What does it mean when you have a motor idling pretty good and when you throttle it up to about 3/4 to almost full throttle the RPM will drop significantly and the motor will die unless the throttle is brought back?
Thanks!

Probably going lean at high speed.?

Enjoy,

Jim

And or the prop is to much and is killing the carburator suction.
Quick check-- put on the smallest RECOMENDED size prop. If the response is razor sharp, you know you need a smaller prop.
Another check for too big of a prop. Flip the plane vertical at WOT. It should not sag in RPM at all.-------Go to smaller prop.
I think propsizes are picked by a sales man at some companies.

Yeah sounds lean. Richen up the high end and see if it goes away. What prop is it?

I am running an 18x8 which is the smallest prop that the motor asks for. I was thinking it was lean but as I was richening it up I wasn't getting the full results I wanted. I will try to richen it up slowly. I just couldn't determine if I was too lean or rich. Any other suggestions?

Your fuel may be old?

If it is an older motor check to see if the ring is not gummed up. I had this problem with my Moki 180. its was a Great motor. if the ring is gummed up and not moving freely put i on a bit of emmery paper with some oil.

I am running brand new fuel 5%. How do I check to see if the ring is gummed up? Do I have to disassemble the motor? The piston seems to move very easily in the motor.

If the engine has compression, the ring is not gummed. Apparently it has compression, you got it started.

Yea I can actually get it to start on 1-3 flicks. It will Idle well but when I give it more than 1/2 throttle it begins to die. I guess it must be to lean. Any other suggestions?

If the idle circuit is gummed up or has a piece of lent in it. It could effect your high speed operation.

This one has the carb with the big disk on the side to set the idle mixture?

Make sure the marker on the disk is set at the neutral point.

Enjoy,

Jim

Yes this is the one with the big disk on the side to adjust the idle. I started adjusting that to get it to start and hold an idle. Where is the neutral point? When you say that if there is a piece of lent in the iddle circut do you mean the idle setting or the high speed idle valve?

There is a shaft attached this disc inside the carb. it has a little narrow slit in it. This slit can get a piece of trash in it.

There should be a dot or line on the side of the disk. This should be straight up for the usual setting

You cant guarante the ring is not gumed up without taking the piston out. You can guage the compression it has. it shoud be quite hard to flick over the compression. it will still runn even if the ring is gummed but you will get similar symptoms to a lean run. ie quits after running for a while and it will get hot

Here's a picture of what I was talking about.

Thanks I will check those things out. Any other suggestions?

Here's a link to the place where the picture came from...

http://www.justengines.unseen.org/moki_carb.htm

So the holes need to be lined up when the throttle is closed?

as w8ye said .. there coud be a fuel blockage somewhere, e.g. clunk fuel line or carby or an air leak . check al of this as well if you are in the mood

Parts explosion click on this link

http://www.justengines.unseen.org/moki_parts.htm

I have new fuel lines that I have checked for leaks. Do either of you suggest disassembling the high speed valve to clean it? What should I use to clean the carb?

I'm afraid its been about three years since I've seen a Moki or messed with one. We may need to wait for someone with recent experience?

Enjoy,

Jim

Right now, I would try to force some fuel through the fuel inlet with your fuel pump. Maybe that will get any junk if there is any out of the metering system?

This way you are not disassembling something you are not familiar with?

I have forced fuel through by blowing on the preasure line that attaches to the carb to make sure I was getting fuel through. It was getting through just fine. I must just have the high idle set to lean. Do you know how many turns out from closed one should start with?

Ye i Would be takinf the high end needle apart you will see srtraight away if its blocked gently scape any gum out of the bajo .. the part that the fuel line attatches to. just uses a piece of soof wood sharpend to a point. poke a piece of wire down the hole where the fule line attaches to to make shre its clear.