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don't forget echo! - 6/6/2003 12:56 AM   
av8tor1977



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Status: offline 		Say Adam - "Avneat",

In doing some research, most of the 25cc and under engines seem to use the 7.94 mm carb. That would be a 15% increase from what I have, and would probably work well. The exception is the G-23 carb at 11 mm that a lot of people use for more power, but I think that would be too big for 16cc at 7000 rpm or so.

Do you know if these carbs tend to have the same mounting hole distances?? Mine are 1.220, (31 mm), center to center, give or take a few thou.

Thanks,
AV8TOR

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don't forget echo! - 6/6/2003 1:17 AM   
ANeat



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Status: offline 		Hi Bob; The hole spacing is the same; You should be able to swap any of them. The carb on my 16cc is also a W138 with the small venturi. Ive got a couple of the 22cc Echos, Ill have to see what size there running on them (tomorrow)
Adam

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don't forget echo! - 6/6/2003 1:41 AM   
av8tor1977



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Status: offline 		Ok Adam,

If you find that you have a 7.94 mm carb with that carb bolt spacing, and want to sell it kind of cheap.... I'll take it!!

Thanks,
AV8TOR
(Bob)

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don't forget echo! - 6/6/2003 2:08 AM   
ZAGNUT



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From: tel-aviv, ISRAEL
Status: offline 		hi all,
all my little 21.2 echos came with 8.5mm zama carbs and i haven't tried anything else yet. i have a stihl 009 saw (36cc) with an 11mm zama that i want to try on the echo, since it has an accelerator pump it should have a good transition even if it's too big. when i have time

av8tor, sounds nice and light! i wouldn't bother with the muffler-just make a short header to divert the exhaust. these engines don't have the high pitch scream of glo engines, just a mellow bark (to my ears). don't know what the noise limits are at your beach but try it. on my echos there isn't any difference between open exhaust and the muffler with the restrictive outlet removed.

dave

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don't forget echo! - 6/6/2003 3:18 AM   
Volfy



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Status: offline 		Wow Dave,you must have a better tolerance for noise than I do. I can't get close to these little engines when they are running without my earmuffs on. The muffs are on every time I fire up a model engine on the test stand - even dinky .25 glow engines. Years of playing with car audio and motorcycles have caused enough hearing damage that I don't care to loose any more. AFAIK, I'm the only homeowner around that put on earmuffs while weeding and mowing.

Anyway, all the WA and WT Walbro carbs (also the Zama knockoffs) share the same mounting dimensions - 31mm C-C. They are all meant for small engine below 50cc. You can put just about any of them on. You either give up top end power or Low/mid RPM transition. Each venturi size corresponds to an ideal range of flow rate, where it develops the optimum volumetric efficiency. Too small and the engine run out of breath on top; too big and the venturi doesn't develop good velocity to draw and meter fuel well at the low end.

I would guess anywhere between 8-11mm would be good for your 16cc, depending on whether you want absolute top end power or good transition.

< Message edited by Volfy-RCU -- Jun 5 2003 8:47PM >

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don't forget echo! - 6/6/2003 4:43 AM   
av8tor1977



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Status: offline 		Hey, thanks for the input guys.

On the exhaust, I thought of that. It would be ok as I like the throaty sound (noise) and I almost never fly at public places/fields. I've come up with a fairly slick idea for a free flowing muffler though. If it works out, I'll share it will all of you.

RE the carb. I didn't do the math on the carb, as I don't know what they will flow in cfm, but you are exactly right in what you say. We have a little formula we use for race cars and hot rods to determine carb size, though it always errs a bit low. On carbs, they always say a touch too small is better than a touch too big. Uh, don't think I should have said that!!!! Remember we are talking about CARBS here!

Tee hee, in getting back to business, I think the 7.92 mm carb which is 15% bigger than stock will be perfect for me. I'll share test results when I get them done.

Take care,
AV8TOR

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don't forget echo! - 6/6/2003 5:25 AM   
ANeat



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Status: offline 		Bob I sent you a PM on the carb, Also if you want a header made up I could do that to
Adam

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don't forget echo! - 6/6/2003 5:41 AM   
av8tor1977



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Status: offline 		Adam,

Sent you an e-mail. Also checked out your gallery. VERY nice work. You are a craftsman! I'll let you know on a pipe/muffler.

Thanks again,

AV8TOR

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don't forget echo! - 6/6/2003 5:50 AM   
Flypaper 2



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Status: offline 		When the weedwackers run out or break the string, they can over-rev with no load on them, so they put an undersize carb on to restrict the rpm. so don't hesitate to play with bigger carbs.

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don't forget echo! - 6/6/2003 6:09 AM   
Volfy



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Status: offline 		Actually, I thought the reason for the smaller carbs was that good throttle response and mid-range torque are the principle requirements for weedie operation. Wacking weeds needs a lot of trigger action and rpm control, and a smaller carb does a much better job. Very rarely do you wack weeds with the throttle wide open.

Chainsaw and blowers, OTOH, spend much of their service life fixed at full throttle, and top end power is the name of the game. Thus the reason for them being equipped with larger bore carbs.

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ACTUALLY... - 6/6/2003 6:17 AM   
av8tor1977



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Status: offline 		I'm rather sure you are both right!

AV8TOR

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engines - 6/6/2003 7:51 AM   
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Status: offline 		That weed wacker engine with a prop on it is most likley going to have a lot more load on it than just a string...thus you want to place the right carb to match the load. It will take a little experimenting. Used carbs are easy to come by at repair shops. Yard sales is a great place to buy about anything with a small engine on it...cheap!!!!Happy Hunting Capt,n

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But here in Mexico? :) - 6/6/2003 8:09 AM   
av8tor1977



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Status: offline 		Right you are Captain John, but it's a little tough here in Mexico. And I'm in northern Mexico; all sand. They think a weedeater is a "cabron" (Old goat).

Thanks!
AV8TOR

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IT'S RUNNING... - 6/10/2003 12:24 PM   
av8tor1977



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Status: offline 		Hi guys,

Got my little 16cc Kioritz running today. With no modifications to the engine itself other than my "JATO TUBE" propane refill can muffler and the CH ignition, it turns an APC 15x8 prop at 7000. That was just what I was hoping for!! I've got a bigger carb coming for it, (check's in the mail ADAM), so we'll see what that will do.

I'm really happy with it. Starts on the first flip and runs really nice with little vibration. It seems pretty light, but I can't post a weight at this time because the digital scales I just bought doesn't work. (Same with the damn Glo Bee tach I just bought, dammit!)

More as it a happens,
Thanks,
AV8TOR

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don't forget echo! - 6/10/2003 12:35 PM   
ANeat



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Status: offline 		Its running!!!, Thats great, Im glad to hear it performs that well. I hope the bigger carb helps, Its on the way I may have to convert the 16 cc I have now :

How did the muffler do?? Quiet or Loud ??
Adam

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don't forget echo! - 6/10/2003 12:46 PM   
av8tor1977



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Status: offline 		Hi,

Well, it's a little noisy, but not as offensive as a stock muffled .61 at full tilt because of course, it's a lower tone. I think you could get away with it at most fields.

Yes, convert yours Adam! By bolting the prop directly to the crank, using the CH ignition with a little hub for the magnet in back, and trashing the stock muffler, it comes out pretty light. I think this will haul my Big Stick around with ease. And with a throaty sound, $2.00 a gallon fuel, and NO flight box to tote!

I should have another digital scales on hand later this week, so I'll let you know exact weight. Like I said at one point, my custom Big Low Stick hauls a 35mm camera around like it's not there, so I don't think I have a problem if this weighs a touch more than the setup that I have now. It may not though, when I count the extra (glow) fuel, engine mount, etc. that's presently on the plane with the Fox .78.

Too much fun!

Thanks,
AV8TOR

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don't forget echo! - 6/10/2003 8:36 PM   
kevin28


 

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Status: offline 		What does that muffler look like? A little trick us boaters use is to put some green scotch-brite into the mufflers. (quiets it down nice)

Sounds like a fun project.
Congrats!

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don't forget echo! - 6/10/2003 10:08 PM   
av8tor1977



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Status: offline 		Hi,

Here is a thread with a pic of the muffler:
http://www.rcuniverse.com/forum/tm.asp?m=838546

Thanks,
AV8TORR

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Got a few numbers now... - 6/12/2003 11:22 AM   
av8tor1977



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Status: offline 		Hi guys,

My little 16cc Kioritz weighs 2.75 lbs. ready to fly with my "Jato Tube" muffler, and the electronic ignition including a 1200 mah NiMh battery.

That muffler is a little heavy, so a person could improve on that by a few ounces with an all aluminum muffler.

This is about 1 lb. heavier than my Fox .78 with muffler and mount. As it turns out, this isn't going to be too bad in my case. I'm installing it on my custom Stick, and I discovered about 6 oz. of lead right behind the firewall that I forgot I put there for balance 8 years ago when I built this plane!! I also had the battery installed right at the leading edge of the wing, so by moving things around I hope to add very little tail weight, if any. It will still of course, be about a pound heavier than before, but...

A: It hauled my 1+ pound camera around with no problem whatsoever before. Wing loading now at: 27 oz. per square foot; not a problem. And...

B: If I like this engine, I'm going to convert this thing to a biplane; I already have the wing!

I also think I can get another 500 rpms out of this engine with a few mods, and at that point my thrust ratio will be better than before. At this moment, it is just shy of being equal to before.

And the saga continues...

Take care,
AV8TOR

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Can't wipe the grin off my face... - 6/15/2003 3:50 AM   
av8tor1977



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Status: offline 		Well, just got back from flying my Kioritz 16cc/Big Low Stick at the beach. (I know, life's rough; I even went swimming afterwards and sat on the beach and drank a few beers!)

Anyway, it flies great!! I'm really impressed. This has been a really worthwhile project and I'm having a blast. The engine runs dead steady and pulls really well. The uplines seem a little stronger; overall power down just a hair from my old Fox .78 installation as indicated by my measurements and calculations with Thrust HP. But the engine is stock so there is room for improvement, and more tinkering!

With no changes other than my modified muffler, and the CH ignition, I'm getting 6.9 lbs. of thrust with an APC 15 x 8 prop. Once again, the engine's ready to fly weight including my "Jato Tube" muffler, which is a touch heavy, and the ignition system with battery, came out at about 2.7 lbs.

For me, it works great on my Stick, but then I wasn't looking for a thrust weight ratio like a rocket. This would be super on something like a Cub or other lightly loaded application.

Thanks for all the input and help,
AV8TOR

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don't forget echo! - 6/15/2003 9:45 PM   
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Status: offline 		? to keith bme member.im very much interested in the 30cc gas engine that weighs just over a pound.could you post where i can get more information on this engine.or send me a email.thanks [email]speckledbird9@webtv.net[/email]

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don't forget echo! - 6/15/2003 11:53 PM   
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Status: offline 		I will also like info on the bme 30cc engine.

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don't forget echo! - 6/16/2003 12:06 AM   
Volfy



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Status: offline 		AV8TOR, glad to hear your 16cc Echo turned out good. That's what this forum is all about - maximum smiles per dollar and seeing something with such humble origins turn into a flying machine.

I would try a little smaller prop to get the little engine into its power band. I think 7000rpm is hitting short of its peak torque. Heck, the G23 makes the most torque at around 9000rpm, and mine loves the 15x8 APC. Maybe a 15x6 or 14x8 would be better suited for your 16cc.

< Message edited by Volfy-RCU -- Jun 17 2003 2:05PM >

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don't forget echo! - 6/16/2003 8:38 AM   
av8tor1977



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Status: offline 		Thanks Volfy. I'll try that.

I love to tinker, and I have a lot of room with this as I haven't touched the compression, port timing, nor carb.

Thanks to Adam, I have a larger carb to try, and will be checking the port timing, raising the compression, etc. soon. But all in all I'm impressed with this little engine and would recommend this to anyone.

Next, I think a GSP Katana 72" with a 42cc Poulan!! I've got my eyes peeled for more "Echo" engines too!

Take care,
AV8TOR

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don't forget echo! - 6/17/2003 8:41 AM   
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Status: offline 		av8tor1977
May have missed this in earlier post, but was your engine new before your conversion or a used repair shop. yard sale special?
Glad it worked for you!

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