ok, I'm further into the conversion, stripped for gas/glow with 15x8 prop it weighs 2 pounds 3 oz.

right now I'm working and pondering porting the thing, I just measured the exhaust duration at 113 degrees, intake duration is 107 degrees, I guess I'll figure out a way to measure transfer duration tomorrow as it's getting late... the plan so far is to increase the exhaust to around 145 degrees, and increase the width of the intake port, and that's about as far as I got on the planning part.

it turns out when you take the jug gasket out and try to degree the engine, the piston hits the head, I'm planning on running a very thin gasket if any gasket, so I guess I'll chuck the piston up in the lathe and turn the edge down some.

I'm willing to try any tricks on this thing, I've got several small carbs that would probably work fine on it (like stock 25cc carbs), it has some light scoring on the piston and cylinder so if it doesn't work it's not much of a waste. I just like the looks of the little thing, so it's a little rough around the edges with the weight loss program of choice (pliers), but I'm curious what it'll do once screwed with...

Pliers...lot faster with horse hoof TRIMMERS! Capt,n

As you know as long as the scoreing is below the exhaust port it isn't a real problem.

The first thing to check when working on a used engine is the ring gap. Every used engine I've taken apart without exception had a ring gap that was too wide. This costs power bit time. Stock specs for ring gap are around .003", which is VERY tiny. It's not uncommon to take one apart and find a ring gap of more like 1/8"!!

Frank Bowman's rings go in all my engines. I have taken an otherwise good running engine, but with a bit wide of a ring gap, and replaced the ring with one of Frank's, and gained almost 1000 rpms! All the trick modifications in the world won't help an engine that doesn't have a good ring seal....

BTW, Frank actually specs ZERO ring gap for his rings!

Have fun,
AV8TOR

Hammer House of Horror for engines [sm=lol.gif] At least I give the poor things swift service with a hacksaw and a swig of rum!

Hoof clippers !!!

Featherlites RULE. .40 size Twist with 21cc Featherlite. All the porting mods but stock ring. Best way to reduce weight? Don't use a heavy prop hub. Just have the thrust washer fit the taper, put on prop, prop nut on crankshaft....same prop drive as glo engines. Throttle coupled spark advance. I've gathered up a bunch of these, older style, bolts better to firewall.
Also no backplate. Just run bolts from rear of firewall through rear cover and into engine. Got one for my H9 Camel, Great Plane Tripe and my Great Planes 80 inch Cub. SWEET.

Wrong pic, here's a cloer shot

Where does one buy a .40 Twist? Is that a Goldberg kit? Thanks Capt,n

Here ya go Captain: http://search.horizonhobby.com/index...d=117A4F5683E5

Joe, That installation is beautiful!

So you took a chunk of thickwall aluminum tubing, turned it down to a washer and cut the taper????

Or were you fortunate enough to find something that worked?

I'm looking at gas-glow to shave as much weight as possible and I really like your idea.

BTW, what prop are you running on that 3D beastie?

Hello Team Monkey, 15 x 6 Zinger prop. The thrust washer/pulse wheel (holds the magnet) is made fron 1/4 inch aluminum. The prop nut is a DuBro 5/16 x 28 hobby shop item. I turned the front of the case for the pick-up wheel (holds the pulse switch for the ignition), and cut a groove in front of it for a snap ring to hold it on. It (pick-up wheel ) is connected to the throttle so spark timing advances with advanced throttle and retards with reduced throttle. Just like the older Brison set up. thanks for the interest, Joe Buitch

One of these days I'm going to learn how to cast aluminum. One thing I would really like to cast, is a 90 degree elbow to mount the carbs facing rearward to make these piston port engines a little narrower.

I know someone is likely to say "Why not mount it facing forward for a ram air effect?" First, that messes carb calibration all up. Secondly, I have read that even at well over 100 mph, the power gain from ram air is only around 1 to 2%.

AV8TOR

Thanks for the info Joe. Mine will be mostly stock except for the gas-glow so I bought a 14x6 as a starting point. With no port mod's that's probably a fair place to start. Once it's warm enough to get back in the garage[:@] I'll get under way!

ok, the scoring might be worse than I thought, it's about a 1/2" wide by 1.5" strip of scoring going from 1/4" below the exhaust port to the top of the cylinder (like it's following the ring)and it's from the middle of the exhaust port to just past the edge... I'll clean it up and if if doesn't run, I'll chock it up as porting practice... not to mention the ring gap is .015", if the thing actually runs, I'll get a bowman ring for it

if anyone was curious, the engine is 2 lb even with everything but glow plug, 1 lb 12 oz with everything but glow plug and prop. apparently pulling out the two steel plates from inside the muffler and the choke plate made some difference.

That's pretty light! I may have to try one of these someday. Port it, new ring, etc. and see how it comes out. My brother had one a while back and I told him it wasn't worth converting. Maybe I'll see if he still has it and convert it. It would be cool if it would put out enough to nicely power a .50/.60 size plane.

AV8TOR

Hey AVTOR, one of the guys at the field has a GP .60size Big Stick with a 20cc Zenoah on gas. I flies great! (we are all stick nuts and have sticks from 48" to 96") The Big Stick will easily do a Poulan 18- 22cc done like you are talking about, just tri-stock the fire wall real well.

I had a Giant Big Stik with a Poulan 42cc on it. That was fun. I took the Poulan off of it recently, and put my 48cc twin on it. Too cool!!

AV8TOR

I was just wondering because I've heard conflicting answers.

When using bearings with the rubber seal built in, do you still need to install the original seal too.

AV8TOR, that should be TWO cool! I have a GB Stick with a 46cc Poulan on gas, has unlimited vertical. A twin on gas/glow muat be AWSOME! What size prop does it spin?

I've been running a little 18 x 8 on it that is obviously too small. It will probably end up with either a 20 x 8 or a 20 x 6-10. It has a smoke system on it, which is fun, and it sounds fantastic!!

Ralph -- Well here's my thoughts on that. I wouldn't particularly trust a sealed bearing to stay perfectly sealed on a two stroke, and if it didn't, the secondary compression/vacuum leak would be problematic. And if you use the sealed bearing AND the seal, I would be afraid the seal would burn out for lack of lubrication. So, (once again if it were mine), I would use a regular bearing and a seal, or if I were stuck with a sealed bearing, I would take the seal out of it and then run a separate, dedicated seal. Just my two cents....

AV8TOR

ok, the 18cc was toast, I doubt it would run with how it was scored, the good news is after I did all that work converting it, the piston and jug from a 24cc poulan is a direct bolt on, added my stripped carb adapter and pulled the plates out of the muffler and it's at 2 lb 4 oz, so apparently the 24cc is 4oz heavier than the 18cc... the only things different than when I got the weight on the 18cc is the studs I stuck in the back and the wingnuts I used to hold it on my test stand... this is with prop and everything needed for gas/glow

hey i converted a 27cc stihl and it flew the same plane great i have some pics around i can dig up it would do aerobatics no 3d stuff but uplines were good and weight i moved some batteries around in the plane