the ground about 5 inches) broke the carb, muffler , and have not the guts to find out more(still in a plastic bag). I have the feeling that the baterie unplugged in flight but is only that.. a sad feeling.
thank every one for their input.
have a nice 2005 and safe flying.