Idle while breaking in Magnum .70 4-Stroke
 

Hi guys, Well I have been following the instructions to a Tee on breaking in myMagnum .70 manualfound on this link:media.hobbypeople.net/manual/210945.pdf. I've got my 45 minutes of run time starting from very rich on the top end to just rich now. I've got it at about 2 turns out. Top RPM right now is 9750 but a bit jumpy due to the newness. Top end feels right so far and I'm not ready to max it out yet. The bottom end is another story. I can only get my idle down to 4500 or so before it just quits, no sputtering or coughing, itjust stops.This is hardly an "idle". The low speed needle is 4 turns IN from the OUTposition as the manual states. I have tried to open it and close it from this position both directions an 1/8 of a turn at a time (as written) but only straying about 1/4 turn away from 4 turns each way. I'm not sure right now what to do. It does seem to transition well from my 5000 to 9700rpms well. Does my high speed needle being rich still effect the Idle to 5000rpm range? What is a standard magnum, high end and low end needle valve turn position? I would assume 2 on the high end is a bit rich still. Do I need to adjust the low end a bunch more? If so which way? And then should I pull the cover and check my valve clearance? My fuel is the Sig 10% nitro 25% castor mix since the manual wanted at least 18% oil content for break-in.I've got roughly 1/4 of a gallon of fuel through this engine and it never has idled for more than a few seconds below4500rpm.It is sideways in a GP 40 Corsiar Kit. I think that's all the answers to the questions you might have! Thanks for the help!</p>

RE: Idle while breaking in Magnum .70 4-Stroke
 

the highend will affect the low end but it shouldnt be that bad. your idle is way to rich (it always is from the factory) try turning it in 1+ turns until you notics that your idle speed starts to drop. once it starts to level out let it idle for 15 seconds then gun it to full throttle, if it studers then goes your a little rich, if it stops then goes to full your a little lean, this can also happen if you are way to rich.

RE: Idle while breaking in Magnum .70 4-Stroke
 

What prop is on the engine?
What glow plug is in the engine?

There are no "standards" for needle settings. All you can do is start with the settings in the manual and adjust from there for your specific combination.

Some Magnums, especially if they are the "old style" with the open vent on the bottom of the case, will not idle until they've had about a gallon of fuel through them at wide open throttle.

RE: Idle while breaking in Magnum .70 4-Stroke
 

This magnum is brand new from hobbypeople.net and has the oil tube that returns to the engine. I am running an O.S. F glow plug. 13x6 prop as recommended by the manual for break-in. Hope this helps. I realize that there are no standard needle settings but most of the time they are within 1/2 or a full turn. if you ask most people.

RE: Idle while breaking in Magnum .70 4-Stroke
 

Maybe it's me, but I don't understand this-Your low should be turned out a couple from closed. I never trust the factory setting. I turn them both in till closed (checking thier setting) then open to the recommended to start off-you may wish to do it.

RE: Idle while breaking in Magnum .70 4-Stroke
 

Seems odd to me too frenchie but it says it right there. It has to be right! http://www.rcuniverse.com/forum/js/f...wink_smile.gif

RE: Idle while breaking in Magnum .70 4-Stroke
 

How do you know where out is? Is there a stop on out?

RE: Idle while breaking in Magnum .70 4-Stroke
 

I just checked one of my 70's and it was about 1 1/4 out from in. It runs great.

RE: Idle while breaking in Magnum .70 4-Stroke
 

Irish, Yep it actually stops on out. I was suprised myself. http://www.rcuniverse.com/forum/js/f...eeth_smile.gif Your setting sounds better to me so I will start turning it in and seeing what it gets me. Thanks for the help. I'll keep you posted.

RE: Idle while breaking in Magnum .70 4-Stroke
 

Well I got the issue pretty well figured out thanks to all your help. The low end is ending up closer to 5.5 turns in from the out position. I got the idle down to 2700rpm and think it can get more reliable with some tweaking. At least it's looking flyable now! Thanks all!

RE: Idle while breaking in Magnum .70 4-Stroke
 

I've never touched the low speed needle on any new engine prior to break-in. I set the high speed to whatever the recommended starting point is and go from there. I guess I've been lucky because all of my engines have started and run well enough to be tuned.

The OS-F and 13x6 is what I've used on my 70s. After more run time and fine tweaking you'll probably get around 2000 idle speed with no problems.

RE: Idle while breaking in Magnum .70 4-Stroke
 

Frenchie, that isn't good advise for the Mag 70, but with other carbs and you are correct. You have to start with both needles set to factory recomended settings and fine tune from there. Screwing in the idleis removing it. You start from a fully out setting and make the adjustments from there like the manual said. I about took a hammer to my Mag 70. Guys at the field were giveing me that same advise as yours and things just kept going down hill.

That carb is a real balancing act. If the Idle is off, you can tune the high speed but then the idle is still awful. Going to work on the idle ends up with both being off. Once you get it tuned in though, it is a great running engine. I flew mine over a couple years after getting it tuned the first time and I don't think I went over a click or two away from that first tuning the whole time. It's a rock solid engine.


Capt17, after a few more tanks, you should be able to get the idle down very close to 2000.

From where you are now, adjust the Highspeed for maximum rpm then go rich about 400 rpm from there. Set you throttle for as slow as the engine will go without stalling, and at that throttle setting start leaning the idle for maximum RPM. Don't touch the throtle. Once you have that, then go back to full throttle and adjust the top end again.. Go back to the idle and adjust it again. You will see quite a drop in idle speed now. I recomend a minimum of three times through this, then work the transistion. With the fresh engine, you should be around 2200 to 2300 max at idle and it should thump over for quite a while at that speed. Earlyer recomendations on transistion are good.

Don

RE: Idle while breaking in Magnum .70 4-Stroke
 

Thanks guys, It started snowing again and we have 6 inches on the ground with more comin. I guess fine tuning will have to wait a bit but at least I got to a workable idle speed right now. UPSguy did deliver my solartex today in the snow. That's always a good inside activity! http://www.rcuniverse.com/forum/js/f...sn/biggrin.gif

RE: Idle while breaking in Magnum .70 4-Stroke
 

I have the Magnum 91 and I have yet to start it.  I frantically dug out the manuel and read it comparing your postings.  Yep capn, I see exactly what you were reading.  My bet is the 70 and 91 are different in displacement only.  Not glad you are having a tough time of it, but glad you started this thread.  All the info I can get before starting mine is a big help.  Probably gonna be about 2 more weeks before I fire mine up.  Keep us posted on your progress.

RE: Idle while breaking in Magnum .70 4-Stroke
 

I have the .91 also. Itried to set the LS the way the manual said but it never stopped when turning it out, just came all the way out. Iscrewed it all the way in and then out 2 turns. I've got a gallon or so through it now and I haven't changed the LS yet. It idles and transitions well. 20 flights or so on it and no deadsticks or any other troubles yet. I love Magnum!

RE: Idle while breaking in Magnum .70 4-Stroke
 

My Magnum 52 has been a PITA since Ibought it. Iam still trying to get the low speed needle figured out and it probably has at least a gallon throught it.

RE: Idle while breaking in Magnum .70 4-Stroke
 

On the Mag 52, pull the idle screw out and see how tight the O Ring fits it. It shouldn't rattle around on it , but some do. If the engine is fairly new, Iwould contact Global hobby and send it to them for a look over. I fought my Mag 52 with bad idle for quite a while and then Global sent me a new carb. It ran really nice for about three tanks and then started acting up again. I sent the whole engine in and the did a complete turn and replaced some O rings again. While the engine was in for the last time, I found a near new OS 52 and jumped on it. I've really not had a chance to check out the Mag after it got back and thats been almost four years now.

One other thing I found out from this list was that while all Mag four stroks and some 2 strokes, use the same replacement highspeed needle valve, not all of them are the same from the factory. The 52 comes from the factory with a stubbyer taper than the big engines and the replacement needles have. The longer taper makes hitting the sweeet spot a little easier. If you have a Mag 2 stroke try swapping the high speed needle with it.

Last, if you arereally frustrated and Globalcan't help. you can always put a O.S 52/56A carb on the engineand all is good. It is abolt on replacement. The only isue you may have is if the engine was tucked tight to the motor mount, the O.S. carb may interfer with the mount. I ran across that and I just replaced the sockethead screw behindon the mount,with a flat head screw after counter sinking thehole.

The descrepency on the 70 and 90 instructionshave me wondering. I've gotmy older, Mag 70 as well asa NIB 70 from about two years back. I've also got a couple 90's, one well used and the other new ona plane. I'llcheck theidle screwson all four to see if there is any difference. Mag may have changed the carbs mid stream and not changed the manual. I'll let you know what I find tomorrow.

Don

RE: Idle while breaking in Magnum .70 4-Stroke
 

I started my 91 last night.  It ran very well.  It seemed to be running at a very good idle, but my tach battery was too low so I could not get any good readings at any speed.  Plus it was just to d#%^m cold to hang out in the garage with the door open and changing throttle settings in the prop wash.  It should be warmer tomorrow and I already replaced the tach batteries. 
Man it sure did sound great.  I love 4 strokes.