Moki 400
 

Hello,
My friend and me both have a moki 400 on a Airworld yak11 Reno racer versions 2.8m wingspan.
To be able to dive and race these small airframes for a moki 400 without harming the engine with high revs, I asked Fiala to make me a light prop for running in on the ground and a heavy loading prop for speed flying.
They made me a 36x18 2blade classic prop for running in, and indeed the engine swings this prop without effort. I ran about 4 liter of Aspen richened to 2,5% with this prop.
For flying they made us 36x18 4blade scale props with square tips. Today I tried one of these props and the engine only revs 2650rpm full throttle with this heavy prop!
Does the engine need more running in with the light prop? Will the prop unleash in the air because off the little slippery airframe? Or did Fiala miscalculate and is the prop just to big for this engine?

If a 36X18 was great, I fail to see how one would expect to add two more of the same size prop/pitch and expect good results.
Since you already paid for the prop, trimming an inch off each blade (and re-balancing) would get you to a 34X18 and probably would get you to a more respectable rmp's of 3600-3900 rpm's on the ground. I doubt if the plane would fly safely at 2650 rpms plus the engine would probably overhead due to overloading it.
My P-47 with a moki 250 turns a 4-blade 30X16 at around 3900 rpm's.

36x18 2 blade was not great, he spins it +5000 RPM on the ground and defenetly would overrev when used in flight.
It is a good prop to do some running in on the ground.
I do share your thoughts about the low RPM and maybe trimming the props.

Johan

Today I did some trimming to the 4 blades, I noticed the are 36x20! and not 36x18.
I cutted small pieces at the time and every time tried it on the engine, I finally got a 31,5x20 spinning @ 3200 to 3300 RPM.
I know this is still on the very low side, but the engine accelerates good and sounds great.
Will give it a try to maiden this way.

Everything seems in balance

Great Yak! Is it possible to get some info and foto of Your build? i sendt you a PM

Geir

Hello everybody, last week I recived my new Moki 300! Is my second Moki, I've been flying a 100 B Vt boxer for the last 4 years.
Today I break it in, and there is something is going wrong, it started ok, but when I pulled the throtle more than 1/3 the engine stops, and it don't start again with out choked again, althought it was warm. Do I have to open the needle H? It seems that is no gas...when it stops I can't start it again without open the choke...
The ignition batery is a lipo Rx 3000mah, 2S 9amps max dchg. The propeller a SEP 34/18, and I use Valvoline Syn Power 2T oil at 40:1.
There is one thing it makes me unconfortable, the ignition unite is not the red one with the 300 write in it, mine is a blue-grey one, with the 400 write in it. Are all the ignitions the same or there is diferent ignitions to the diferent engines cc..?
Thanks a lot and congratulations Scoot for starting this thread!
(Sorry for my poor english...!)

Jordi

Here are some pictures
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Not sure about the different iginition boxes with different size motors. But is sounds like the low end needle needs to be turns out to richen the mix on the low end. I had the same issue with my Moki 250. until I richen the low end mix and raised the idle position on the throttle. It now idles at 750 to 800 and transitions perfectly to a high RPM on ground of 3450.

Cheers

Thanks for your response GeorgiaF, you mean that if I open the L needle it will go everything ok? Don't have to open the H needle...?
thank you!!

Jordi

You may have to adjust the high end needle after you get the low end set. Another way to make sure you have the needles in the right area, especially if you have been adjusting them a lot, is to close them back down and turn them out to factory defaults. Low end about 1 and 1/8 turn out, Highend about 1 and 1/4 turns out. From the default points start your adjustments. you should not have to adjust more than 1/4 from the default. definitely no more than 1/2 turn from default. hope this helps.

Cheers

Thank you very much! on Saturday I'll try! I will coment the results!

Jordi

I've always run my Moki's at the factory settings with out issues. The Low end needle is set at 1 1/4 and High end needle is set at 1 1/2 to 1 3/8 turns out.

I figure if they don't run at there recommended settings then there is something else wrong. I have well over 100 flights on this motor and airframe and have never touched the needle since it came out of the box.

Hello Greg, I just did what you said with my Moki 100 B VT, just out of the box and flying four years like a swiss watch.

Tomorow I will check haw are the needles I'll put them on factory setings and I hope it will run ok!

Thanks!
Jordi

Hello! I just open a 1/8 anb the engine can rich 4000 rpm eith a 34/18 SEP propelller!
Thenks for all your help!

Jordi

Jordi,

Thats Great!!!!!!

Yes Greg!!!
I will feed it in a Top Flite Corsair, I have enlarget the plans to 120" .

Jordi

I'm a little lost in setting the needle H and L. The H I suppose I have to lean it until I rich 4000 a 4300 rpm . But, how can I set de L...? The transition of the throttle is quite slow... I had a lock at the spark plugs and they are very blach, this it meens that I have to lean the needles? Both or wich one..?

Thank you!

Jordi

I’m not certain about S300 specs, but 4,000 to 4,300 RPM on the ground seems high. I would be concerned excessive RPM on a new engine.

Also, can you fix the link to the pictures so we can see your pics?

Cheers

I’m not certain about S300 specs, but 4,000 to 4,300 RPM on the ground seems high. I would be concerned excessive RPM on a new engine.

Also, can you fix the link to the pictures so we can see your pics?

Cheers

Hello Mark, I'll reduce a little the max rpm 😄

Here you can see the spark plugs, there is a lot off black oil out from the exaust.

Jordi

Jordi,

My plugs look just like that also.

As far as the 4000 RPM on a 2 blade prop that sounds just about right to me. My 250's both ran at about 4100 on a SEP 32X18 break-in prop so i only flew it a few times on that prop and didn't push it to hard.
It was only when i changed over to the 4 blade on my P-47 and the 3 blade on my Wildcat that i saw the RPM's drop to the 3650 RPM's that they run at now. and i have not touched the needles in 4 yrs since i first ran the two motors out of the box.

I have 2 of the Moki 250's and they have both been treated and run in the same way with out any issues at all. From what i have learned about these motors is the needles on the carburetor are not what you use too change the RPM range
Its how much pitch you run in your props that will change that.

Greg,
Do you use an auxiliary fuel pump or a Turbulator?

Hi Richard,

Yes i do use a fuel pump, it just gives me better fuel delivery to the carb is all i'm using it for.