jdp8488

My Feedback: (11)

My MDS 78 has a very slow throttle response when converting from low/mid throttle to full. I have adjusted my needle valve several times, but no change in the response. The engine runs very well other than the throttle response. I hear these MDS engines need a very hot plug and a low nitro percentage in fuel. I am running 5% omega with stock plug. Could the plug be the problem? The reason I want a faster response is I have the engine in a Razzle 3D and when I am entering a hover, my engine will not rev up fast enough to hover, the plane will stall out before the engine is running fast enuogh rpm's to hover. Thanks for any info provided. Justin.

w8ye

My Feedback: (16)

What prop are you using? Do you have it over-propped?

Jim

Homebrewer

My Feedback: (8)

First of all, remove the stock plug. It is only good for several runs during break in and is a piece of junk.

Also, sounds like you are over propped. A 13x6 APC would probably be your best bet for this engine.

Andy

jdp8488

My Feedback: (11)

Actually, I am using a 13x5 zinger. So it couldn't be "over propped." I will purchase a new plug soon. Should I go with an idle bar or not? I will see if that changes the performance. Thanks for the info. Justin.

Texastbird

My student had the same problem with his 78. But with a #8 os plug and an APC 13x8 prop, this motor has become highly respectable. Remember though that the ring needs a long time to break in properly, and they don't run too strong until after a gallon or so of fuel.

jdp8488

My Feedback: (11)

One more 12oz tank through her and it will be a gallon. Although, the motor already runs very strong, its just that very laggy throttle. How fast does your students motor rev up. With the 13x5, my prop would spool up much quicker the the 13x8, yet it doesnt spool up quick at all. I just keep telling my self it is the plug, and until I buy a new, hotter plug, I will not know. Well, thanks for the info texastbird. Justin.

Texastbird

When we give it full throttle for takeoff it has as quick a response as any glow engine I have. I haven't even had to touch the low speed needle as of yet. Maybe just lucky on this engine. Just get the os # 8 plug as soon as possible and see if that doesn't solve all your problems!

jdp8488

My Feedback: (11)

I will pick one up tommorow and see how the engine performs. Thanks, Justin.

jdp8488

My Feedback: (11)

Well, the plug was not the only problem. When I put the os 8 plug on at the field and cranked up the engine, my motor was not idling very well. I went ahead and took off. About 30 seconds in to the flight, the engine cut off. The razzle floated right back down to the runway. I tried to adjust my needle valve and leaned the motor out a bit. Took off again, dead sticked her again. Then I got a few guys to help take a look at everything with the cowl off. We noticed some air bubbles moving through the line. When I got home I fitted some smaller diameter fuel line from the tank to the remote needle valve. Cranked her up and everything ran beautifully. Smooth idle, smooth transition from low throttle to high. I am very impressed with the MDS 78 so far. I have 10 acres so I went ahead and took off to try some torque rolling and hovers. The 78 had good power, but a little slow on pull out. Still, the 78 is a good engine for only $100 at my LHS.