zope_pope

Hi all,

I want some opinions on possible problems and what to check for. I have almost finished running the 2 gallons of penzoil two stroke oil (petroleum based) at 32:1 through the engine, but the last 6 or so flights, the engine has been extremely hard to start and the idle has been very unreliable. It likes to quit in inverted spins. This is my first gasser, and even at factory needles it is not running great at all. I have leaned it out very slowly (1/16" turn at a time) and have great transition, but anything under 2000 rpm is just unreliable in flight.

Anything you guys think I should take a look at, or any similar experiences? Thanks!

Tired Old Man

My Feedback: (1)

You said two things that gave it away, first gasser and factory settings. The first item is not a bad thing, but beliving there is such a thing as factory settings is not.

ANY new engine IS NOT set to run correctly at the factory. At best, it has been set only well enough to start. From that point on each and every engine has to have the needles adjusted to suit the climate and atmospheric conditions it will be running at, along with the size and type of prop that will be used on it. Both have an effect on the engine tuning.

Take a few moments to read the plethora of articles in this forum that have been written about engine tuning and I'm certain all your engine woes will dissapear.

Steve

My Feedback: (54)

Also check your carb bolts. Sounds like you may have an air leak. I don't think the factory torque is enough. I usually get almost a full turn on my gassers when they are new. They need to be checked after a couple flights also. The gaskets can be sealed also. I try and check every thing on a new motor before I install it.

bhanley

The above are good suggestions but in addition I found with the couple that
I have had that they really don't get happy until you put about 5 gallons
through them.

JoeAirPort

My Feedback: (41)

Bump up the idle a few clicks before taking off. Bump it back down for landing. Use the idle down feature to reduce landing RPM's if you have it on your tx. Also a leaner low end will take a few more flips but I never minded it. If you are talking about flip after flip and no start, it may need a little prime from the choke before starting.

zope_pope

I understand factory settings aren't what I should run it on, but I have tuned the engine so that it runs the top end rpm and backed it off a few hundred. I have also leaned the low end till it tries to die when the throttle is advanced and then richened it off, but it just doesn't want to fire within (literally) the first 50 flips. I'd love to cover the carb with a finger and prime, but the engine is very much in a cowl. Also, I cant get it to fire even while choking. I read an article in Model Aviation yesterday that recommends filling the whole in the choke plate. Good idea, bad idea? I think it would make a lot better seal and easier to prime the engine. Thanks so far for the advice, I'll pull the engine afterwork and do some inspecting and post the results.

JoeAirPort

My Feedback: (41)

One thing to check: does the choke plate seat fully? Some people have found that it doesn’t for a couple of reasons. One is that the plate will simply not close due to the plate not being assembled properly from Walbro. The other is that the choke servo is not setup properly so that it does not seat.

It could also be an electrical problem but there is an easy way to see if you are not drawing fuel. Take the cowlng off if necessary and get full view of the fuel supply line to the carb. When you first prime the engine does the fuel climb up the line nice and fast like it's supposed to? Mine goes like an inch or two each flip. It gets up to the carb very fast. If yours does not it's either a choke problem or the pump in the carb is not working right. Is the pressure pulse line sealed? No leaks? Make sure it's getting healthy pressure pulses form the crank case. Are there any air leaks in the fuel supply line or tank fittings?

bubbagates

My Feedback: (32)

Soldering the choke hole does work but all you are doing is fixing a symptom. All of the above suggestions are pretty good.

Here are some other things to look for.

When it is cold and you fill the tank and close the choke, open the throttle just a crack and try rotating, not flipping, the prop in the normal direction and see if the fue is moving on each rotation. If not you have A) an air leak, B) the choke is not fully closed, C) the pump diaphram in the carb is leaking. The fuel should move a good inch or more

If that all works then try priming the engine by squirting fuel into the carb. Close the choke, rotate the prop a few times to get the fuel inoth the cylinder, turn on the ignition and see if it starts. Be careful when priming it as to not flood it to bad. If you do get too much in do not choke it

If all of the above suggestion by everyone else and myselfdo not work, call DA, you may have an ignition problem

zope_pope

Well Starting issue. That has been solved.

I pulled the cowling off, supervised the fuel flow and it wasn't flowing when i choked it like normal. Upon further inspection, the way I have zipties holding the manual choke, it was pulling the choke open quite a bit. Took the zip ties off, choked it fully, flip the prop 5 times, and pop. Just like it used to. Adjusted the manual setup, and I think I have solved that issue.

Now onto idle. Is it just because the engine is still new? I was hoping to get atleast a 1800 rpm idle.

ljones5000

My Feedback: (2)

While I don't understand how you used zip-ties on the choke, maybe the same problem holding idle while landing. Perhaps the choke was not fully open causing the engine to die while landing.

Have you flown since fixing the choke problem?

Larry

bubbagates

My Feedback: (32)

The idle will get better as the engine breaks in. Mine was like yours at first. Now after 15+ gallons it purrs at 1600rpm. It got loads better around 5 gallons. You also may be a bit too lean on the low end. On a DA50, you want to hear it burbling just a tiny bit up to the transition.

Tired Old Man

My Feedback: (1)

I just noticed the location of the problem engine. Just how cold is it there? Warming the engine up before starting it will probably make a lot of the problems go away. If it's below about 45f, then the temperatures will have a lot of impact. Try using a heat gun to warm the engine up to about 60 or so and see what happens.

bubbagates

My Feedback: (32)

Silver,

Good point. I never gave that a thought. I noticed 2 weeks ago when I was flying in 40 degree weather, the engine started like it always did but until it got heat into it, forget anything resembling a decent transition let alone a decent idle. You could easily hear when it was ready as the idle smoothed right out and the next blip of the throttle it transitioned like it always did

Zeeb

My Feedback: (41)

Yeah the ambient temps can have an effect on things...

I'm still pretty new to gassers but I've found that my ZDZ-50 doesn't want to play nicely unless it's warmed up a bit before trying to fly when the outside air temperatures get into the forties. Mine is just like bubba mentioned, I let it warm up a bit at what I'd call a high idle RPM after starting, and you can hear it smooth out when it's ready to go.

Still, IIRC there have been posts about the DA's quitting in flight on those spins he's talking about?

So there may be problems somewhere else as he's indicated that his needles are set in very much the same manner as I see others suggest, and it's the way I do it except that I do not richen the low speed needle anymore than is necessary to cover the transition. I'm not a DA owner, but it seems to me that it ought to idle reliably a bunch slower than 2000 RPM? My engine will idle between 1200 and 1300 RPM quite happily when it's warmed up, but I usually fly with it set about 1400 RPM.

zope_pope

Well I thought that it may be a cold engine problem as well (the first time it dead sticked it was in the 40's), but it was about 5 minutes into the flight. Also, doesn't the idle get higher as the engine temp goes up? Recently it has been very cold in CO, so this weekend I'll see if the engine is even less cooperative, however it was about 70 degrees when i last flew it and it still deadsticked once. It isn't overheating as I have the high end rich from peak. I have tried richening the low end a tad, but that seems to make the deadsticking more often. It doesn't feel to rich as any leaner it will try to die as I advance the throttle.

Maybe I should just set it to 2000, use the idle down feature on my radio, and see what happens. The deadsticking has only happened when tuned for about 1900.

Also, I am not sure if you guys need to know, but its running a menz 22x8, and i have the needles (best settings so far) at 1.5 high and 1.5 low.

Zeeb

My Feedback: (41)

It sounds to me like you're setting needles appropriately, fatten the top a little from peak and the low end just rich enough to cover the transition.

So... IMHO it's time to look into other possible problems like an air leak somewhere in the fuel system? Especially if things had been fine until recently, that suggests maybe something has come loose, cracked, etc. Have you checked all your fuel line connections? Carb still bolted on tight? Could even be somewhere in the case, if it's sucking air somewhere you'll definitely have problems getting it to run right.

As I said, I don't own a DA but I think it ought to be able to idle down more than what you're seeing.

There are a bunch of guys here with much more experience than I who have already responded, maybe they'll chime in again with this additional information from you.

bubbagates

My Feedback: (32)

What's the plug look like. It should be a darkish tan color. If it's lighter than that you are too lean, if it's darker then too rich.

I'd also look at the location of the ignition box. Make sure it's not in line with the muffler. After 5 minutes you could be overheating the box to the point it does not like to run correctly and you'll get a deadstick.

Also verify all fuel components including the carb pump and pop-off diaphrams.

You could also fly without the cowl on and see what happens

kmw1

Since I just bought a DA-50 as my first gasser and havn't even ran it yet so I'm not sure if this a good suggestion, but since it wasn't mentioned already did you bother to check the plug gap? The manuel states it should be 0.018"~0.020".....I'm going to check mine.

zope_pope

Hey Guys,

Bad day at the field. Engine starts okay, but first flight I had to deadstick on a downline. No big deal, plenty of altitude and speed. I took the canopy off and started looking at the clunk, because the engine quit under power on the downline. I added some weight to the clunk and then went up for another flight. Downlines flew fine, spins, fine, get low, and celebrate with a knife edge. From middle stick to full stick it increases rpms, then starts sputtering and dies. Not much altitude, so I went for the best landing site I could find. Unfortunately it took the gear off the airplane (fortunately nothing else is damaged. About 1-2 hours repair). I am getting desperate though, and am hesitant to take the airplane up flying again (ugh..).

I checked the plug color. It is sort of a copper color, i wouldn't say dark tan, but just plain tan.

I just don't get it. The idle was great today, I had to richen up the low end a tad (20 degrees today), but it would idle all day for no problem. It seems like it has to be with fuel delivery then. Right as I rolled to the knife, it started sputtering. Rolling level didn't help any. I've pulled the engine, and am thinking about sending it in just for piece of mind, but I don't think its the engine so much anymore.

Any thoughts? Thanks guys. (I'd call DA, but I get to work before they do, and leave after they do).

zope_pope

Also, thinking about replaing the hard tygon (included with the arf) with flex tube in the tank. Any thoughts?

Also, what about a different shape tank? This one is long and skinny.

huey-pilot

My Feedback: (17)

This sounds like the problems that I was having with my ZDZ 50, after a lot of frustration I changed the throttle servo and the problems went away. The old servo had problems centering properly with the engine running and the associated vibrabion. The new servo is a digital and has not given me any problems.

zope_pope

Well I installed a header tank to make sure I am getting fuel at all times.

Anyone know of a gas compatible bladder tank? That would be awesome. I also contacted DA, and they said it sounds like its lean, so I am going to go back to stock needles and see what it does flying on that (it will be pretty rich). If all is well, I'll tune again with the revised DA instructions (what they told me was completely different than waht the instruction manual said), and go from there. I'll keep you guys posted.

Josey Wales

My Feedback: (61)

What did they say that was different from the manual ?

zope_pope

I quote,

"The best way to tune the motor is to set the low end first. The way to tune the lower end is to go lean with the motor until the motor won't transition from low to high. For instance when you throttle up the engine either quits or sags out and dies. Richen the motor about an eighth of a turn. That should cure the sagging and quitting. If it doesn't cure it all the way only tune the motor a blade width at a time. As for the high end it is much easier to tune. Tune the motor until it achieves maximum RPM and HOLDS the RPM. A lot of guys try to achieve high RPM and backs it off 100 RPM they never check that it maintains RPMS. Once you get the highest RPM the motor will maintain then you richen the mixture so it loses about 100 RPM. The motor should run perfect with that procedure."

Essentially tune the low before the high. In the instructions it says to do it the other way around.

Josey Wales

My Feedback: (61)

Thanks..thats the exact way Ive always done it on both of my 50's..good thing I didnt read that part of the manual[8D]