guys what is the cause of an engine that runs excellent and after a few mins of flight just stalls as you try to slow down,i have been around gas engines a long time and never had any problem tuning them,the high and low are set nice,yesterday for the first time i had two dead stick landings which could have ended bad...

the engine quit twice,i bought it in and richened the low a little,it didn't stall in flight next time but i wasn't as adventrous with the plane,it's a 3d 33cc plane, this is taking the confidence out of it a little,now my flights need to be very high up to make sure i can recover if it stops.

fitting the cowl on makes the engine run terrible,the plane is an inverza 33.. i opened the cowling under the carb more so i am hoping to see some gain.....

would an air leak cause this?? i checked tank and it is perfect,no leaks...

i did have a slight air leak on the back plate of the engine which i sealed up since but i am finding it very difficult to obtain a nice tickover which isn't draggy on the prop. here is what's also happening for me.


i rev engine flat out to check high speed needle it sounds great,i pull throttle back closed fully and it starts to tick over very Low almost dies,so i adjust throttle trim,but the longer i let it idle,the higher the revs start to climb,everytime i throttle back after full throttle bursts it almost wants to quit...... so i need a high idle set with TX to keep engine going,which is hell for landings........


any advice,i tried reading over thread but information overload.....

thanks
Dan

.see if it is getting hot. also, set a high idle up sounds like it is over heating to me.

johnber,

thanks for that,i had the cowl off for this flight,i tuned the high speed jet and low as good as i could,yes i also thought it might have been getting a little hot and maybe i had the low speed jet too lean but i'm not convinced....

it's going a little better with the back plate leak fixed but i'm not sure it's sorted,how can one land with a high idle?

i would like to know what reasons would cause it to quit after some high speed flying,i gradualy decreased the throttle after the high speed flying,it wasn't as if it stalled straight away which makes it stranger, it was after a slow speed circuit it quit then...

it's an evoloution 33cc using a 20x10 prop, the engine on the ground is superb only the tick over is weird and hard to adjust cause of the rpms starting to climb the longer it's left to idle...

also on the ground no hesitation but there seems to be in the air a throttle delay time.... even with cowl off.....

i'm baffeled

I'd check for more air leaks. Sounds like a crack opening after heated. Had a carb spacer do this to me last year. Just a thought.

mmm propsnwings...i think you are on the money,maybe it was the backplate so,would that effect it?
maybe my leak is still not sealed enough....

must test it and see....

you might be way lean on the low end which would account for the idle creeping up. Sometimes it's best to start the tune over from the factory needle settings after elimnating any other possible issues. Also, it's pretty easy to set up a two position switch on most radios with a high and low (landing) idle setting.

thanks 3ddave,

ok small update,i think i might be on the ball now,i took it out this evening and fitted the wings and badly needed to do some tuning,as a precaution i replumbed my fuel tank,and i previously sealed the leak with blue RTV on my back plate,i used lots of thread lock on the bolts,let it sit for 24hours as it says the blue RTV get's it's best bond in this timeframe...

anyway,i took it out and wow the engine ran a lot nicer,so i started with high speed,am i doing this right ??

tuned it until it would bog down,then richened it up until it ran good again,done the same with low speed needle,leaned it small incriments until it lagged and wouldn't rev up,then richened it to the sweet spot....

seems to be very nice and powerfull now on a 32:1 mix,i'm using a 20x10 prop (the reccomeded one is 18x8 i hope this prop won't be overkill for it...shouldn't be...

i think i was too rich on the low speed needle.


what you lads think?

only thing i see is any silcone sealer will not work well with gas.........over time it will eat it if the silicone is cured or not. use a cement such as yamabond, gadskacinch etc. again.....fergit about silicone! Now high idle set up on the radio is quite common for flying, set a reliable idle on the ground for low idle, set the high idle up a few hundred rpm for flying. keeps the fire going when twisting and turning.

thanks johnber,

your opinions taken onboard,i like the idea of having two idles on a switch,that's a great idea.

as for the blue RTV,i have used it for years in the rc car gas engines 1/5th scale in racing and my engine builder and tuners used use it also as a replacment for gaskets on the head to make even more power without the gasket height,and it's proven to be ok. so i'd say it's ok with gas.

you could be right though over time maybe it might need redoing...will have to see.

Originally Posted by grosbeak

Here's the revised diagram. Opinions welcome.

Originally Posted by grosbeak

You have done a wonderful job with your charting method.


KEEP UPDATING IF NECESSARY AND PUT THE FORMAT IN A TYPE THAT CAN BE EASILY PRINTED!!


Hope to meet you soon when I come to Ottawa in early July at your field.


How is Scott? I haven't heard from him on any of the forums for some time.

Originally Posted by bamdfisher

You have done a wonderful job with your charting method.


KEEP UPDATING IF NECESSARY AND PUT THE FORMAT IN A TYPE THAT CAN BE EASILY PRINTED!!


Hope to meet you soon when I come to Ottawa in early July at your field.


How is Scott? I haven't heard from him on any of the forums for some time.

Hi Brian,

Glad you like it - It's definitely a work in progress. When I tuned my never-run RCGF 32 this past weekend I started with the needles open 1.5 turns each. I had to bypass the section where you open the low needle just enough for smooth acceleration - After I tuned the high needle for peak RPM there was a delayed idle so I had to open the low needle just a smidge to correct that.

You coming down for the Stetson IMAC event? I worked the contest wrangling judges last year - what a job - but this year I'm determined to get in enough practice to compete. This will be my second competition so I'll be in Basic.

As for Scott, I see him at the monthly meetings but not much else. I know he's put aside his Ziroli DC-3 for now and is working on a P-47; pretty sure he is going to Joe Nall this year.

Look forward to meeting you this summer!

Originally Posted by FlightPunch34

thanks johnber,

your opinions taken onboard,i like the idea of having two idles on a switch,that's a great idea.

as for the blue RTV,i have used it for years in the rc car gas engines 1/5th scale in racing and my engine builder and tuners used use it also as a replacment for gaskets on the head to make even more power without the gasket height,and it's proven to be ok. so i'd say it's ok with gas.

you could be right though over time maybe it might need redoing...will have to see.

Blue RTV is definitely not ok with gas...

Originally Posted by goneflyin2002

Blue RTV is definitely not ok with gas...

What he said. It will possibly bite you when you least can afford it.

it makes no differnce because it's only on the backplate,this backplate still has a gasket,before any RTV was used engine was still running and running well,but not to it's fullest potential, (now fixed) only there was a small leak out the backplate,now that's stopped,so the worst case scenairo is it could leak again,as i say engine runs fine even with the small leak,i will just seal it up again if it leaks. the reason the engine quit in flight was cause i was wayyy too rich on the L jet.

P.S this stuff is blue gasket maker,i'm not sure if it's even RTV,i assumed they were all the same.i must check the name on it and report back.

Greetings experts!
I have a new to me, recently serviced 3W110iR2 inline engine that is doing a few funky things. It was set 1/4 turn rich by Aircraft Int. during service (approx. 1 1/4 out on highs, 1 out lows).
It was 4 cycling a LOT and not making good power. Running better at mid throttle and richer at full throttle. I leaned it carefully and repeated flight testing as it tends to richen in the air and not hold the settings from ground testing perfectly.
Here are the strange parts.
As the fuel tank empties in the plane, it runs better (sounds like it is leaning out).
As the plane is nosed down to gain airspeed for a maneuver it richens noticeably.
As the plane noses up it leans and sounds great.
ANY negative maneuver such as the roll at the top of an immelman causes the engine to basically die upon immediate negative (or lack of positive) g's. The top of a loop, while inverted in a roll...
I have re plumbed the tank and am positive the clunk is working normally. The vent is open and not restricted.
It has two independent ignition systems so a bad connection or whatever would have to affect both circuits.

I checked the needles after the last flight and found them almost to spec but a tick rich yet on the rear carb, a tic lean on the front carb.
I am going to route the vent from the carb base to inside the plane but beyond that think I have carb issues beyond tuning.
Thoughts?
Thanks
Windecker