Thanks for checking out this thread. I have been having trouble getting my Moki 1.8 to run consistently. Here is the poop:


The Setup:

1. Moki 1.8 with one gallon of fuel through it.
2. Bisson "sport" muffler with muffler pressure.
3. K&B 1L glow plug as recommended in manual.
4. Fuel: Byrons FAI castor/synthetic blend.
5. Airframe: Morris Giant Su-do-khoi.

Symptoms:

I would have to set the high-end very rich on take-off to avoid sagging during vertical manuevers later in the flight. During take-off I would sometimes not have a clean two-stroke it was so rich. It would break into a clean two stroke during verticals early the flight if pulled to the vertical. As the tank burned down I was able to get a clean high-end in level and vertical flight. At first I just thought this was "new" or "tight" engine behavior. However, after a gallon of fuel it has not changed at all.

My Guess:

The engine had a fuel feed problem resulting in inconsistent mixture as the fuel tank level decreased. I had thought that this was improbable because of the excellent placement of
the fuel tank. It is directly opposite the engine and exactly on the centerline of the carb. See my website at http://home.flash.net/~jecramer/giant_su_do_khoi.htm for the engine/tank arrangement. I can't imagine it getting any better than this!

Solution:

I mounted a Perry VP-30 regulating pump using crankcase pressure.

Results:

Horrible. At first I could not get the engine started because of the amount of fuel the pump was supplying at idle - it was really flooding. I leaned the idle, got it started, but could not transition past 1/4 throttle due to fuel starvation. All combinations of high-end, low-end, and pump volume adjustments were tried but nothing would provide a consitent run. I either could not start it because of the excessively rich low end, or I could start it after leaning the low end but could not transition to a high-end.

Suggestions?

Try a Cline pump as recommended in the manual?
Go back to muffler pressure and try different glow plug or fuel?
Sell it on Ebay and get a gasoline engine?

All advice is welcome! Thanks!

It took about 4 gallons through mine to get it as good as it probably will ever get. The trickiest thing in my case was that dang low-speed disk. Tuning the Moki turned out to be the most trying experience in R/C for me.

I've tried plugs: OS8, OSF, Enya3 (the best, very hot)

I've tried fuel delivery tweaking: Large diam. tubing, drilled-out clunk, even a check valve! (No change)

I've tried fuels with/without nitro from 0 - 10% (No significant difference although the needle design likes FAI)

At this time:

1. No deadsticks, GOOD!

2. Transition on the ground good; however it sucks big time in the air! As soon as the plane speeds up during the takeoff run, it sputters as you advanced that throttle! Figure that one out!

3. As soon as it is in the air anything below 3/4 stick is way rich, and if you roll it inverted it becomes richer. HOWEVER, IF YOU LEAN THE DISK ANY MORE THE ENGINE WILL CUT ON TRANSITION!!!

4. EXCELLENT IDLE

5. EXCELLENT, MUCHO POWER at the top! (Hovers a Sig CAP 231EX!)

6. Since it doesn,t deadsticks I will keep it.

Wow!

This is getting to be such a common complaint, that I no longer feel lonely about it.

I and many others have also been fighting a 1.35 with the very same symptoms. I think it was Bob_n, that adapted a OS 7D carb to his, and all the problems went away for good. I personally really hate to think one should have to buy a $65 carb from another manufacture, to end up with a great running Moki. The most irritating thing is, how the dist. brags up the Moki smoothness and transition at all throttle speeds. "The Throttle transition characteristics are without equal in any other model engine". Maybe I just take that quote the wrong way

All that aside, now on gallon 7, mine is no longer dieing in the air, and seems to be showing signs of improvement with every tank I run through it. It seems to be more and more tolerant of the overly rich midrange condition as it gets more broken in.
The fact that this thing runs good till it gets up airspeed, sounds like that very large Moki air intake could be the cause of the problem. In order for the engine to go rich, there must be a vacuum forming over that air intake. I've also noticed a lot of side slop in the carb barrel. When that thing moves at will, there must be a very uneven fuel flow through the low speed groove.
It just seems like a very crude carb setup to me.

Hate to sound so negative, but this engine has been a very unpleasant experience. I was just expecting so much more. Live and learn I guess.

Kevin

I forgot to mention, I did try the Cline regulator, and it actually made the rich midrange problem worse. I really think the engine gets fuel fine, it just seems to be a metering problem while the engine is moving forward. Strange

Kevin

I have the Moki 1.80. I run straight Methonal(alchy) from the go-kart shop, mixed with 17% Blendzall.
OS type F plug.
Dubro 24oz. tank, running medium tubing.
Cline regulator.
Tank is on CG of plane, Goldberg Sukhoi.
18x10 Pro-Zinger prop, tachs at 7800+/-.
Hand starts in about 6 cranks or so, usually, it likes to start real wet. Very slow smooth idle for a glow engine.

What size tubing are you running from your tank to carb?, and what prop? I found the straight alchy runs very good, with good idle, instant transition, all that jazz. I couldn't find an FAI fuel that would run the way I know it should, so that's when I found the cart-shop. I was also using muffler pressure for a bit, and didn't get the consistency I wanted, so I put the cline regulator back in, after cleaning it up. That fuel and the Cline go hand in hand I think. You do need to keep that regulator clean, and free of all debri. Even micro stuff can alter that regulator. Mine works really well as set up. That tank/fuel system though has to be perfectly sealed. It runs at 8 to 12lbs of pressure, and thats quite a bit. I forget once in a while after a run when I go to fuel again, and it will shoot a good geyser.
It pulls that 14+lb plane absolutely out of site vertically. I wish I had other answers, I will ponder this one, and keep checking back though. Good luck

I have had three Moki"s and have yet to get one of them to run right. I had a new one and two that were well broken in. Their owners were selling them out of frustration. I lost count of the deadsticks! In my opinion I think the venturi area is too large. Look at the OS 160 it has a restricter. The Cline pump helps in some cases, but if the engine was properly designed, wouldn't be necessary. I want to fly not nursemaid an engine. There are too many good ones out there to waste time with a lemon. I have seen some that run good but at what cost in time, frustration and after market gadgets.

Thanks for sharing your setup!

I am running "large" fuel tubing all around and using an 18x8 propeller. The muffler pressure setup that I originally had was flyable - just not optimal, in fact, far from it.

I can certainly try a Cline regulator, but I want to gather some more advice before I drop another $50.00 on this beast.

Thanks,

jc

I took apart the needle assembly and found some hard congealed junk inside the inlet banjo and around the needle orifices. I suspect it came from the factory that way. It was too hard to have just been castor gum. I have not tested it yet.

Regards,

jc

Adapt a small carb (make a apapter) and use a small wallbro carb like on a G23 or a carb about the same size from a chainsaw. They hane a built in pump which can be run from crankcase pressure. May have to tap backplate. Will not need muffler pressure, or a cline pump. If anyone can add more that has seen this done, give us your results. Thanks Captijohn

I have a Moki 2.1 that I had the problem of going rich after take-off. Since I was using a cline system I contacted Bill Cline for advise. He told me to mount the regulator so the vent in the regulator is pointed toward the rear of the aircraft. That cured the problem. The airstream was pressurizing the regulator.
I also found the best plug for me is the OS type F four stroke plug.
I use FAI fuel with all castor lube.

First Off: One gallon through the big Moki's is not enough. Mine started running real well after 5 gallons. I have had the 180 on three different planes over several years and it still starts easy and runs well.
I, too, had the Moki on a giant su-do-khoi and it was a good combination. Lots of power to weight.
You must use the large diameter tubing from the clunk through the carb. You may have to drill out the clunk as well. The su-do-khoi used to come with a relative small profile tank (8 oz I think) and these small tanks have small clunks.
I have tried the moki both with the cline regulator and without it. When using the cline, you must still use the large diameter tubing on the 1/2 inch section of tubing between the regulator and the carb. You can use any tubing you want everywhere else.
Jim Gerrard modified my carb when I first installed the Cline system. He said the early (pre-1999) engines were NOT designed for the cline system (under the cline system, the carb sees zero pressure in the fuel system).
Later carbs were designed to use either muffler pressure or the zero-pressure cline system.
Here are the pro's and con's of the cline system: With the cline system the needle valve setting is constant throughout the entire flight in any flight attitude. Very useful in hovering, etc.
The con of this system is that every once in a while it gets some dirt in it and it "sticks" open and floods the engine out. You must keep the fuel very clean and use a filter before the regulator.