The first step to recovery (engine break in)

Kiddo... as in kid.

Hmmmmmm...... So "kiddo" has nothing to do with the question asked about "recovery"..

"Sure-starts" are usually, well, easy to start.  Suggest that it was simply flooded with excess prime.  It helps to blow out the excess with your mouth.  Today most LHS fuels are not suitable for !/2 engines.  Try Sig 25 or 35.  Don't go by nitro content alone.

Used engines are very ofen gummed by castor oil residue.  Disassemble it and clean it throughly and, above all, be patient.

SD

Cox engines need little or no break-in, if they don't start like your used one something is wrong and troubleshooting should be done.  

It sounds like you might be using modern fuel with only synthetic oil in the fuel. That is not enough to seal between the cylinder and piston when there is a poor fit, you need castor oil for that.

Thanks for the replies.

Dave: Sorry for the kiddo confusion. Having her along and not being able to fire things up was frustrating.

The fuel is 15% nitro, 10% castor, 10% synthetic (don't have it in front of me, so don't know the brand). To be safe, I added 6 oz of castor which would yield nearly 15% total while only dropping the nitro down to 14.5%

I did order some of the SIG 25% Champion fuel.

Again, thanks for the help.

John, I'm going to assume your fuel is correct as others suggest might be the culprit. Randy Ritch the owner Ritch's Brew Fuel makes hands down the best fuel available on the market today. HE'S IN YOUR BACKYARD. I wouldn't even consider using another fuel and call Randy and order fuel.  http://www.ritchsbrew.com/rb.html  As for the Texas temps, it can get quite hot. I personally would bump up the nitro although this isn't a factor as to why your engines were as problematic as you claimed. How hot was it when your trying to start this engine? While I offer a few suggestions, start with the simplest things first and go from there. I somewhat listed them in a order I would look at if I was having the difficulties your experiencing.  You have a lot of missing info for a good diagnosis. Many times however, I've seen problematic starts due to leaking glow plugs due to improper sealing surfaces or bad head shims. New head shims may require repeated tightening until they become seated. This will cause hard starts every time. When you checked the plug like you claimed, how bright was it glowing? If it's mottled or all coils aren't glowing , the plug is suspect requiring a new plug or batteries. What kind of battery are you using to start the engine? Funny thing here is that this seems to be non related to new or old but all of the engines you tried to run.

What kind of clip are you using? A stock Cox clip while it does work is very poorly designed as the wires are too short and the gauge of wire aren't  properly sized. I use some pretty heavy heater cord and a series of 6 D cells for a starter battery. Improperly lit glow plugs will cause problematic starts due to drowning out especially if over primed.

You mentioned running the Sure Start. This engine doesn't come with a tank. Is this engine in a plane or on a test stand? What kind of tank are you using. How long is the fuel line from the tank to the engine? Has the tank been pressure tested underwater? This is true of the Bee as well. While it appears that your engines wouldn't start at all or took countless tries, here's a few things to look at as well.  Much of the rough running can be contributed to air leaks.  I would consider using a syringe with the needle valve closed down and with one finger over one nipple and a syringe pressurizing the other nipple check for leaks.  Most leaks will show their ugliness the second you pressurize. Backplate screws will leak, needle valve will leak, venturi -o ring will leak internally. Many many things are a factor here which makes it very if not impossible to diagnose your troubles. Have the engines been taken apart by yourself? Were all the gaskets replaced? I would certainly do a shotgun blast of the entire engine or engines. Replace reed valve  and test the reed valve prior to fully assembling the engine. This means that a syringe placed on the venturi with it's plunger retracted should be able to pass air by pushing on the plunger and not being able to retract the plunger due to the reed valve sealing properly. If you can retract the plunger, the reed isn't working and regardless  of new either needs to be replaced or flipped over and tried again. Ken

I use 2 NiZn batteries in parallel 2800mah ea for 5.6A they are nominal at 1.6v not 1.2v as a nicad or nimh or 1.5v as a dry cell and the NiZn's charge up to 1.93v enough voltage to fire up any engine. Another solution is a adjustable step down voltage regulator using a 12v 7A starter battery you can dial in a low orange glow allowing start up's and running with lower nitro fuels. Ref: Ofna Glow Plug Cable w/12V Driver 10216.



 I buy at least 25% nitro for starting all my cox engines with min. 20% castor blend. I say at least 25% nitro as the bottle goes a little flat over time.

Being simple of mind frugal I still prefer two D-cells in paralell.

SD

Ken,
Thanks for the suggestions.  I will get some Ritch's.  Not only is he in my neck o' the woods, he is closer than the LHS. Sorry I haven't provided much information... frankly, I was so dumbfounded I couldn't seperate good data from bad.  The temperature was in the mid 90s.  On the Bee, I had just replaced the head, but I didn't replace the copper gasket.  That could be something I consider doing (On the used engine, I noticed on the first run that the head was leaking, fuel 'sweating' out.  Opened it up and found the gasket had been installed incorrectly.  Replaced it, and the sweating stopped).  The element was glowing bright red, bright enough to see it easily in the afternoon sun without shading it.  I am using 2 D cells in parallel which were fresh.   The clip is one of the black 'clothes pin' style:  http://coxengines.ca/cox-glow-plug-clip-tweezer-style.html.

The sure start is using a  3/8 oz Perfect triangle tank:  http://coxengines.ca/3-8oz-fuel-tank-for-cox-engine.html.  The supply tube (the one at the apex of the triangle) is parallel to the crank shaft and at roughly the same level in level flight (I eyeballed it when I mounted it, its within 1/8 of an inch).  It is mounted on the right/outboard side of the profile fuselage.  The fuel line is about 1 3/4 inches.  I have not pressure tested the tank, but will do so (the Bee's tank too).

I have not torn down the engines.  They were purchased new, and I thought opening up a brand new engine was unwise... I'm rethinking that.  I will pressure test everything as you suggest.  

Again, thanks for all the help!

John

John,how was the head gasket installed incorrectly(creased,off to one side)I would just snug my heads up not putting any real torque to it until I figure out they were leaking.

Rat,
The gasket was installed off center and looked like it was partially caught in the threads between the head and cylinder.  The threads on the head and cylinder appeared undamaged, so I installed a new gasket and she seemed fine.

This was on the engine I bought used. I tried it before I tore it down just to get rough benchmark before I started fiddling with it.

Rules of thumb :

leaks are bad.  

Dirt is bad

1 shim/gasket per 10% nitro (rounding is adjusting, so 25% usually takes 3 gaskets)

At least 1 gasket has to be "new" as the gaskets work harden.

Flooding is bad, if it sizzles like bacon it is flooded (but sizzle also shows prime, so sizzle can be good)

Triangle tanks are bench empty at 1/2 full

So:

Leaks are bad.  If the reed leaks, if the crankcase leaks, if the head leaks...ALL BAD.  Add fuel to critical locations and check for bubbles.  Head leaks are easy since fuel holds in the fins pretty well.  Other leaks are less easy.  Using aluminum safe sealant to seal gaskets and screws is good.

Dirt is bad:  Dirty fuel, or a dirty fuel system, or dirt aspired through the intake, or dried oil, or any other source of dirt can jam a reed and allow it to not seal.  Flushing the engine via flooding though the venturi with clean fuel MAY fix a minor case of dirt in the reed, but it also might not.  After-run oil and putting engines up clean is about the only protections.  Dirt causes tear downs...

1 gasket/shim per 10% nitro content: pretty self explanatory.  You should have (need) 1 gasket.  Every 10% should have another gasket.  Hot weather will require less compression than cold as that will retard timing when the engine wants to fire more readily.  different heads are higher compression than others too, so every head needs to be evaluated separately (yes, QC means that the same brand head should perform the same as the replacement of the same brand.Switching brands of heads can change compression.)  25% nitro typically uses 3 gasket shims, use of 5 or more shim gaskets with high compression heads is not unheard of on 25% nitro fuel.

1 new gasket minimum:  Crush (deformation of the metal) is necessary to get a seal.  It might be better to use all new, but reusing gaskets is common, I would hazard to say most people reuse head gaskets.  The gaskets must crush to seal to the cylinder, head, and each other.  If the gasket is hardened it won't crush, and won't seal.  This also means that as the engine thermal cycles the head can come loose.

A perfect head on a clean seat will seal without a gasket, but the compression is too high even for no-nitro fuel.  Lapping the head on extra fine sandpaper may be necessary, use a piece of glass on a stout surface to support the sandpaper.  "Wet" paper used with oil or water best.

Flooding is bad.  It can break an engine if it is too severe.  A sizzling engine is probably too wet to start, but it might also be 1 flip away from being at the right prime.  A flooded case can cause problems too, spraying too much fuel into the chamber to burn.  For inverted mounting a flooded cylinder can fluid-lock the engine and do severe damage to the engine, but this is happily not a problem for upright or sideways mounting. Try closing the NVA and flipping till it barks, then won't bark and start over with fresh prime.

Try priming the exhaust ports with the cylinder closing the ports.  When the engine cycles a more proper quantity of fuel will enter.

Triangle tanks are rigid, as are bee tanks.  With CL setups when the tank is 1/2 empty and there is no force of turning (centripetal) to keep the fuel on the pickup.

Summing up:

Flooding, dirt, and leaks are bad.  Set the correct compression for your fuel choice.  Prime carefully.  Pay attention to the fuel tank position so the pickup is wet.

Hope this helps.

Phil

Phil explains the leak situation very well without being overly wordy as some are wont to do.  It's not that complicated.

Nice job Phil!

SD

SuperDave wrote:Phil explains the leak situation very well without being overly wordy as some are wont to do.  It's not that complicated.

Nice job Phil!

SD

If complicated (well, more like complete) is wanted, the Gibeault Mouse Race Program link on this page should be consulted

http://coxengines.ca/engine-and-fuel-guides.html

Phil

Thanks Phil!

That shim information, 1 for eat 10%, is something I haven't stumbled across before (sure I heard racers use lots of them with super hot fuels, but I never realized it applied to the lowly bee). Thinking about how the engines behaved, I fully believe this is a contributing factor.

I've ordered shims and gasket sets. I won't be able to play with them until Wednesday, so hopefully I will get the goodies by then.

John

If you are severely over-compressed starting might be difficult. Slightly over-compressed is not a big deal for starting. One gasket for 15% nitro might be right, 2 might be right also. Got to do back-to-back runs with both setups.

Ran fine last year but not this year is likely dried oils gumming the reed. A few hours before trying to run the engine prime it an flip a few, then wrap the engine in a plastic bag to stay "wet" so the old oil dissolves. Might help, might not. (It will also test the fuel-proof nature of your paint)

Phil

The number of head shims depend first of all on the the type of head used. With the cox low compression I've never used more than one head shim. The TD heads and in particular the later Merlin insert types do require several head shims.

One thing that I have note with the sure start cylinders is that they are not as tight as the older true cox engines where. It is therefore important to have castor in fuel, not only to save the piston and conrod, but also for a good seal between cylinder and piston.

If the engine is wet and doesn't fire then there is not enough power to the plug. They should at least pop/fire when they are wet.

Even with the low compression head added shims may be of benefit. It takes repeated runs with a means of determining how well the engine is running (tach, timed laps, or otherwise) to decide if the compression is set right for the fuel being used.

Phil

Cleaning the sure start, I found one potential problem:  bad? reed.  it seems bowed incorrectly toward the crank case.  see pic



Blowing from the crank case side a had no more resistance than sucking.  seems to me that"s a bad reed.  Am I correct?

edit: clearly I am bloggidly challenged. I can't seem to post the pic. If it were there, it shows the reed bowed away from the orifice.

It should not bow away from the sealing surface, it is better the other way around as it will always open anyway due to the pressure differences.

The reed should not bow at all sitting in place. I suspect contamination of the reed seat, or hanging up on the reed clip. Take it all the way down and clean it carefully and reassemble. If the reed is creased then it is bad. Reeds are surprisingly tough...be careful all the same.

Rubbing alcohol, denatured alcohol, or fuel works well for cleaning.

Phil

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Okay, finally got the pic to post. I'm slow, but trainable.

I got it out, but it is spring (bent), so I will wait for the rebuild kit to get here.   Is there a trick to installing these?

John,

That reed is damaged beyond repair. Toss it, as that engine will never run with that reed.

In regards to cupping of the reed, it only happens over time and is barely visible to the naked eye.

The one shown in the picture is either too large or very poorly installed. It should lay flat and move freely within the retainer.

Did you remove the retainer before taking out the reed?

Ron