da Rock

Did I get your attention? Well, truth is, there is some truth to the TITLE.

I'm not into big gassers. But a buddy just took the plunge. ("plunge" is right, he "took a bath". Spending $1,500 for ONE model is taking a soaking in my opinion. But I digress.....) And he's been less than sure of himself about setting the needle on his 50cc engine. And I got no experience with gassers.

But what the problem is........... is:
The engine came "pre-tuned" from DA. And they told him that he shouldn't have to touch the needle setting. And the thing sounds really bad. Truth is, it pulls GREAT, but it can't even come close to qualifying as, "never misses a beat". And it hasn't quit once. Only way to get it to quit is to hit the kill switch, near as I can tell.

We recently had an IMAC contest at our club, and one thing I noticed during that weekend was that the majority of the engines sounded like the owners didn't have a clue on setting them. Now....... that's the opinion of someone who really has never been around the biggies before, and who has run 2cycle glow for 50+ years. And I didn't see but a couple of deadsticks the whole weekend. So I gotta think those engines are "too forgiving" from my point of view.

What's the deal with so many big gas engines sounding like they're an old Model T with a couple of broken plug wires?

I've got nobody I fly with that's got experience to tell me. So I'm asking here. tia

bubbagates

My Feedback: (32)

I have never seen a gas engine that came right from the manufacturer that did not need some fine tuning. Da engines are set to run where they are assembled so unless you live at the same altitude, you will need to tune it. Again the same goes with others.

Tuning a gas engine is fairly simple once you understand what you are listening for.

RCIgnitions has said many times and so have others that all engines can be set by following a few simple steps and I have used thee on any engine I have tuned for myself and others and it works well

Set both needles at 2 turns open

Using a tach, lean the high end until you get max rpm, then richen it to lose about 200rpm.

Now lean the low end until it will not transition to full throttle when the throttle is opened quickly. Now slowly, using small turns (like 1/16th or a tad more) until the engine transitions quickly and smoothly. Now check the high end again and adjust as needed to get the same results as before, go fly

Almost all electronically controlled engines will burble (have a four stroke sound) right in the mid range and also at low range. This improves as the engine breaks in but in some cases never goes completely away. The only one I have ever seen where the midrange was dead on was a Brison engine using mechanical ignition timing advance.

One also must rmember that most gas engines are not fully broken in until they see 10 gallons or more of fuel. A Da50 likes Lawnbo ashless at 32:1 for the first 5 gallons using a good 22X8 propbut not a wide blade so that the engine turns around 7200rpm, give or take 100 rpm. After 5 gallons switch it to 100:1 Amsoil Saber and change the prop to a good 23X8. If you now turn that prop around 6700 to 6800 then leave it alone, if it turns any slower go back to the 22X8 for another gallon or so.

It takes a bit of getting used to when you hear the engine burbling, because most people are used to hearing a nicely tuned, well broken in 2 or 4 stroke glow being smooth from idle to full. Gas engines get there but they take a bit longer. The nice thing is fuel consumption is really good but that also is a pain because a 50CC can take a long time to get to 10 gallons when you use 16 ounces at a time for 15 to 18 minute flights

da Rock

Thank you. That about covers it.

I just copied that and plugged it into an email to my flying buddy. I knew I'd get good advice here. Thanks

bubbagates

My Feedback: (32)

Cool,

I hope you corrected my many spelling errors in there. It pays to proof read before hitting OK but it's obvious I did not do that <shrug>

rodney tanner

Thanks for the info. I have just bought a used (5 gal approx) ZDZ 80 for my first gas IMAC project (WH Extra 260) and plan to use the Dick Hanson header-canister set up for the ZDZ 80. Being used to a smouth flawless transition I took for granted on my OS 140RX pattern planes, every gas powered plane I see at the club seems to burble in the transition. But, yes, these have been relatively new (bellow 10 gal) engines. My aim is to get the same smouth, quiet result we aim for on a pattern setup. So I will expect burbles till I get past 10 gallons:-)

amjflyer

To prove you wrong! I had a 215cc Mackay radial, thats a big 4T gas engine, it sounds awesome right through the range...

But in a sense I agree, i have always loathed two strokes and gas two strokes are even worse sounding but on a really nice set of cannisters or better still pipes they do sound awesome! Go listen to a DA150 on Greve pipes, it'll blow your socks off! The key seems to be if its 4 stroke anyh old silencer will do and it will sound great, on a two stroke just make it as quiet as possible and it will sound ok, or be drowned out by the much nicer sound of the prop roar.