jairaksinen

How about if one carb feeds for example #3 cylinder through the central inlet and the rest of the cylinders had separate carbs. Would the central carb give enough oil for lubrication for the whole engine? The carbs will be very hard the adjust but I suppose there are no easy answers here anyway.

The dry sump system probably floods the lower cylinders anyway when the engine is standing for longer periods.

Jaketab

My Feedback: (2)

It seems now I must apologize for bragging about #3 running with the rest. Ran the motor again this evening and #3 was being stubborn.
I'm guessing ?? that overnight fuel settled in #3 and fowled the plug????
After several minutes, #3 kicked in and came up to temp.

Several questions if anyone would respond and help me please.

Has anyone tried different valve lash settings and plug gap for #3 cylinder ????

Would decreasing the opening of the #3 intake valve and increasing the opening of #3 exhaust valve have an affect of limiting intake of fuel and better evacuating the exhaust ???? (Help with plug fouling) (For example, .010 lash for intake and .004 lash for exhaust)

What plug gap would produce a hotter spark???? (Larger gap or smaller)

And just one more please - a 4mm head bolt dropped out of the the lower cylinder head. Any particular type of high temp thread locker recommended for the Moki cylinder head bolts ????

Thanks - Jaketab

goodinmw

Bill,
The bend in the vanes is 1 in from the necked down15/32in diameter in the intake tube, towards the crankcase. I guess I should have measured everything before I closed it up...!
Mark

goodinmw

Jaketab,
The valve lash was an option I was going to consider if the vanes didn't work. May still depending on the flight testing this weekend. One concen I have is how much gap can we afford before we start losing rods.
Following that I was going to try a restriction of some kind in the #3 tube.
Don't know enough about spark plug design to offer an opinion.
I'm sort of two faced on this whole issue- 1) upset that a $3k+ engine doesn't run like it should, and 2) enjoying the challenge of fixing my engine.
Maybe if we look back at the beginings of the turbojet development there are some parallels to draw, simply takes time to fine tune the designs and techniques.
Bottom line, I love the sound the Moki makes on the ground!
Mark

davezagwyn

http://www.youtube.com/watch?v=AbdyUgohH5s

I love my moki )

Jaketab

My Feedback: (2)

Mark,

Yes, don't want to lose the intake rod. Would just like to restrict slightly the intake mix. Maybe just .008" on intake and .005" on exhaust. Something to make that rich #3 mix a littler hotter or leaner.

What I've discovered on my 250 - Start engine and warm up. Engine misses on #3. Let engine set several minutes until residual heat warms #3. Re-start motor and then #3 kicks in when it's a bit warmer. Once #3 starts firing in mine (at at about 1500 rpm) - the temp comes up to match other cylinders.

Possible option as experiment - if you can tap a small sealable hole in #3 intake tube - introduce starting fluid into the #3 tube to get #3 plug to start firing faster???????

Anybody having a problem with head bolts backing out???

Thanks - Jaketab

BIGDAMMODELS

Hey guys...hope all had a great week-end...I went back and read a bit and feel like the problem with the #3 is more apt to happen at start-up than anywhere else....after the #3 starts to fire it seems to hold sometimes for the most part, until short runs... extended idle or idle and applied throttle...most times though the gear is pointed down towards the dirt when we get #3 fouling....now...if you look at the carb center-line you will notice that the the #3 or 7 'clock cylinder is below that line when commonly mounted, and the intake plenum for that cylinder is at the lowest point in the crankcase...when we choke the engine...(and remember that the hole is soldered closed on the choke flap..indicating a need for lots of fuel to start cold btw)....so at this time the mix is very "wet " and poorly atomized because of " flip " rpm, and of course the heavy residual would settle where?...in#3....the far most lowest point....from here the problem would only get worst with running for that cylinder...now...if we were to run that way for a couple minutes and establish overall hotter ambient temps...after the set of a bit....the excess residual may evaporate and boil...thus clearing this cylinder enough barely now for a start to run...possible explanation with jacktabs 250 post...remember that if you roll this engine 1 position at the time from mount standard, and run it,the problem will go to what ever cylinder is at the 7 o'clock position...regardless of where the exhaust pipe exit position falls...anyway you turn it..there is always one intake plenum at that low point below the carb center-line we talked of at the beginning of post...it'snot going to be a matter of restricting the fuel, as the problem then would be that it works great by doing so with a restriction, until I go inverted or change the position of #3 or the 7 o'clock cylinder...which-ever cylinder you put there in that one position..7 o'clock...any one cylinder will have an issue at the 7 o'clock position, because of design, and the fact that it is now well below the carb center-line...restrictions a no...swirl yes...the intake plenum is the most common place to swirl fuel, but because of design and the fact that this is not a v twin type block....opposed cylinder...or single for that matter.... this makes the position of the "Swirl" device to be relocated in the cylinder head, close the intake valve area for max effect, and it wil then not involve or influence the other cylinders...in any position...it would require no more than installing them if designed right, and would be the possible fix for any Moki...it would at least better overall performance by doing so even if you have no so called run issues...better mix is what betters performance...not restrictions of any type...valve lash would work if the engine was fixed in it's position..same would apply with bleed methods and restrictions of any type in the intakes...I now see a possible fix with minor change in design...give me a spell and let me find a little more info in the area we want to change...hotter spark is not the cure for the problem we thinking here...we feel we got a common area to look now because of the great post here....we gonna get it done....with a little more thought and discussing...Bill

Jaketab

My Feedback: (2)

I can confirm that several months ago, I did rotate the motor on the stand. The problem with #3 cylinder went away and another took its place in the lower position.

Jaketab

dcon1

just a stab in the dark or to play devil's advocate fellows. It seems to me that if the valve timing and lash are all correct  and the rings are all broken in and seated good,the intake pressure should be neautralized all around thus sending the same amount of fuel to each cylinder. A walbro carb. is made to function in any position ie upside down. But too much fuel residue is just too much fuel. The diaphragm in a walbro acts as a pump but the needle and seat act as a metering valve to keep too much fuel from entering the engine. This is adjusted by the spring tension on the needle by bending the tab under the diaphragm. There is a way to check this with air pressure and a guage to check what is called the pop off pressure of the needle and seat. the needle should hold about 12 to15 psi. before pop off occurs and reseal at about 6 psi and hold this pressure. But this can be adjusted to reduce a rich mixture. The only other thing that might be looked at is good air intake for the carb. Just my penny's worth.

BIGDAMMODELS

Thanks for the reply...very good info and well needed for a great understanding of the Walbro...as you stated in your post this would probably play true if the issue affected more than the one cylinder at 7 o'clock...your reply would be more applicable for the total amount of fuel available in the crankcase for all intake plenums..I knew nothing of this info you shared.....thanks again for sharing...just me thinking and mind rambling here...jaketab...good you did this and shared your findings...we now see that the issue stays at 7 o'clock...POSITION...not CYLINDER...this is the area where I feel we are side-stepping the underlying run problem at hand...the fact that the cylinder now becomes active by moving it away from there, tells me it is location and not anything more...I'll get up a few pics to show some simple ideas I'm looking at....Bill

dcon1

Maybe you could establish some kind of difference between the cylinder at 7:00 and the one at 5:00 to understand what's causing the problem. or maybe ad a connection tube between the intake tubes so they could share the fuel.

BIGDAMMODELS

Ah ha...great idea dcon1...my same area of thinking...now we can see the area of concern I'm in together here....the puzzling part is that the small amount of difference in the height of the plenums is around 1/4 in or so....it's very little if you just eye it...by slightly rotating the engine you can get both of the lowest plenums at the same level in reference to carb centerline....with the 12 o'clock cylinder at a straight up 12 position the #3 is for sure the lowest plenum in the crankcase relative to the carb centerline...what would be the first place for the cold start residual build up to cause fouling?...with normal gravity, residual settles right at the lower intake plenum in the crankcase... if over-choked cold...or a slight fat fuel mix from a little too much oil...or just slightly rich on the bottom end...etc...would be a problem for sure because of design...if you send that lowest intake plenum higher in the crankcase so to speak, with only a slight rotation of the whole engine, it should make a difference it would seem, especially now with it being at the same level as the cylinder at 5 o'clock...which has no issues running properly right...but now look...by doing so, it now throws that perfect 12 o'clock cylinder at slightly less than 12 o'clock as they recommend mounting of the engine... and makes one now at perfect 6 o clock...sounds confusing huh,..lol... but with the offset of the 12 o'clock cylinder now,( makes the engine look crooked from the frt ) it does place the lowest #3 plenum in a better place for a better mix of fuel...also... if you change the Carb mounting 180 on the main intake plenum...it directs the flow of fuel mix upwards naturally in the intake with throttle flap opening...it also puts the carb's main nozzle in a better position to atomize for cold starting...I'll get up some pics to clarify...it sounds confusing but what I'm thinking is that it is something that... #1..we are not clearly seeing as a fix between mine and yours, or theirs..., and #2... a good explanation of why aren't all Moki owners experiencing the same run issues...I feel it could be something as simple as the factory carb mountings between engine purchases or bulk runs, or something as simple as engine mount position on the given airframe we have...you hear and read so much....mine runs great...mine sputters....mine fouls....mines perfect...etc...no way it should vary this much between Moki owners...they are all Moki's from the Moki place...and should run the same...or darn near...I feel we are close to finding the difference as to why not...keep those thoughts coming...it's a simple something...we'll get it...hey jaketab,,,hadn't lost any head-bolts...yet...some mild lock-tight on reassembly maybe...clean well and apply....let me go take a few pics to try and simplify my statements...I think we on to something here that will put the issue to rest...keep it coming...Bill

fredo

I wonder if people who fly a lot of aerobatics, rolls, loops, inverted are actually flying with a more ballanced Moki runs ...[&:]

mick15

Hey guys, I have been running Mokis for six or more years, 215s and 250s of late and have never experienced the problems you are having. So before I say any more I would like you to run through, exactly, your starting procedure please.

m

BIGDAMMODELS

Hey mick15..Thanks for stopping in...please take my reply as constructive...I have no argument issues here with anyone's shared advise to a cure, but there are quite a few of us guys with issues on the #3 being wet...and wet again...and wet again...turbulators...pumps...this oil...that oil..this additive...screw here...screw there...etc...it' seems common with Moki's radial of a rich mixture...are we all so misguided and dumb-thumbed that we cant even start a 3500.00+ engine?...it's documented in so many post of the rich issues there...it's got to be something right in front of us being over-looked that we have wrong, more so than how we're starting it I believe....the issue is so erratic for the most part between reported problems...there's very few common things between peoples reported issues...but...#3...always #3...being the most common denominator...why do you have no issues?...I hope to find out....what are we overlooking..that's what we are trying to establish...please share with us anything...why is it only Moki's radial dropping #3 ?...where is Moki's factory tech?...parts on order now for months?...its like when you get this engine you are on your own...good or bad...they should advertise this up front...it would have swayed my purchase....for such a great product to make our hobby top notch with realism....you would think someone from Moki would be here to help all...offer us something...like a refund or exchange maybe...lol...this is the most money I've put in an engine to be so disappointed in establishing a steady run performance chart...and to not get one single flight since install really frustrates...this hobby is so challenging to be error free to begin with,and to suffer from engine misfire and flood since NEW in box...yes...NEW....[>:]..now the added worry of being afraid of engine misfire destroying my model and labor of love exists...never before has engine run been an unsolvable issue in my 30+ years in the hobby....especially after such a price tag....spending that kind of hard earned change for engine dependability and realism sure has taught me it's not the amount of money you spend, but the support from the manufacturer that matters in the end...hopefully we find the issue..there's got to be a fix with something somehow...we'll keep looking and trying...Bill

mick15

Well there’s a whole bunch of words there but not one even begins to answer my question?? Lol

m

dcon1

Hey bill :  Just another quick thought . You have been concentrating on mostly intake problems. Maybe you should check exhaust flow also. If the exhaust is dissconnected from #3 will it run? Just rambling.

GaryM

My Feedback: (14)

Ok, I'm going to throw something out here at the risk of being flamed and heckled. Have you given any consideration to the ratio of oil as the root of your problems. Most of your motors are new and as with every new motor you want to make sure it is broken in properly. I beleive 40:1 is the recommended ratio. I was told by Goetz to run that ratio for the first 40 minutes or so of run time then go to 50:1 . I did a 10 min and a 15 run on the ground which I did while doing taxi test etc to shake out any bugs with the plane. The exhaust tube that lines up with the #3 cylinder puked the blackest crap you have ever seen and covered the bottom of the plane. Most likely the bulk of it was assembly lube working its way out of the engine. I tuned the motor and she was still putting out a ton of junk on the plane, #3 was running at about 135. I put in a 15 minute flight and she was still a little burbly in the air.

At this point I threw out the rest of the 40:1 gas and went to 50:1, I also cut it just a little. For two gallons of gas, I think 50:1 would be 5.1 ounces. I have my bottle marked for 5 ounces and I fill to just a hair under that mark.

In my opinon, a little gas pooling and finding it way into the #3 cylinder should be able to be overcome by a run up of the motor, if the oil content is not over whelming. If the oil ratio is too heavy then chances are the plug is fowled in the heavy slurry of oil and want be self cleaning.

I think the oil ratio is very critical to the success of these motors. Look back to sometime in mid May when Jack Diaz was having problems with a 250. If I remember correctly 5 minutes or so into every flight the motor went bad. Correct me if Im wrong, but I think the fix to his probelm was lowering the oil content.

And yes my 150 is a pre 09, it was purchased in 2008, I did not put it into the air until March of this year and to date it has 26 flights and has been a pure joy to fly. I wish you all luck

BIGDAMMODELS

I don't know what may have happened to my post, but some of it is gone...maybe it timed out....after reading the piece that did get posted, it sounds like I was in a raging rant...I'll assure you it was not that...my apologies if I offended anyone...I did begin above by stating this....fill with fuel....Transmitter on...switch on receiver...turn on ignition...pull choke...1/4 throttle or less...roll-over until it kicks...( normally just a few rotations )choke off...normal start 1 to 3 flips...again...no rant...just trying to get this Moki going...it may or may not have #3 upon starting...lately it has, but it's gone after 1800rpm...we are waiting for a coil, so the fix may be it...but from new it has wet this plug dozens of times...most times the only fix is clean or replace plug...and try again....Bill

IFLYBVM2

My Feedback: (360)

Hi Mick-
Start procedure has been as follows :
Choke on
Ignition on
Pull prop through with hand until you feel the 'bump' (usually 4-6 blades)
Choke off
Engine will then start easily when flipped smartly
#3 will run until RPM reaches about mid throttle or slightly less but not at any higher RPM's
We feel there is a bad coil on that cylinder that is breaking down under load, after checking with a modified spark tester
Coil curently on order with Vogelsang.
Thanks-Mike O

mick15

Well there is a difference, I don’t know whether it has any significance or not.
When you pull the engine through to the point where you can feel it “bump” I believe encourages the problem you have with the low cylinder, as fuel can run from the plenum into the #3 induction tube wetting the plug which can be difficult to clear.

Here’s how I have always started mine. Full choke ign on flip vigorously until the engine fires, it will “run” momentarily, half choke another three strong flips usually has it running always on 5 cylinders.

I believe this method ensures any fuel that gets to any cylinder is burnt properly avoiding possible plug fowling.

JPate147

I have two Moki 250's, and I start mine the exact same way that Mick15 suggests above. Mine starts on all 5 and runs well the entire flight.

Jerry

TrevUK

Greetings from the UK,althoughI am new to this forum Iwould commentthat Ihave been operating Moki radials ( 250's)for several years now without any realproblems straight out of the box,my engines are stock units as supplied with no pumps or turbulators etcfitted,they are started as per Mick's description and run beautifully ona 40:1 fuel/oil mix,the only area requiring care I have foundis to periodicallyunscrew the air pump from the front of the crankcase to ensure it is not fouledup with grease which can block the small breather holeand/or the outlet fitting. I currently operate my twoenginesin a Composite ARF Corsairwith a 3 blade Solo prop of 32 inch dia set at 14 inch pitch which is aperfect set up,the other is ina 1/4 scale Sea Fury which after quite a bit of prop experimentation is nowhappiest on a 34 x 18 Menz - but it does have a 9 inch spinnerin place- overall would reccomend you persevere with these engines since they provide the ultimate in model airplane soundtrack.

BIGDAMMODELS

The exhaust is fine...thanks for the input..I want this same engine for my current flying Sukhoi model, but I have never been one to accept much less than perfect in the engine area...I'll have to say that when all 5 are burning she is a gem...great throttle response and idle....excellent power and very balanced...but the next time you start, it may be just the opposite...I know we get bad stuff sometimes...maybe that's the case here hopefully...the coil does lose fire above 1800...it may have just been bad from the beginning...the oil mix is correct...the initial run was done most as you describe, but no flight time was given....26/16 used for break-in...I used no tach at break-in because it was said that the engine has an over-rev protect and this was the recommended break-in prop...and she sounded great, although a little sloppy from the extra oil...I never gagged her for any length of time...was satisfied really for the most part...get her installed finally....not until I put the 3 blade 25/16 on was it tached and checked for recommended rpm for this prop....it was here we first noticed the rpm was lower than recommended by about 7 to 8 hundred rpm...temps were checked and the #3 showed cold...engine run smooth even with the underlying #3 issue...since, it's been a battle to find a common start or run cycle...wot rpm...we made a spark tester and found that the spark died on #3 as soon as 1800 was breached....it would idle for-ever with no issue...but as soon as it got to 1800+...cold #3...you could reduce throttle...#3 running again...I repeated this several times...any needle adjust during this time would effect either too lean or rich with little adjustment needed either way...50/1 oil btw....it sounds like a bad coil from the start to me, or one that failed from the initial fat oil run maybe...what's got me scratching is the next time you start, it was 5150rpm at wot and you've done nothing...held it fine until the throttle was reduced to idle and advanced.... again...cold #3....clean or replace plug...stay under 1800...and it runs great...I come here looking for info as this is the Moki info place...I was searching for common run adjustments...oil types...a possible solution of sorts....they are so varied between engines seems like....then I see turbulators...fuel-pumps...are these needed for a secure run I ask myself...were they designed for #3 cyl cure, or to make all cylinders better...my engine experience will never argue that atomization is key to performance at all settings for any type engine...I can't use the available turbulator because of model design reasons...does the pump cure the issue or just fix the stock fuel pumps weakness of delivery at cold start.....mick...are you running a pump?....Bill

mick15

Yes Bill I am running a pump, but more from habit than necessity.

m.