I'm not finished reading the thread (many threads to read, and too little time!), but I'm not particularly interested in mixing fuel or running glow. I prefer to use just gasoline and oil. By the way, I bought some time ago an oil specially made for chainsaws and such, I don't know if it's of some good or not for those conversions - I think, though, I may be better than a common 2-stroke oil. I also plan to pour some castor oil on the mix, it's a good product and gives it that "racing smell" I love so much!

Thanks for the links and pic! A new and interesting addition to my virtual library!
I'm just a bit confused about the position of the transfers in the pic. Assuming the black line represents the stock exhaust port and red lines the modded port, there are no transfers there. They are, in fact, about 85º apart, so unless I grinded a lot they are not affected by the port modding. Anyway, I'm starting to think those "radical" mods will be put into practice in a future engine. I have waited many time to have a working gas engine, so I prefer to s tick to the tested stuff for now.

I found the thread! LIST OF 11MM CARBS HERE!!
There's an overwhelming amount of carbs there, even if I only count the ones with 2 needles by Walbro (all the smallest series of diaphragm carbs are in the link). There must be some differences! I'm sure a series of carbs is better suited for our use, for example. So choke, yes or no? What about the primer? I don't think I'm going to need them, but the weight is neglectable and they may come handy some day. Well, I think I'll toss a dice or two and pick up one or go for the WA-167 I've heard about.

Regarding the exhaust, I've made a simple calculation about the exit area. My pipe has an ID of 16mm, with area of roughly 200mm^2. The resulting area for yours are 97mm^2*2=194mm^2 (7/16) and 127mm^2*2= 254mm^2 (1/2). Maybe a bit on the low side? However, I still think factors like exhaust shape are possibly of more importance than that. I can try to make several mufflers using the "box" or "mousse can" techniques, or go ahead, buy some equipment and custom weld my own, but that will be when I finish many of the things on my to do list! There's a certain exhaust noise I'd like to have in my planes! - if you think about it, it's kind of a signature!

Nice link Mikenlapaz! I'm searching now for the other one, the Echo thread. Let's see what I can learn from there!


Can you further explain the "cylinder lowering", "transfer ports cleaned", "gutted exhaust", etc. (if it's not a secret engine modding!!) In a few days I'm reading many new stuff for me. BTW, I found some Homelite 30cc info you posted in previous treads. I post them here since you posted them before in a public place, but if you like me to remove them for some reson just let me know.

"ï€* My highly souped up Homelite 30cc turns an APC 16 x 8 prop at 9400 rpms. It hauls my 12 + pound Ultra Lite Stick 120 around with great aerobatic authority. I'm sure it would be good at hovering if I propped it with more diameter and less pitch but I like the way it flies now as I'm not really into 3D. "

"ï€* Hi,

Here's the stats and a pic of my Homelite 30cc . It turned an APC 16 x 8 prop at 8600 with only an opened up muffler and a slightly larger carb. Then I modified it...

Homelite 30cc - older design with small transfer ports.
Weight with muffler - 2 lbs. 14 oz. (More cutting/grinding on this one than my Homey 25cc, and this is with prop adapter but without prop or spinner.)
Muffler - Stock, square, gutted, with two brass 1/2" i.d. outlets added.
Carb - 11mm Walbro, manifold ported to match, external pulse line.
Ignition - CH Ignitions electronic set at about 28 degrees presently.
Cylinder - Quench or Squish band removed, cylinder to head clearance set at .020"
Port timing - Exhaust 165 degrees, Intake 148 degrees, Transfers 120 degrees (22 degrees blowdown). All ports cleaned up and entries in crankcase smoothed.
Crankcase- stuffed to .020" crankpin/backplate clearance.
Rings - FRANK BOWMAN'S!!
RPM - APC 16 x 8 = 9400 (Possibly more with tuning and more run time. Also, with this port timing, a tuned pipe would probably give 800 more.)
Test conditions - 4200 feet altitude, temperature 78 degrees, barometric pressure 29.75"

Please also note that while I did modify the transfer port timing, I did not alter the size and I think this would also help. I'll do that on the next one for sure, or use a later model cylinder with the larger transfer ports.

I like it!
AV8TOR"

Those numbers belong to another thread (don't remember which modeller):

"ï€* Here are some numbers from my 30cc homelite . I did not alter the exhaust port and just used a little thinner head gasket, wa-167 carb. The rest of the mods are described at the top of this page. The thrust # comes from a digital fish scale and are approximate.
zinger 20x6 7600/16lbs 12oz
top flight pp 18x6 7600/16lb
top flight pp 18x8 7200/16lb 2oz
apc 16x8 8900/ 16lb
zoar 18x6 8100/17lb 5oz "

Well guys, I thank you again for all your help; all my old questions are nearly solved. I'm learning a lot of things and I'm sure that will pay off soon. For now, I'll keep reading and trying to put into practice all that has been said, and then come back with my results. I'll ask one more thing, so I don't lose my bad habit of asking: how much traction can I expect the engine to have? I'd like to have a rough number so I can resize a project I'm designing accordingly.
Also, if someone has one of those big bore carbs for spare, I'd gladly buy it. I've sent an email to Carrprecision but after 2 days or so I still got no answer, so I'm not quite sure they want to do business overseas. Perhaps they don't like to be asked about their products. Who knows.

Have fun!