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MOKI RADIAL Care and Maintenence

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Old 10-05-2018, 09:44 AM
  #4201  
Moebius44
 
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Originally Posted by Captainbob View Post
Two years ago I bought a Moki 250 for a comp arf F4-U i was building. Initial test running on a test stand was not satisfactory. it wasn't possible to get the high speed mixture rich enough (turn the needle out three or more turns no drop in rpm). I settled for this, finished the airplane and installed the engine and test flew. However, the Moki quit frequently, once in flight, and was just very temperamental. I started reading others comments in this forum and found out that many were having similar problems. At one point V.A. came out recommending an electric fuel pump. To me, this was an admission from the factory rep. that the engine had issues. Finally, out of total frustration, I discarded the factory Walbro carb. In it's place I used an O.S. Max 8B carb I had in my "junk box" (I believe O.S. used this on their 108 motor). GUESS WHAT! All problems disappeared. I use no pump of any kind, not even muffler pressure. The throttle response is much more linear and CH temps have dropped from somewhere around 250F to less than 200F (Jeti telemetry). I've had many flights on the Corsair since making this change and I no longer have any concerns about the engine stopping in flight or any other time.
Great idea; a quick check online appears this carb is not available. Is this so? Can you enlighten us about mods required? Now wondering whether they may be another, more readily available carb that would also fill the bill. I'm really after reliability on an aerobatic setup.

Thanks...
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Old 10-05-2018, 01:11 PM
  #4202  
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Yes, this carburetor is probably not available. But I,m sure that any nitro R/C two stroke carb of similar size will work. One that comes to mind is the Moki 180/210 engine carb, a very high quality unit by the way.
The main problem with the Walbro is that the carb throat is too large, this. causes a very weak DELTA P in the venturi. The throat area of the O.S. carb is 62 pct. of the Walbro.
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Old 10-05-2018, 01:17 PM
  #4203  
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Originally Posted by Captainbob View Post
Yes, this carburetor is probably not available. But I,m sure that any nitro R/C two stroke carb of similar size will work. One that comes to mind is the Moki 180/210 engine carb, a very high quality unit by the way.
The main problem with the Walbro is that the carb throat is too large, this. causes a very weak DELTA P in the venturi. The throat area of the O.S. carb is 62 pct. of the Walbro.
Thanks. I have a 215; I ownder if it has been established:
- if the two engines share the identical carb
- if either the 215 or 250 has demonstrated a greater difficulty to tune / keep running reliably.
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Old 10-05-2018, 06:05 PM
  #4204  
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Just read the posts.This forum topic goes back to 2009. And from the beginning a lot of the posts had to do with how to adjust the needle valves properly, how to prevent overheating, the necessity of keeping the impulse line free of grease, and so on. The only "fix" the factory could offer was the electric fuel pump which is expensive, must run all of the time, and probably is going to require an additional battery pack. And this "fix" doesn't really address the main problem. It is merely a substitute for the Walbro pump which is relatively trouble free and requires no electric power. Eliminate both these problems- get a two stroke nitro carb.
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Old 10-05-2018, 06:11 PM
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Hinckley Bill
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Originally Posted by Captainbob View Post
Yes, this carburetor is probably not available. But I,m sure that any nitro R/C two stroke carb of similar size will work. One that comes to mind is the Moki 180/210 engine carb, a very high quality unit by the way.
The main problem with the Walbro is that the carb throat is too large, this. causes a very weak DELTA P in the venturi. The throat area of the O.S. carb is 62 pct. of the Walbro.
Would sure like to see pictures of your nitro-engine carb, 8B or whatever, installed on the Moki radial engine if you'd care to share?

Bill
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Old 10-08-2018, 11:49 AM
  #4206  
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Advice please. I have a Moki 250. It will fit into the cowl of the Vailly Tempest 2 which is 1/5th scale.

Is is this a practical combination?

D G.
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Old 10-08-2018, 01:31 PM
  #4207  
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If anyone can show me a better combination I would be very surprised.

m
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Old 10-09-2018, 12:12 AM
  #4208  
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Thanks , Mick. I was just wondering if it might be rather small.

Most of the other kits for the 250 seem to be 1:4.5 or larger so I suspected the Tempest may just be a little small for what is a very powerful and heavy (mine is electric start) engine.

I have the Vailly kit so work will begin!

DG.
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Old 10-12-2018, 07:59 AM
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Help please: I have a Moki S180 with the blue ignition unit, the engine was running but when I went to restart it there were no green lights on the ignition unit. I tested that there was power going to the unit, is it faulty?
Many thanks
John
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