ernbar

I posted before about my problem, and would like to revisit the subject. I purchased my Magnum 120 back in 1997 for a 1/4 scale Cub. I could never get a reliable low idle. Yes, I've tried a multitude of plugs and different settings. Unlike my Saito that can spin that prop to almost a crawl. The motor was not used for at least 3 years, when I retarted it, it ran very rough at low idle. It then began to run backwards for very short runs and quit. After 3 weeks of playing around with settings, adjustments etc., I sent it to a friend who's good at fixing rc motors. He too can't figure out why it keeps starting backwards and then quits. He will go inside to check the timing and camshaft condition this weekend. Now for the weird part. He just bought a brand new Magnum 52 four stroke and it too is starting backbards and quiting. He said that it ran in the correct orientation the first time he started it a couple of weeks ago, but now it just runs backwards in a short burst and quits. He was questioning the "quality" of the Chinese made motors and I tend to agree. Has anyone had this same problem with a Magnum motor?

Don41

Here we go,,, I know I'll catch it for this comment but here goes. If someone offers you a Magnum engine (at any price) turn and run for all you're worth (:-).

Last year my pinch penny brother ordered the Magnum 52 and when it arrived it had absolutely no compression. The factory replaced it but we (long time experience) have yet to get the engine to run smoothly at lower speeds. The engine just seems to have its own opinions as to when and how it will run. It was like this on the test bench as well but we figured that it would eventually settle down.

On the other hand,,, all of the Saitos and OS engines, 2 and 4 strokes, run smoothly and reliably. I had the Senior Telemaster out last Monday, equipped with a Saito 82, and even though it has been parked for months it sat on the line slowly putting while waiting takeoff.

By contrast,, the bad boy Magnum, repeatedly decided to simply quit while still on the bench warming up. When he taxied out the first time it backfired and spun the prop. I will say, however, that once it got airborne the tempermental beast gave a good accounting of itself on latter flights. On one flight it stopped after landing but for the most part it was okay. Of course neither of us are fond of the long retrieval walk (:-).

Regards

JPMacG

My Feedback: (2)

I agree. Magnum seemed to have a quality control issue with their 2-strokes several years ago. They may have overcome it now, I don't know. If you are buying a used Magnum 2-stroke there is a chance it was a lemon. I would like to sell my hardly used XLS46A that I could never get to run consistently but I would feel I was screwing the buyer.

TexasAirBoss

My Feedback: (22)

The materials used in these engines were selected to be less expensive than the other brands, not better wearing.

chashint

I am heavily invested in Magnum four strokes and I like them.
I mostly have 91's , but there are also a couple of 70's, and a 61.
My experience has been golden, every one of them runs great, idles forever, and they have the same power as my OS 91's and 70's.
To date I have never even taken the valve cover off of any of them and won't until there is a reason to.
I have had one problem with a 91, the crankshaft pin broke during flight, I sent it to Hobby Services and they fixed it under warranty and sent it back to me, it took about three weeks total to get it fixed.
I don't know what the deal is about the engines running backwards, I use an electric starter and have no problems whatsoever with this.
As far as compression goes none of my engines feel like they have a lot of compression, but the 91's turn an APC 14x6 @ 9700, the 70's turn a 13x6 at 10200, and the 61 turns a 12x6 @ 10k on 15% fuel. These RPMs are ready to fly RPM not peak RPM.
Do I like the OS engines better ???
Yes I do.
But there have been a couple of times where the Magnums were on sale and Tower had the 25 off 150 code and that made the 91's 145 to the door. I guess you could say that I stocked up on them and I couldn't be happier unless I had bought even more of them.
Sorry you guys are having problems, if you ever decide to just throw them out I would be very happy if they landed here with me.

ernbar

I have used the starter and still runs backwards and quits. I wonder if its worth repairing and the cost if it has a stripped gear in the timing wheel?

dbacque

My Feedback: (3)

Mileage varies. I'm running an old Magnum .65 two stroke and it's never missed a beat.

Are you hand propping it or have you tried a starter?

Dave

ernbar

I don't like using an electric starter but I gave up on hand starting it. It has allways been difficult to hand start it, taking 10-20 flips to get it going. On the other hand, my Saitos just turn over with a couple of hand flips.

TFF

How well does it run backwards? If it wont run forwards at all then I would think the cam is off time; probably assy wrong. If it is running and pops backwards you might be running too lean; easy enough to fatten it up. Magnums dont hand start well for me and I have never liked starting 4 strokes by hand anyway. I would guess it is lean for one reason or another.

ernbar

It was set on the rich side, but I'm leaning on the timing issue. I think my friend is going to tear down the engine this weekend and that should give him an answer. TFF, it originally ran the correct orientation for a long time and now is when its acting up. I have never in 20 years of RC had so much problem with an engine[sm=48_48.gif]

whatwind

My Feedback: (1)

The only magum I have had trouble with is the 52 two stroke. What brand fuel? what %? the four stroke 120 like a couple of tanks of fuel sitting up right on the bench befour you invert them . nlyon prop on break in . you can almost count the revs at idle.

ZoomZoom-RCU

http://www.rcuniverse.com/forum/m_7648314/tm.htm

Click above to see some of my trauma regarding Magnums. [:-] The only solution....buy an
OS. I got the 56-fsa, and never had the first problem. My magnum did everything you described and more, and after wasting weeks of my life (and others) with no progress, I decided it wasn't worth my time. Yeah, you might get lucky, but I'd rather have reliable.

ZZ.

khelsea

I just ran into a problem with my 52 magnum over the weekend. Wouldn't start. Turned out the idle screw oring was not holding the idle jet so it was leaning, turning in while running. A change of oring cured the problem, now runs sweet, something to check Khelsea

ernbar

ZoomZoom-RCU

AHHHH! You know how I feel! Did you ever get back the engine repaired from Horizon and did they tell you what the problem was? My buddy was supposed to break the motor down this weekend. I've called him a couple of times but his not answering. I wonder if my Magnum engine got to him too! If he can't get anywhere with it, then its time for an OS. I just got another airplane ready for flight that I mothballed about 7 years ago and after spraying some Sea Foam inside to loosen the frozen parts of the OS 35 FP 2 cy, it cranked up on the first flip of the prop. Thank God for OS quality and reliability!

ernbar

A happy update, I think[sm=72_72.gif]. My buddy says that after several days of tinkering with the engine, it finally started in the correct direction! He was getting ready to tear it down but decided to try the starter one more time and finally cooperated. If you try to start it by hand, it runs backwards. As a matter of fact, it also ran backbards when a starter was used. Lets see how long this works, next time its the trash for the Chinese jem!

ZoomZoom-RCU

Nope, haven't heard back from Magnum yet. But once I do receive it back in what should be mint condition, I'm not even starting it.....its gonna be sold. Hope yours works a bit better now that you seem to have some positive results. Seems these Magnums are just not high enough quality to run from hand starting....if you read my thread thats one of my prerequisites.... so if your using an electric starter, you may be ok...barring of course other issues which there well may be. As for me.....I'm enjoying the simple reliable one to two flip start up of the OS. 56a. Haven't had the first hiccup, and I'm through the breaking in period and into the third and fourth tank. There is simply no comparison.

Good Luck with yours!

ZZ.