DLE55 Dying

No, I have not changed the unit. (It was the Extra GP38 that we changed the unit)   Engine was running fine until sometime last November when Jon went to use it. Died after a few circuits, felt like fuel starvation. Naturally stripped carb and tried again. Did it again but appeared okay on the ground. Stripped it out again and had to wait 2 weeks for re-kits (royal mail strikes). Christmas week rebuilt it again. Been waiting for fair weather and well here we are, anything above half throttle cuts out.  I had thought about changing the ignition unit, maybe it is not advancing enough or just giving up as rpm rises. I will see if I have spare until somewhere and try it.

Well its either lack of sparks or lack of fuel - The latter could be one of a dozen faults but the former is one these 
Plug
ignition unit 
crank sensor / wiring
Ignition switch 
battery 
I agree you need to eliminate these

HAVE YOU ACCESS TO THE RCEXEL TESTER - i have one 

Hi Kevin,
No I do not have a tester. If it stays dry today, I will temporarily plug in a spare ign unit (ex Dave Bright) and see what happens. I have also found a spare carb (also ex Dave) that I will re-kit as a stand by.  If they don't work I can always blame Dave, albiet he gave them to me when I bought his DLE55 back in 2013. 

Have you been using E10 petrol? If so, perhaps it has affected the characteristics of the carburettor's diaphragm in some way. You seem to get the problem in the air, starting is OK though. Could it be that the tank vent  has become partly obstructed? I remember reading about a two stroke petrol that kept failing. The reason turned out to be faulty roller bearings in the con rod. They were crumbling and the fine metallic particles were causing the spark plug to short out. I had a problem with my two stroke powered leaf blower, starting was good, but failed to run. The cause in that case was a delaminated fuel tube, a sort of woven Kevlar thing with an inner and an outer, the detached inner collapsed shortly after the engine was started, took me ages to find the fault.
 

Well today I got it started again, easy. Whilst trying to pull the plug lead off I managed to pull the whole panel off the firewall.  Now I am really p**sed off.  So, three hours later I have re-secured the panel and made it detachable (fixing screws rather than glue) so now it is easier to access the ign module without having to pull all the tank out again to gain access, assuming I "might " have to swap the IGN unit at a later date.
Anyways, engine running again but dies at the transition point where the main jet comes in with low jets, ie; about 2/3rds throttle.  So, I may pop over to Kevin's for his RCEXel tester to eliminate the possibility of it not coping with high rpm. If that says all is well then it is back to the carb again.

Brian, fuel lines have been replaced.

Found this on Canadian RC forum.  Now I just wonder if..... because this is exactly my issues
If the engine starts a runs for awhile, even a couple flights, and the problem returns, then you've got "DLE sealant" in the hi/low passages.

"John said he had this with a couple DLE carbs. I started watching Walbro service videos. One video made/produced by walbro talked about the old walbro practice of sealing the welch plugs with nail polish being abandoned. They no longer recommend sealing the welch plugs. The ethanol in modern fuel attacked the sealants and the crap (inside the screens) gets into the passages and blocks at the needles.

I couldn't flush this stuff out after many attempts. This happened on two DLE61s in my case.

At the suggestion of a friend, i used brake cleaner on all the passages of the carb block after removing everything, covers, gaskets and needles.  I shoot the cleaner thru every opening till is ejected out the a mating exit, 3 times over a day. After the last, i blew it out with air (note walbro warns against hi pressure).

I reassembled at the original needle settings and all the engines ran mint since and have never acted up again.

If you do some searches, you see DLE still uses sealant on their carbs in contrast to walbro. A new walbro carb will work great. But i think about 90% of the DLE carb issues are probably solvable with a $2 dose of brake cleaner!  Its a simple and repeatable test. And a simple solution if the engine runs normally after the test, but the reoccurs with a couple flights."
 

As planned took the carb over Kevins. Stripped completely out.  Comparing it other similar Walbro carbs it appears that this one, a DLE has extra jet. Anyway we found corrosion on the jets, odd as I cleaned them not long ago.  I decided that the carb is scrap and I had spare Walbro (ex, Dave that I had re-kitted but was short of a fuel screen so I used the one out of the scrapper.  Thought it would be straight swap but no. I have had to re-configure the throttle lever and control rod which also entailed drilling a new hole in the firewall.  Today, Wednesday I've got a bit more to do and then get it started hopefully later today - watch this space.

We could not test the Ignition as Kevin had a tidy up recently and could not remember where he put it.  Late yesterday it turned up - Murphy's Law!

After also having to make up a new choke rod it was time to fire it up. after quite a few flips to pull up fuel it started and runs.  Full throttle seems okay now but unable to tune it properly at home.  Idle is nice too.
I took this opportunity to reset the throttle linkage mechanism as there seemed to be of a bit of "dead area". In other words the servo movement did not accurately correspond with the throttle arm movement.

Now I can get on with checking over my other models ready for the Spring.

A short while ago during all these carb problems I went over to Kevins and we stripped the carb right out. 
The jets appeared to have corrosion/rust on them.  Only a little time ago I had these out and they were fine.  Blame E10.

Today after a carb rebuild on the CAP 232 a few months ago and waiting on fine tuning, I thought I might just take it outside on my grass and get it running.  Fire up, run a split second and backfire die.  Not back to fuel starvation again/blocked jets?  Anyway after checking the carb in situ I thought I might as well check the plug.  Corroded and the oily rust had virtually short circuited the electrodes.  Water in fuel    Ruddy E10.  Be glad when the last of it used up in the mower.  Gotta be VPower or BP Supreme next time round,

I always use Stihl Ultra 2-stroke oil as it has lots of additives for corrosion resistance and anti-coking. It is very expensive at £20/liter but my pistons always look like new with no gum down the sides and my bearings seem to last well too. I also use a shot of Redex in the fuel every so often and my carbs seem to appreciate it.

I may also change my oil brand later. Funny you mentioned about Redex because I was thinking the same thing.  I have nearly used up all my E10 and have "splashed out" on Shell VPower 99 (it is relatively cheap again now). It might not need it but maybe 10 ml of Redex in 4.5 ltrs might help too avoid this gunge stuff from BioFuel.

Recently GWR diesels have been breaking down since they started using a higher ratio of Biodiesel,  Clogging up the fuel filters and those filter are BIG.