Primi

Hello Moki owners,

maybe somebody could help me with my problem with a Moki 100VBT it is flat two cylinder very similar to the five cylinders. What happen was from one flight to the other the engine cut out in the air after about five minute flight. As I found it over heated and blocked. After landing the engine cooled down and I was able to turn it over again. After this incident I checked the engine, valve clearance, cylinder heat, plug etc. could not find anything wrong. I gave it a test run again and the same thing happen, but this time I measured the heat temperatures in idle one cylinder was at 55deg C the other 90deg C rising. At 120 deg C I stopped the engine and changed the needle settings to rich and back to lean, no difference.
If somebody could tell me what else to check or what it could be, the engine was running for about 5 hours in total, should be run in by now, I always used redline full syndetic 30:1.

I own also a 180 but will not fire it up before I know what and why this happens.

Any help is very appreciated, Thanks

reyn3545

If it cut out twice after about 5 minutes, and it was running without any sign of problems prior to the cutout, I would look at fuel supply and heat. If the motor ran until it got hot enough to seize, it would probably not have started and flown again, so heat is probably not the problem. I would check inside your fuel tank and see if the clunk line has separated from the copper tubing or something like that.

Primi

Thanks for that I'll check this as next, I do checked the fuel supply and open up both needles, but when it stops there is still fuel tripping out of the carby. What worried me was the big difference in heat on both cylinders! The engine has definitely seized because when it stopped I was not able to turn it over till it cooled down!

reyn3545

Wow.... then you have a bigger problem than I thought. Is the motor inside a cowl, and do you have baffling to force air through the cooling fins? Also, do you have a large enough cutout in the bottom of the cowl for hot air to escape?

Primi

Yes I do have baffling in the cowl and cooling was always sufficient never went over 100deg C

Maxam

My Feedback: (62)

Primi, There is unequal fuel distribution to the cylinders. At full throttle what are the differences to the cylinder temps? Can the carb be rotated. Many do not realize the fuel mixture is not equal in the carb choke but more off to one side. You would be amazed at what the distribution of the mixture can do when a carb is simply rotated. If it cant be, can you remount the carb 180 degrees?? -Tom

Primi

Maxam, it looks like you could be right in idle where the temp is 100deg C at the front and 60 on the back but at full throttle the temps increase equally to 130 till it seizes. But why it was working before and not now, what could be blocked? after the needle there is not much more which can change the fuel distribution?

Maxam

My Feedback: (62)

And you are not too lean on the high end??

Primi

Ok today I cleaned the carby checked the needles etc. found a bit dirt in the filter cleaned all out and looked so far good. After I started the engine the same happens again, only this time the temperatures were on all cylinders the same. checked the carby and fuel was running out of it so there should be enough fuel also turned the needle 2 1/2 turns out to supply enough fuel. When the engine stops the compression is very high looks like the a seized engine maybe it is, it is hard to turn it over so I don't force it and wait till it cooled down. The temp only climed up to 120deg C before it stoped.
Checked also the fuel tanks and lines all good the clunk is working and fuel lines are OK.

Any further suggestions?

Thanks

Maxam

My Feedback: (62)

While the engine is running, can you adjust the high end needle and make the engine go rich and therefore be rough and smoky??? If so the there must be some other problem like a scored cylinder.

mike31

My Feedback: (67)

MOKI has great performing engines. I wish I had a piston for mine. 61LS! Any help would be appreciated.

Primi

I adjusted the both needles during running and it did run rough and lean again but still cut out very quickly, but also I missed the smoke when it was rich. Maybe there is still a fuel supply problem. I take the carby out again and check all bores if not one is blocked. This is now the best theory. The cylinders looked absolutely clean and shiny nothing to find.
Thanks Maxam this will take up to the next weekend.

GeorgiaFlyer

Do you spray oil on the valve rockers? could be a sticking valve.

Primi

Yes I do before each days starting and check also during testing that non of the valves are stuck. I had stuck valves before and there was every time also some miss fire just before, but not this time.

SJN

Anybody know what size 4 blade prop would work on a moki 180 ?

A Fiala 24/16 maybe ?

Reccomended 2 blades are 26/16 and 28/14 stated in the manual.

GeorgiaFlyer

I am currently using a Fiala 26x18 two blade and works very well. Even with the 18 pitch the 180 handles it very easily, on ground RPM is 5200, so I make sure to limit how much throttle I give it in the air so not to over rev on unloaded prop. I want to get a four blade for it. Thinking about a Solo 26 with adjustable pitch. Seeing how easily it handles the two blade 26x18 I think it would handle the four blade 26 with a little less pitch. Only problem I got is that Solo is not taking orders right now as they are moving. :-(

SJN

I would love to order a solo prop, but once shipped, and with customs fees and local taxes are paid, it will cost about 1000 US dollars in total for a 4 blade prop.......thats just too much.
I cant realy use a 26" prop, as I will get prop strikes with my stock short landing gear.... :-(

It says that there is a rev limiter in the ignition module, so you wont destroy the engine.

GeorgiaFlyer

Yea I put in longer landing gear on mine so plenty of clearance for a 26" prop
I have read that there is a rev limiter on the new ignition modules but also read that you should not rely on that to kick in, so be careful not to over rev this motor

Growler84

My Feedback: (8)

Aircraft International (US 3W dealer) lists the Biela 23 X 14 4-blade as a Moki 150 propeller. They list a 28 X 12 4-blade for a "180" but no mention if thats a Moki 180.

aircraftinternational.com

Scalercer

My Feedback: (1)

Thanks to all who have contributed to the discussion so far. I just purchased my first Moki 250 & really appreciate all the wisdom of other Moki owner/users. Attached is what I have gleaned from the discussions so far.
Cheers,
Mike
Care &Maintenance of Moki Radials
Fuel- Lowoctane pump gas will work, non-ethanol 90 octane or higher works better.Remember that ethanol hates rubber, plastic & aluminum. Enough said!
Oils &lubes- "use 30:1 Yamalube or Mobile T2, and don't stray from therecommened ratio."
It sounds like others have usedKlotz & other synthetics with success.
You can run 80 grade gear oil in thehousing, instead of grease to eliminate the breather tube clogging. Also, only use clear tubing for thebreather.
Tri-Flow 20027 is recommended forpush rod lubrication, but white lithium grease that is used on fishing reels may work better.
Valveadjustment- Scott Prosser recommends .007
Mick Burrell’s procedure for adjusting valveclearances, rotate the engine until one valve is fully open, and then rotate360 degrees. Undo the locking nut and gently tighten the screw until it touchesthe valve, you should feel the pushrod just nip. Back off the screw ONE flatand tighten the nut.
Factorysettings are always a good starting place.
Red Loctiteis recommended on the exhaust ring flange nuts. Check them regularly forlooseness.
DO NOT EVEREXCEED MAXIMUM RPM’S. Bad, expensive things will happen to your shiny new Moki.
Baffles- Yesif inside a cowl. Relieve a little area around the exhaust tube for bettercooling.
Not necessary if out in the open.
Ignitionbatteries- consensus is 4.8 to 6.0 v & 2400Mah to 4200Mah batteries willwork. Some run regulators & some don’t.

Primi

Gent's any further suggestion for this problem?

I did again a few tests today, first checked everything possible carby, tank, valve clearance, spark plug (replaced as they were black and grease). It started always easy but only runs for a few seconds then the front cylinder (left) is getting hot up to 120deg C (250F) were the right cylinder has only 60deg C on it, then is stops.

Taken the head off I found everything covered in black oily grease, I cleaned all up and turned the pistons a few times over and found that the black stuff came from the crank case, taken the cylinder off I found a lot of oil in there. Now I reduced my mix to 40:1 which gave me a little bit better running results but after a few runs the same game again.
Why only the left cylinder is getting hot, the cylinder look the same, compression is same, rings are ok, so what else can it be?

pc55bomber

Hi all

Trying to get my unflown Moki 150 to run properly. Have read thu this entire thread and gleaned as much info as possible, thanks to all.

Wanting to run the engine as stock as possible and as we all know cyl #3 does not fire at all.
So decided to get the Rainbow tronics ignition from IBCINYORC but it came without any instructions.

Have trialed the ignition, Cyl#3 now runs but Cyl#4 doesn't, it,s still only running on 4 cyl's.
Running the ignition on a 3S lipo (11.1v nom) directly plugged into the ignition, no switches yet,and after the red light initializes, it then goes into a blinking mode every 2 seconds, the engine will run but not well.
The red light has only ever come on solid once for a short time and the engine ran on all cylinders, then it just quit the light was out, replugged the battery in and it started its normal 2 second blinking.

As I don't have any instructiuons, I don't know whats going on.


Does anyone have a copy of the instructions ?

Could my ignition be faulty??

Any help would be appreciated.
Thanks
Paul

pc55bomber

Update,
Have my answer and a copy of the instructions directly from Uwe.
Had it running yesterday stock standard on 5 cylinders until throttling up, then back to 4 so will do more tuning.

Cheers
Paul

DrScoles

My Feedback: (18)

Battery question. I have a moki 250 with the new ignition and the fuel pump. I have two 2500 A123 packs, is it safe to run both the pump and ignition on one pack, or should I split them?

reyn3545

I would fly with separate batteries, then charge both batteries and see how many total milliamps are going into each battery. Combine the numbers, and that should give you a good idea of what you'd pull out of a single pack if the ignition and pump were combined. There's plenty of available amperage in a single pack to support both the pump and the ignition, so you shouldn't worry about that.