Hey guys, sorry if this has been hashed a thousand times, but I couldn't find my exact problem. I am having a transition issue, please help.

MDS .40
11-5 / 10-6 Master Airscrew The problem happens with either prop.
10% fuel - Synthetic/Castor
Hanger 9 Performance Glow Plug
A little over a gallon of fuel through it.

The engine will start usually with one flip. At idle the engine will run forever either super slow or a slightly higher idle. Pinch test at idle (which I have to hold for a couple of seconds) will increase the idle speed and then kill the engine. A straight transition to full throttle is quick. At full throttle the engine is very strong and will run indefinitely. A very quick pinch will gain 300 to 500 rpm.

Ok, now for the problem. It doesn’t matter if I am flying it or on the ground, if I go to half throttle for a couple of seconds then increase to full the engine almost starts to 4 stroke. If I do a pinch test at that time, it will increase and run no problem. If I run at half throttle, then back off to idle for a second or two then go to full, no problem. But, I can not go to half, then to full; the engine will almost die.

Any ideas? Please help.

mb

try a different glow plug brand. my inverted .78 was doin that, until I put in an idle bar fox plug. That really changed the needle setup, and it was way rich after that. hope this helps ya fellow texan
d

bignasdy, thanks for the reply. I have a kb plug that has a idle bar and I will give that try next. If not, I will look into getting a Fox.

Anybody else have a suggestion?

mb

Hello!
well to me it sounds as if you have to set the idleneedle a little leaner!
The pinch test is not that precise...I'm not using it and no one I know off in pylonracing uses it.....much better is to listen to the engine and respond to it ....this takes a little practise but is really easy!
If the engine ,when you give full power from idle (you could wait 10 sec or some minutes ) sputters, hessitates and belching raw fuel out the silencer.....then the idle needle is set too rich ...and you better screw it in some. How much you turn it in you have to deside yourself but experience will give you knowledge, try half a turn!
Then do the same thing again: idle the engine for half a minute and then give full power, the engine should react at once without hessitating.
As for idlebar plugs ! They are a thing of the past ! Use a good sport plug as a Enya 3 ,OS 8 or a Rossi 3-4.
Fuel 5%-19% nitro .

If I read your post correctly, the idle is OK and it "loads up" at high and mid throttle.
sounds rich on the main needle. I say this as you state that going from mid to LOW throttle and then to high clears the trouble-doesn't sound like the low adjustment is loading it up (of course I could be wrong!)...I'd try an OS#8 or Enya#3 plug too.

Try a colder plug (if the engine permits that).

With a colder plug you will have to run the engine leaner to make it run right and that might solve your problems.

I always try to go for the coldest plug I can without endangering the idle performance. If idle suffers from the cold plug, I add a few % of nitro to the fuel to clear that up.

The tank position relative to the carb can also cause this problem. If your tank is higher than the spray bar, you will often run rich in the mid-range. This is pretty common with inverted engines... Try lowering your tank position, if possible.

Great, I love all the help.

The first thing I did was lean out the low end (jaka) a quarter turn. After I started it up I think I had to richen the high end a little, but I am not sure. Anyway, I got it running very nice. Perfect smoke on the high end, pinch test was perfect, and it wouldn't load up in the middle. However, after a few minutes, I tried an idle to full and it died immediatly. I turned back the low end about the thickness of my little screw driver and gave her one flip and she started right up and ran great. She is still a little rich in the high end, and dosn't make that middle to high transition perfectly, but it is much better.

I will keep reading your remarks, because it is probably a combo of problems. I think I will try my other plug today and see how that does. If I remember correctly the plug I have in it is pretty hot, so maybe dropping to cooler plug may help.

Again, thanks for all the replies, it is so nice to have such a great knowledge base to work from.

mb

I have the exact same problem with my OS .46 FX, a colder plug made it worse, tried a different fuel, different muffler,even different props, replaced all lines including the klunk,(yes I reset my high and low mixtures with every change, any leaner on low end resulted in too lean). This was all last season. Put a new piston and liner in it last week and broke it in on a 4x4 clamped to a sawhorse, ran great throughout the RPM range. When I screwed it to my Ultra Stick, my problem was back. The tank is centered with the spraybar. I've noticed that the engine seems to blur (visually) at the same rpm that it seems to load up at. I now suspect that the Dave Brown mount I'm using on the Ultra Stik is maybe too flexible and the excessive vibration at midrange is somehow affecting the mixture. The break-in mount had a sturdy aluminum mount, and it ran great there the day before. I'm going to try a different mount. I'll post the results.

JJ