I have a magnum 70 four stroke on my phoenix models sukhoi. Both are brand new. The engine seems like it misses at the hi rpm setting. This is the first 4 stroke for me. i have been running 15 percent 2 stroke glow fuel. Is this the problem? I mounted the engine at a 45 down angle but have now since moved it to a horizontal mounting (used to that with the 2 strokes) Still have the same issues.

Your Magnum XL .52 RFS is a ringed four-stroke engine and will require considerable break-in before it will run reliably. The owner's manual should advise you to run the engine extremely rich, keeping it under 5000 rpms or so for the first ten minutes of run time. After that, you will want to continue running it very rich, leaning the needle slightly with every subsequent tank of fuel.

Your 15% nitro fuel is fine so long as it contains some castor oil as lubrication. Magnum doesn't recommend 100% synthetic lubrication for their engines. I'm more curious about what kind of glow plug you're running and what you've done so far to correctly break in the engine.

If you're not running an O.S. F-type plug, that would be the very first thing I'd recommend you try. More information about your plug and break-in proceedures will help us help you.

The Magnum 70 four stroke has a bit different carb in that the idle jet screws out to a stop vs in for all others that I've seen. Idle jet setup can affect the high end.

You need to break in the 70 a bit before flying it. The third tank is enough break for flying, but the engine will not be at it's peak for at least a gallon of fuel

The fuel I use in everything is Omega 15%. It has a castor mix and the Magnums manual recomends that the fuel have either full castor or a castor mix. It works so I don't worry about it. I do know that Cool Power 15% did not run well in my Magnum 90.

Set up both needle to the manual's starting point. If memory serves me, it's 2 1/2 turn from closed on the high speed and the idle one is two from full out. Start the engine and let it run a bit with the glow stick still on. It should be running ragged at this inital setting, ans smoking like crazy. Now go full throttle and slowly lean out the top end for max RPM then go back to the rich side by at least 500 rpm, 800 would be bettter. Now set the throttle to as slow as the enging will go and keep running. Don't worry about the speed at this point. Lean the idle very slowly for maximum RPM at this throttle setting. Now go back and do the high end again. Back on one more time on the idle side, this time the rpm's should be a lot slower that what you started with. When get this setup, adjust the throttle for 2400 rpm. Now, remove the glow igniter. Check out top and idle one more time.

Get the engine well warmmed up and run it up full throttle for a cound of 10 or so then go to full idle. Let it idle for a count of 30, it should putt putt along without any detnotation. Now jam the throttle full open. It should jump to full RPM without hesatation. If it stumbles and slowly gains RPM, the idle it to rich, lean it by 1/16 turn and try again until you can jam it and have it jump to life. If the engine just dies when you jam the throttle, the idle is to lean, back it out 1/16 turn at a time untl it jumps to life,

This should give you a good setup. My 70, cranking a 12-6 is good for almost 11,000 on top and will putt along at 2200 for a long time. It is mounted on it's side.

If you can get the engine running right with the above setup, you may have a fuel tank/line issue. Check for bubbles in the line, not good. Also make sure the tank centerline is level with the spray bar. If it is to high or to low, it can give you fits.

If all these things don't resolve the problem, I would pack it up and send it back to Hobby People for a check out. They are good people to work with and all it will cost you is the postage. Don't mess with valve lash, it is set right from the factory and if it is wrong, let Hobby People fix it.

Last, when you get the engine running right, don't mess with the needles until the engine starts runnig bad. We have a couple guys at the field whose every day ritual is to burn a tank of fuel screwing with the needles and they still end up dead stick. Get the set and the wait for the engine check lite to come on. You will probalbly reach this first point about 1/2 gallon into the break in. Maybe once more at the end of the first gallon. Then maybe once every case of fuel you will have to tweek the adjustments. After the firs couple gallons, you can experment with different fuels, by then you will know how your engine runs and can really tell what the different fuel is doing for or to you

Don

Okay i got the thing running and tried to fly it twice and both flamed out. didn't run it at full power long, just long enough to set the high speed and get into air, flamed out both times. then thats when i did what magnum said to do i ran a tank at half throttle, let cool, ran another tank at full, let cool, both on the rich side. I then tried to set the high speed by leaning and still getting a miss in the engine it seems, i am using a os f type plug. it does look gray and kind of carboned over now. batteries ran down about half way through trying to set the thing up on that third tank and plus we had to swap our spray plane over.

i am running the pink omega fuel with caster oil

Every engine I ever broke in, (three), needed a new glow plug before it would "air tune" properly.

What size prop are you running?

The only problem I`ve encountered with the Magnum 4c , is the LS needle would turn it`s self in when running . Causing it to run lean in flight.

i am running a 13x6 master airscrew prop

Are you using a tach to set the high end ?
If so what RPM are you getting after a about two minutes at wide open throttle ?
On this engine (even though it is not fully broken in) I would expect close to 10k sustained RPM with a MA 13x6 prop.
It should peak greater than 10k with the MA 13x6.
The Magnum engines I have do not really run well when they are set to rich, and sound like they are missing once in a while.
Unfortunately they will also sound like this if they are to lean.
If you don't have a tach I really recommend buying or borrowing one.
As was mentioned earlier I too have found that new engines are prone to eating a glow plug.

I don't have a tach but may look into getting one.
i replaced the glow plug and still having troubles. Oh well i may mess with it some more this week.