[Sandy]

when I replumbed the tank i checked the clunk - not sintered bronze (I had that thought one night about 3AM)

[aceplant00]

Are you able to run the engine with the throttle servo not powered. You will be able to slowly throttle up and see if it dies out at half. I am heading towards a radio progam issue

[Eye Can Fly]

I remember now how I corrupted my Tx program for one plane, I re-organized the plane menu. I don't know why it did it but it did.

[Sandy]

yup, can give that a try.....I did sit down with the Tx last night and went through the whole set... since I'm a simple flier there's not much programmed - to keep down lines straight I have -5 elevator at idle, nothing else....

[jsparky]

I had a problem with a gasser here a while back with alot and I mean alot of air in the lines.. to the point the engine did not run very well would not reach full rpm and would stubble.. having changed all the " new " fuel lines for more new lines.. checking every possible entry point for air.. I finally gave up.. called a friend of mine , a long time modeller and asked him.. he said two words.. and the light suddenly went on being a mechanic.. I understood what he said..

Oxygenated fuel..

In order to get our cars to run more powerfull and cleaner... the companies oxygenate the fuel... much like an air bubbler in a fish tank.. The clunk in the tank was vibrating at a frequency that was causing the air to seperate from the fuel.. this air would get sucked up the fuel line and where ever there was a high spot in the fuel line.. the air got trapped there... once the engine shut down the fuel gravity feed back to tank leaving no trace of what had happened.. it was not untill I had pulled the cowling off and bench ran the plane did I see what was going on..

Ok .. so now you say the plane has been fine for several years ,, why now?? comes back to the airframe.. there must be some kind of change in the airframe I would think.. that has changed the harmonic frequency of the airframe and causing the clunk to vibrate more or at a different frequency..

Sound a bit out of touch with reality.. probably except that a buddy of mine had an ugly stick.. flew for a year no problems.. very nice model to fly.. this year he made changes to the wing and changed up to a bigger motor.. after a half dozen flights.. he drove it into the ground out of control.. the post mortem showed every glue joint on every !!! hinge had let go.. the old ones from the previous year and including the new ones this year.. causing an aileron to depart in flight.. only explanation was harmonic frequency.. same as making buildings earth quake proof by building them to resonate at a different frequency than the earth quake..

Now this sh*t is real... a bit far fetched... but it is there..

If you can't explain the reasonable.. start looking for the unreasonable..

BTW... if I have not bored you to death by now.. the fix for the air.. I bought the eveloution fiber filter clunk for their gassers..

[Lorne @ Pro-RC.ca]

If it is not the engine eliminate the other possibilities by doing the following
ONE AT A TIME
1) run the throttle servo by hand to make sure it is not a servo thing. (make sure your servo does not open your throttle past wide open by looking down the throat of the carb. Once you go past wide open the engine will loose rpm and die)

2) A123 or life battery direct to the ignition, no switches

3) New fuel. I suggest shell premium

4) Plumb in a temporary fuel tank by sitting a tank in the model and plumbing a direct line to the carb.

5) make sure the choke spring is not off closing the choke on the carb as the throttle advances

[Sandy]

Oxygenated fuel - absolutely no bubbles in the line - i can see the entire line while standing behind and trying the *@!>}$% thing each time....but am going to get a fiber filter

throttle only opens to full - I can see inside and the is a mechanical stop; I can see the servo (and the choke servo) and neither move

have tried a direct A123 to the ignition

fuel is new

still to try a remote tank

[itizme]

what happened when you neutralized the pressure over the diaphragm?

[Lorne @ Pro-RC.ca]

Originally Posted by Sandy

Oxygenated fuel - absolutely no bubbles in the line - i can see the entire line while standing behind and trying the *@!>}$% thing each time....but am going to get a fiber filter

throttle only opens to full - I can see inside and the is a mechanical stop; I can see the servo (and the choke servo) and neither move

have tried a direct A123 to the ignition

fuel is new

still to try a remote tank

what kind of fuel. I got fuel once that for some reason made a da 120 and da 170 dead stick. after fighting with the needles I decided to try fuel from a different gas station. Both engines worked like a charm. Never did know what was wrong with the fuel but the chain saw did not like it either

[Sandy]

Originally Posted by itizme

what happened when you neutralized the pressure over the diaphragm?

no change