Engine problems

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Robert Roland - 29 Sep 2008 14:25 GMT

I have a Raptor 50 V2 with an OS 50 SH (non-hyper).

For a while, I have been feeling that it is a little low on power, but
haven't worried too much about it.

This weekend, I was flying as normal, the engine produces plenty of
smoke, and even coughs briefly into four-cycle now and then. The
governor, however, seems to have problem keeping the head speed.
Particularly on fast, long descents, the engine seems to overspeed
slightly.

So , I land and turn the needle in a couple of clicks. Fill the tank
and try to start. The plug is burned out. I replace the plug and go
fly again. The brief four-cycle coughs have disappeared, and
everything seems normal.

Suddenly, during a hover, the engine quits. When I go to collect the
model, I notice the engine seems to radiate more heat than normal, so
I do the "wet finger test": It sizzles. On attempting to restart, I
notice the plug is burned out again.

To me, it seems I have symptoms of both too rich and too lean mixture.
Is it simply time for a new engine? Or have I done something wrong?

I know I should do a test flight without governor, but I ran out of
plugs and time, so I called it a day. Depending on what you experts
say, I may put the helicopter on the tests stand.

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RoRo

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John Ferrell - 29 Sep 2008 16:16 GMT

I am a Heli beginner(wanna be?) but I have a lot of Glow engine
experience.

The "sizzle" and quick plug burnt outs are both indicators of a lean
mixture condition. I would suspect:
Needle loose or leaking air
Exhaust pressure blocked or leaking allowing low fuel pressure
Worn engine bearings

Once it starts running lean the condition seems to just get worse.
Keep at it long enough and the heat will get the piston & liner as
well.

John Ferrell W8CCW

>I have a Raptor 50 V2 with an OS 50 SH (non-hyper).
>
[quoted text clipped - 23 lines]
>plugs and time, so I called it a day. Depending on what you experts
>say, I may put the helicopter on the tests stand.

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Beav - 29 Sep 2008 16:26 GMT

>I have a Raptor 50 V2 with an OS 50 SH (non-hyper).
>
[quoted text clipped - 8 lines]
>
> So , I land and turn the needle in a couple of clicks.

Which will only serve to exacerbate the problem. If the engine is
overspeeding when the load is removed, then eaning it out will make things
worse. It sounds like your throttle linkage andgovernor setup needs
attention.

>Fill the tank
> and try to start. The plug is burned out.

Too lean and you've overheated the motor.

>I replace the plug and go
> fly again. The brief four-cycle coughs have disappeared, and
> everything seems normal.

This still sounds too lean.

> Suddenly, during a hover, the engine quits. When I go to collect the
> model, I notice the engine seems to radiate more heat than normal, so
> I do the "wet finger test": It sizzles. On attempting to restart, I
> notice the plug is burned out again.

Too lean.

> To me, it seems I have symptoms of both too rich and too lean mixture.
> Is it simply time for a new engine? Or have I done something wrong?

You've probably f.cked the engine, but maybe you got lucky. I don't know
what fuel you're using, but if it's the green shite (CrapPower) then bin it
and use something with a decent amount of oil in it. I get my fuel mixed and
never use less than 20% oil, but I prefer 22% so I never experience your
problem with my own motors, but I've seen hundreds over the years and it's
always centred around the same thing. Too lean, shite fuel and inappropriate
use of a governor, or a combo of the three. One thing to check before
binning the motor though. Is it varnished inside? This is a by-product of
just a couple of lean runs or crap fuel (not enough oil) and if it is, a
simple cure is to remove the varnish and that's best done by dropping the
piston and liner in a pan of boiling water with added biological washing
powder (NOT non bio coz you'd wate your time trying it).

Keep adding the washing powder until the water is cack brown and the engine
internals are shiny bright again. It works.

> I know I should do a test flight without governor, but I ran out of
> plugs and time, so I called it a day. Depending on what you experts
> say, I may put the helicopter on the tests stand.

If your engine is overheating (and it patently is) and slowing down by even
the tiniest amount, the governor will do it's damndest to stop the revs
dropping no matter what the REASON for the drop. This can be because it's
partially seizing, but the gov doesn't know that, so it opens the throttle
and produces even more heat. Result is a dead plug or two followed by a dead
engine.

You should NEVER use a governor on a new engine for this single reason, so
if you decide on a new one, don't use the gov until it's been run-in
properly.

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Robert Roland - 01 Oct 2008 17:50 GMT

>Too lean and you've overheated the motor.
>This still sounds too lean.
>Too lean.

OK, but what about all the smoke and the occasional four-cycle? It
seemed it was plenty rich, based on those signs.

>You've probably f.cked the engine, but maybe you got lucky.

How exactly does the engine get damaged from lean running? Is it
excessive wear on the piston and cylinder?

>One thing to check before
>binning the motor though. Is it varnished inside?

Well, I took it apart yesterday. The top of the piston is dark brown,
otherwise, it's all nice and clean.

But I think I have found the problem: The rear (or is it lower on a
heli?) bearing is completely shot. The races look terrible, and even
the balls are visibly damaged. The piston and the ring have scratches
that can easily be felt with a finger nail. The cylinder liner looks
good, though. The glow plug has almost no coil left at all. Only short
stumps left at each end.

It seems the cause of the damage was rust. The bearing had clear signs
of rust on the side of the races. The front (upper) bearing, though,
was like new.

Bearings, piston and ring would cost about half of a new engine, so
I'll simply get a new one.

Now, the big question is, of course: How do I prevent my new engine
from rusting?

>simple cure is to remove the varnish and that's best done by dropping the
>piston and liner in a pan of boiling water with added biological washing
>powder (NOT non bio coz you'd wate your time trying it).

Washing powder for washing clothes?

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Kevin - 01 Oct 2008 19:16 GMT

>> Too lean and you've overheated the motor.
>> This still sounds too lean.
[quoted text clipped - 30 lines]
> Now, the big question is, of course: How do I prevent my new engine
> from rusting?

after run oil and if you dont need all the power drop to a lower nitro fuel

>> simple cure is to remove the varnish and that's best done by dropping the
>> piston and liner in a pan of boiling water with added biological washing
>> powder (NOT non bio coz you'd wate your time trying it).
>
> Washing powder for washing clothes?

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John Ferrell - 02 Oct 2008 19:07 GMT

>>Too lean and you've overheated the motor.
>>This still sounds too lean.
[quoted text clipped - 7 lines]
>How exactly does the engine get damaged from lean running? Is it
>excessive wear on the piston and cylinder?

During a lean run the lubricating properties of the oil are so poor
due to the heat that mechanical damage occurs.

>>One thing to check before
>>binning the motor though. Is it varnished inside?
[quoted text clipped - 15 lines]
>Bearings, piston and ring would cost about half of a new engine, so
>I'll simply get a new one.

Probably the safest thing for your Heli. If you have a low cost fixed
wing airplane that you don't mind a few dead stick landings you might
try a bearing alone. The rings and pistons sometimes look bad and work
fine. Be aware also that sometimes they look great and will not run
too!>

>Now, the big question is, of course: How do I prevent my new engine
>from rusting?

I feel that the rust usually originates from the mechanical failure.
The proper term for this is "fretting". Fretting can occur with parts
fully submerged in oil %100 of the time. The popular solution is after
run oil and there are as many believers as there are kinds of oil. My
personal picks are automatic transmission oil and Marvel Mystery Oil
for Air Tools. Whatever after run oil you use will make the engine
hard to start. I only use it when I store an engine.

>>simple cure is to remove the varnish and that's best done by dropping the
>>piston and liner in a pan of boiling water with added biological washing
>>powder (NOT non bio coz you'd wate your time trying it).
>
>Washing powder for washing clothes?

Be careful, some products eat aluminum!

John Ferrell W8CCW

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Beav - 03 Oct 2008 23:51 GMT

>>Too lean and you've overheated the motor.
>>This still sounds too lean.
>>Too lean.
>
> OK, but what about all the smoke and the occasional four-cycle? It
> seemed it was plenty rich, based on those signs.

That's only part of the story though. The times it isn't farting it's
definitely running lean.

>>You've probably f.cked the engine, but maybe you got lucky.
>
> How exactly does the engine get damaged from lean running? Is it
> excessive wear on the piston and cylinder?

Overheating causes the tolerances (piston/liner being the main ones) to
close up whch results in the cylinder liner pinching" the piston and
removing bits of metal When they get TOO tight, the piston is grabbed
properly and the engine stops dead. When it's happenin intermittently,
thepistin gets scored along with the liner and the deposits are scattered
throught the whole engine. This is then an ex engine.

>>One thing to check before
>>binning the motor though. Is it varnished inside?
>
> Well, I took it apart yesterday. The top of the piston is dark brown,
> otherwise, it's all nice and clean.

Not varnished up then.

> But I think I have found the problem: The rear (or is it lower on a
> heli?) bearing is completely shot. The races look terrible, and even
> the balls are visibly damaged. The piston and the ring have scratches
> that can easily be felt with a finger nail. The cylinder liner looks
> good, though. The glow plug has almost no coil left at all. Only short
> stumps left at each end.

Overheated to f.ck, metal removed from one part and distributed happily
over, under and into other parts.

> It seems the cause of the damage was rust. The bearing had clear signs
> of rust on the side of the races. The front (upper) bearing, though,
> was like new.

Methanol is hrdroscopic, in that it absorbs water from the atmosphere. This
can rust an engine pretty easily and the easiest way to ensure it doesn't
happen is to run the engine COMPLETELY dry after flying. Run the motor until
it stops from lack of fuel and then immdiately start it again (without
re-fuelling). It'll run, but only for a couple of secinds. Now there's no
fuel, so no methanol inside the engine.

The heat will evaporate ny residue inide the engine and it won't rust. Well
not unless you're in a really humid part of the world and iof you are, shoot
a little airline oil into the engine (through the plug hole) and spin the
motor over a few times.

> Bearings, piston and ring would cost about half of a new engine, so
> I'll simply get a new one.

Good thinking, but make sure you don't run it lean.

> Now, the big question is, of course: How do I prevent my new engine
> from rusting?

Ohh, I must read a whole post one day, before I start typing:-) So... see
above.

>>simple cure is to remove the varnish and that's best done by dropping the
>>piston and liner in a pan of boiling water with added biological washing
>>powder (NOT non bio coz you'd wate your time trying it).
>
> Washing powder for washing clothes?

Yep. Biological powder IS for clothes not dishwashers.

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Robert Roland - 05 Oct 2008 19:26 GMT

>> But I think I have found the problem: The rear (or is it lower on a
>> heli?) bearing is completely shot. The races look terrible, and even
[quoted text clipped - 5 lines]
>Overheated to f.ck, metal removed from one part and distributed happily
>over, under and into other parts.

I have tried googling a bit on the issue. It seems several other have
had bearing problems with this engine and a couple of other models
from OS. I'll keep an eye on the bearing on the new engine, and
replace it if I detect the slightest sign of damage. Do I get
stainless or ceramic next time?

>Methanol is hrdroscopic, in that it absorbs water from the atmosphere. This
>can rust an engine pretty easily and the easiest way to ensure it doesn't
>happen is to run the engine COMPLETELY dry after flying. Run the motor until
>it stops from lack of fuel and then immdiately start it again (without
>re-fuelling). It'll run, but only for a couple of secinds. Now there's no
>fuel, so no methanol inside the engine.

I have always done this, except for the few times when I have crashed
badly enough that it was not practical to start the engine.

>The heat will evaporate ny residue inide the engine and it won't rust. Well
>not unless you're in a really humid part of the world and iof you are, shoot
>a little airline oil into the engine (through the plug hole) and spin the
>motor over a few times.

I also fly in the winter, and my workshop is kept 10-15 degrees C
above freezing to keep tools and other stuff from rusting when the
temperature changes. It is theoretically possible this could cause
condensation, but only when the crank is stopped so that the intake
port is open.

I bought some after run oil with the new engine. A few drops through
the carburetor should hit the rear bearing very well.

>> Washing powder for washing clothes?
>
>Yep. Biological powder IS for clothes not dishwashers.

OK. There's no limit to what you can learn in this newsgroup :-)

Thanks for your comments.

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Beav - 21 Oct 2008 09:20 GMT

>>> But I think I have found the problem: The rear (or is it lower on a
>>> heli?) bearing is completely shot. The races look terrible, and even
[quoted text clipped - 11 lines]
> replace it if I detect the slightest sign of damage. Do I get
> stainless or ceramic next time?

No need for exotic materials if the fuel has sufficient oil of the right
type. That basically rules out some of the fuels on the market. Bekra fuel
is excellent for small two strokes though.

>>Methanol is hrdroscopic, in that it absorbs water from the atmosphere.
>>This
[quoted text clipped - 7 lines]
> I have always done this, except for the few times when I have crashed
> badly enough that it was not practical to start the engine.

Not that then :-)

>>The heat will evaporate ny residue inide the engine and it won't rust.
>>Well
[quoted text clipped - 8 lines]
> condensation, but only when the crank is stopped so that the intake
> port is open.

And your engine is perfectly airtight, which they aren't.

> I bought some after run oil with the new engine. A few drops through
> the carburetor should hit the rear bearing very well.

It won't. It'll pass right through the centre of the crank and exit just
behind the rear bearing completely missing the balls and races. To ensure it
reaches the moving parts of the bearing, the engine needs to be spun on a
starter to atomise the oil and move it around the primary compression
chamber.

>>> Washing powder for washing clothes?
>>
>>Yep. Biological powder IS for clothes not dishwashers.
>
> OK. There's no limit to what you can learn in this newsgroup :-)

It's good for getting fully coked up silencers free and clear again too.

> Thanks for your comments.

NP.

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Model Forum / Radio Controlled / Helicopters / October 2008

Engine problems