Hi there,

Having a few problems with an old aircraft. Hasn't been used for about 10 years. Took a little while to fire up the engine for the first time again, and since then the aircraft has done two 10 minute flights.

Problem now is that the engine is not throttling up properly. It seems to work fine from 0-50% and anything above that it splutters and cuts out. I've played around with the high end mixture to both lean and rich sides and when it eventually does get a higher RPM, it works until i lift the nose into the air.

When the nose is lifted up, the engine RPM gets lower and lower then cuts out. If i hold the nose down the engine initially increases in RPM and then cuts out. The tubing in the tank (without opening) appears to be intact and the clunk is still attached to the tubing. The engine is an Irvine 25.

I've tried messing with both the low end and the high end needle to no avail. It's probably reached the stage, where all the settings are way out.

Any hints, tips, name calling, or pointing out of 'obvious' mistakes are welcome...........

Cheers.

Gareth.

Obvious and 'deleberate' mistakes of course..................ahem

From OPJOSE himself:


If you've run the engine, the first thing to check is that the muffler
pressure nipple is free from obstruction.

Inserting a very small hex key or something similiar will help dislodge
anything in it.

Make sure that you get good airflow if you blow into the nipple ( using
a piece of clean tubing of course! ).

As far as the carb seal, I usually put a clamp over the carb and
tighten the clamp down, before beginning to screw the carb's retainer nut. Be
careful not to overtighten it however, and a bit of loctite on the nut
helps.

I assume that the engine is new.

If so you'll find that it will not really settle in until it has had a
gallon run through it.

When you initially start the engine on any day, let it run for at least
a minute before you go to adjust or tune it.
This lets the head come up to temperature. On a new engine this is
particularly important as the engine will not be tuned properly if you
adjust it before the temp comes up.

Set the HS so that you can run the engine up to full throttle... but is
still rich or even four stroking.

Let it run for a few seconds this way, then start leaning it out while
listening to the engine.

As you lean it it will speed up and as you continue to turn you will
get to the point that the engine will appear to slow down again.

Once you reach this point, turn out the HS needle until it speeds up
again.

Now once at this point, back it out ( unscrew ) it another 1/4 turn.

Drop the throttle to idle.

Let the engine run at idle for 2-3 minutes.

Note if it slows down over time... but continues to run

If it does, it's too rich on the LS.

If it runs for a bit but then seems to cut out quickly, the LS may be
too lean.

Adjust in 1/8 turn increments until you get a constant idle speed.

You may want to open the idle setting on your TX a bit to let it
initially run with a slightly higher than normal idle. Once the engine is
fully broken in, it will sustain a lower idle speed much better.

Once you get a consistent idle, run the engine back up to full
throttle.

Check to see that the HS hasn't changed too much, but try NOT to adjust
it yet...

Now at full throttle perform a pinch test.

Pinch the line quickly. The engine should briefly increase in speed and
settle back to where it was.

If it cuts out, the HS is too lean. If it seems to have no effect, it
may be too rich.

Pinch the line off until the engine stops. Note how long it continues
to run this way.

If a second or two ( usually it will speed up then stop ) you have it
just about right.

If it runs longer, it is too rich.

If it stops almost immediately, it is too lean.

Adjust the HS until you get at least a second of runtime with the fuel
tubing going to the HS needle pinched off. ( Not the tubing between the
HS and LS needle of course... ).

Once you get this right, bring the engine back down to idle, and check
to see that it maintains a steady idle over time.

Don't worry about a LOW idle yet, worry about a STEADY idle instead.

If you are getting a steady idle, then PINCH off the fuel and hold it.

The engine SHOULD continue to run for 8-10 seconds or so, it should not
run past 10-15 seconds.

If the latter, it is still too rich on the LS, adjust until it will run
for about 8 seconds.

Once done, check the transition from low speed to high speed. Is it
somewhat smooth?

It may NOT be perfect, you want it a little rich on the ground as it
will lean out in flight.

But you do not want the plane stalling out because of too much fuel on
takeoff either...

Once you are at this point, perform a nose up test...

With about 1/2 a tank of fuel...

Hold the plane and bring it to WOT, then point the nose straight up.

The RPM's should increase

Too lean of course...but not that simple.

Try replacing the tank or seal the tank's cap with selicone.
That rubber piece on the tank's cap might had gotten dried and crack. 10 years...
You might be loosing presure , or not enough presure when the engine gose to higher rmp.

I'd replace all of the fuel line. If it has brass tubing. Corrosion build up might had set in on the inside of the brass tubing.
I 'd just get another tank..by the time i replace the brass tubing, fuel tubbing, buy selicon...it'll cost more.lol


other rubber pieces that'll effect your tunning.

The O ring on the carb's throat.
The O ring on the needle of needle valve.

I would had flushed and cleaned the engine before even starting it.

Great post by Yetti831 and also good info from fly x. When Gareth explained the original situation he mention that is a 10 year old engine which I think that was stored. In my opinion I would tear apart all the engine and specially the carb. On the engine I would look for corrosion (even that this is not the problem, it could be in a very near future), once the engine is cleaned up (Changing bearing could be a good choice here) I would replace all O rings and make sure that the carb is completely clean (10 years of stored castor oil would produce a lot of mess inside). Then assemble the engine again and run it in a test stand (If available) and start tuning the engine just as Yetti831 described, at the end you will have a great performer.
I have stored a number of engines for a while and I had to replace o rings and flush the carbs until they are completely clean, then they perform just like the last time that I use them. Now a days when I know that an engine will be stored then I take the glow plug off the engine, plug the carb, fill the engine with transmission oil and put a dummy plug, that simple procedure lets me sleep knowing that all my engines are well cared.