help/suggestions on inconsistently running OS32?

[Greg Johnson]

I have a Shuttle and an OS 32 in it. My engine is showing the following
problem: it will run along fine for a few minutes, and then it will start
to temporarily lose fuel flow (or so it seems to me). For a second or so,
the exhaust smoke will completely disappear. Then it will come right back.
Or, the engine will thin out and rev up quite a bit and then settle back
down. Or, it will loose power temporarily and start to settle.

I've tried everything I can think of:

- checked all fuel lines and fuel filter
- disassembled gas tank and checked clunk
- disassembled carburetor and checked that it was clean and free
- looked to make sure that the throttle servo and arm are secure
- have used my (fantastic!) on-board engine temperature gauge to
make sure I have the mixture in a reasonable range. (This is
a fairly new product; sells for about $30.00 and is a HUGE winner.
I'd recommend it to everyone. A wire wraps around your cylinder
head into one of the heat dissipation grooves, and gives you a
real-time read-out of head temperature, plus maximum observed
temperature for the flight. I forget the name of the product;
Viper or Venom or some such.)

Anyway - I'm at wits' end - any thoughts or suggestions for other things
to check??

Thanks very much mates! (That was an attempt to be pseudo-British! ;-)
seems the Brits are the dominant presence on rhmc these days. Love to
visit you guys one of these days.)

Thanks in advance,

Greg Johnson

To quote a US State Dept guy: "Never thought I'd live to see the day when
a socialist is my biggest hero!" I thank Tony Blair SO MUCH for his stalwart
and brave leadership in the face of huge opposition. Agree of disagree with
his position, I think it can be truly said that we are witnessing a public
display of a leader forsaking political calculation and caution, showing
great personal integrity, and doing what he thinks is right. This is an
honorable man.

[Markerbeacon]

Greg, are you running a header tank? If not, you might give that a try.

-Mark


"Greg Johnson" <gregflies1@yahoo.com> wrote in message
news:8faa960.0303231834.5fc58d58@posting.google.co m...
> I have a Shuttle and an OS 32 in it. My engine is showing the following
> problem: it will run along fine for a few minutes, and then it will start
> to temporarily lose fuel flow (or so it seems to me). For a second or so,
> the exhaust smoke will completely disappear. Then it will come right
back.
> Or, the engine will thin out and rev up quite a bit and then settle back
> down. Or, it will loose power temporarily and start to settle.
>
> I've tried everything I can think of:
>
> - checked all fuel lines and fuel filter
> - disassembled gas tank and checked clunk
> - disassembled carburetor and checked that it was clean and free
> - looked to make sure that the throttle servo and arm are secure
> - have used my (fantastic!) on-board engine temperature gauge to
> make sure I have the mixture in a reasonable range. (This is
> a fairly new product; sells for about $30.00 and is a HUGE winner.
> I'd recommend it to everyone. A wire wraps around your cylinder
> head into one of the heat dissipation grooves, and gives you a
> real-time read-out of head temperature, plus maximum observed
> temperature for the flight. I forget the name of the product;
> Viper or Venom or some such.)
>
> Anyway - I'm at wits' end - any thoughts or suggestions for other things
> to check??
>
> Thanks very much mates! (That was an attempt to be pseudo-British! ;-)
> seems the Brits are the dominant presence on rhmc these days. Love to
> visit you guys one of these days.)
>
> Thanks in advance,
>
> Greg Johnson
>
> To quote a US State Dept guy: "Never thought I'd live to see the day when
> a socialist is my biggest hero!" I thank Tony Blair SO MUCH for his
stalwart
> and brave leadership in the face of huge opposition. Agree of disagree
with
> his position, I think it can be truly said that we are witnessing a public
> display of a leader forsaking political calculation and caution, showing
> great personal integrity, and doing what he thinks is right. This is an
> honorable man.

[Mike]

A couple of things come to mind....

Are you positive the fuel line from exhaust to tank is clear of obstruction,
and has no splits. Does the silencer have a good airtight seal all round?
Sounds like it could be a pressure problem.

Clunk tubing can sometimes look okay, even if it has actually turned a bit
jelly-like. Bits of disintegrating clunk tube in the fuel won't help.

You have obviously tried new glow plugs..just because the plug glows in your
hand doesn't mean it will work in the engine.

Are you running the head speed too high or too low... you may have a cooling
problem, disguised by your gadget.

Are you using old fuel?

Does the exhaust run close to the throttle servo? I have had a situation where
the heat of the silencer was influencing the control of the throttle (in a
scale body I have to say). A piece of aluminium foil wrapped round strong
cardboard and put between silencer and throttle servo did it for me.

Or maybe the engine is just knackered!

Good luck, and of course we will all be interested to hear when you have
tracked down the problem.