maral

So, this is a fairly new Magnum .61 4-stroke that
has had about a gallon of fuel run through it.
The problem has developed where I was getting a pretty good full throttle rpm of 9-9.1k but the
idle was lousy which initially I attributed to it being new. So after about a gallon I still could not get a good reliable idle. Engine would die once the glow ignitor was removed. So I leaned out the idle adjustment and I can now get a decent idle but the top end has really gone out of whack where it appears to be running extremely rough and rich even with the high speed needle turned out only about 1 turn. Turning the needle out furter makes it running extremely rich and closing it any further makes it start to run too lean. It does not appear that I can get the top end to run up where I had it prior to messing with the idle needle. So I guess my question is have I gone too lean on the low speed which is now affecting the top end? Basically, I'm not exactly sure where to go with this engine. According to the magnum directions the factory setting on the low speed is 2 turns out, but the Magnun rep said that was about a turn too far so I adjusted it and things seem to have gotten worse. Any help would be appreciated.

mark

ajvpb

My Feedback: (3)

I have a magnum .91. The engine runs much different when cold than when warm. It will idle a bunch better once it has run. So, open up the low end back to 2 turns out. Open the high end to 2.5 turns. Start it, and bring it up to 1/2 throttle. Take off the glow ignitor, and it should keep running, but bog down. If it stalls, get a new plug. Anyways, run it up to full, and cycle between rich and lean for a minute or two, like you were breaking it in. Now very slowly bring the throttle back, to where it will keep running, but will knock a little bit (the knocking is it loading up with fuel). Close in the low end until the knocking stops, then lower the idle some more. Continue with this process until you get a respectable idle. Once you get it to a good idle, check the transition. Just make sure it doesn't die when you rev up. For me, the best idle I get seems to be ever so slightly on the rich side for transition, but its so small that I have full confidence when going from idle to WOT. Better to rich than to lean. Let me know how it turns out.

deputydog

I never could get my 61 to run right. Ended up giving it away to a friend who had one that ran great! He couldnt get it runnung either. I'm really good with engines but not this one. What I have seen is 1 out of every 3 or 4 magnums of the same type suck from the factory. Magnums are like the old Fox motor. Break em in slow and with castor. 1 lean run and you are done!

w8ye

My Feedback: (16)

I've got a couple of them. One wanted to run as you described. I changed to a OS 'F' plug and all was forgiven. Sometime later as the weather was warmer, I put the original plug back in and it ran fine.

Enjoy,

Jim

maral

Thanks. I'm actually running the OS F plug and still nada. I checked the valve clearance again and it is right where .1mm is a snug fit a TDC. Idle is good up to the point of about 1/2 throttle or so where I believe the high speed needle takes over and that is when things get ugly. It just runs really rough from that point to WOT. I don't believe it is fuel tank related as the tank is position just so the carb is slightly higher than where the fuel lines exit the tank. I've played with the low speed by going back to the original mfg. settings of about 2 turns out down to about 1.5 turns out. High speed started at 2 turns out down to about 1.5 to 1.25 turns out with no real improvement in the way it runs. One thing that I noticed after I got into the breakin which actually went pretty well and I have say the engine at WOT ran great up until a few runs ago but the high speed needle was not pointy at the tip but blunt.

Anyways, while it was previously running good a WOT the idle sucked. Now I've got a decent idle but WOT is as described above.

Mark

Gizmo-RCU

My Feedback: (27)

You are at the point where Magnum fs engines need to be re tuned as they are broken in. Just did that with one of my 91's yesterday. They are usually a little fat on the bottom end after they break in. The 91 was real critical on the bottom so go slowly and idle about 15 secs. before advancing the throttle, I have two other Mag fs engines and they behaved the same, good luck.

NM2K

My Feedback: (14)

Sometimes things do not go as planned at the factory. A new person on a machine may make quite of few parts that are not quite up to snuff, before finding out how to do it right. What if one of those parts is in your engine?

Rather than pull my hair out over something that I have no control over, I put the engine back in the box and send it back to those that warrant them. Problem solved, in most cases.

Keep in mind that every manufacturer makes a turkey now and then. It is just part of the human experience.

I own Enya, OS, Fox, Magnum, YS, BME, Zenoah, US Engines, Merco, Moki, MVVS, Webra, MECOA, LEO, Super Tigre, HB, HP, K&B, ASP, Quadra, Thunder Tiger and other brands of engines. The Magnums would not be in my collection if they were not functional. I don't collect wall flowers.

Patience, my friend.

maral

You may be right. I have a 91 that runs flawlessly so perhaps this one just needs some factory attention. Better to send it in than lose the plane.

mark

flapbreaker

My Feedback: (1)

If you have problems at anything over 1/2 throttle make sure that the tank is not too far forward and slightly crimping the fuel or vent line. This happened to me and my Saito would not even run over 1/2 idle. I just pulled that tank back and like magic it ran fine. Just a tip.

maral

Thanks flapbreaker. The tank neck mounts through the firewall and it appears they are not bent. At first I thought it was my fuel filler that may have been leaking air, but I eliminated that and I'm running the fuel line directly to the carb. I don't see any air bubbles in the line when I run WOT, but I'll give it one more look tomorrow and make sure that it isn't related to the tank or fuel lines.

Mark

flapbreaker

My Feedback: (1)

Mark, sounds like the fuel lines are probably ok. I had a wierd scenerio in my P-47. THere is a "tab" on the front of the wing and when I would put the wing on it woud push on the tank and cause the kinking but without the wing everything looked ok. Don't know what type of plane you have but like you stated if the neck is through the firewall hole then it shouldn't be kinked. Not sure what else it could be. I would try removing the needle valve and then fill the tank up until it flushes out where the valve was just to make sure there isn't crap in there somewhere.

maral

Update.

Well, I ended up doing a few things although I'm not entirely sure what may have fixed the problem. I ended up taking the carb apart and cleaning it. I also readjusted the valves, rechecked my low and high speed needles, went back to using the original high speed needle with the blunt tip and lo and behold the engine runs perfectly. It has a reliable idle at around 2.7k and I've got the WOT at around 9.1k. It has a nice transition as well. So, perhaps it was just a dirty carb, but all is well now. Thanks to all the suggestions.

Mark