Project poulan
 

Hey, I just picked up a weedeater featherlite 25cc engine the other day, and decided to do some testing. I did couple mods right off the hop, like putting a thinner gasket on the backplate, making the exhaust port bigger. (the port is an eliptical shape, so i used my dremel to make it the same size. I also took about .010 off the top of the port to increase the timing. I didnt check with a degree wheel so im not sure what the port timing is. I drilled a 1/2" hole in the muffler, and used a bigger carb (walbro WA19A)
So far its not as bad as i thought. It spins a jxf 16-8 prop at 7200 rpm and idles a bit high at 2600 rpm.
Im running it on avgas mixed 32-1.
here is the video of the first run. I didnt have time to edit it, but is not bad.
http://www.youtube.com/watch?v=Yu7YgABmKXk

RE: Project poulan
 

Hello
I have my Poulan 25 cc stock inside, original throat carb enlarged at 9.5 mm diameter.
Nice, more than 50 hours flown, logged in a small book each flight and the problems I have , only one bad plug and dirt in the carb because use cheap filter, now use MANN motorcycle filter.
Very sweet, I am use props hand made because the props are expensive, with the price of 5 props(yes five) I can buy a new Poulan. For this reason number can not compare.
Have a plane, a bit more than 6 kilos, 1600 sq in, 80 in wing span, very relaxing flights, the plane fly better than I.
Happy landings
Jose

RE: Project poulan
 

hey could you show me a pic of one of your hand made props? I have never dared to tackle a job like that

RE: Project poulan
 

Hello
this is a pic with hand made props, pic is not good to show fine grain of wood, lenga in spanish. At sun are beatifull.
With my learning I broke more than 10 props.
Test show me that the better is 17X7 square tips, near 1 inch wide , proven Clark Y airfoil.
Also made of other wood like alamo.
There are no dificult to make with simple woodworking hardware, and better if you know that with 4 or 5 you can buy a new engine.
I see your video, nice starts, mine is very hard to start by hand,I put and adapter for rope start, nice.
With the metal(steel) muffler of fly poison have a nice metallic sound , nice for two stroke lovers.
This engine is sweeeet. I am using stock air filter and choke levers, nice to choke and my flying field is only dirt. And windy, imagine.
All I know I learn in RCuniverse and other sites, because when I start to convert I am the only one around 300 miles or more.
Put to fly it and enjoy the relaxing flights of Poulan.
Do not modify in excess, because you can lost the sweet 1/3 bottom range of this engine
Happy landings
Jose

RE: Project poulan
 

Thats really cool that you are able to do that! Have you tested that square design against a round tip? I would love to be able to do something like that, but am lucky enough to have time for converting engines.

RE: Project poulan
 

I have found that Poulan engines like plugs with a "J" tip on them. I've gained as much as 400 RPMs by changing the plug.

RE: Project poulan
 

"J" tips? You mean the spark plug? right?

RE: Project poulan
 

Hello
Yes I tested this props, 16x6,16x7,16x8 round tips, with tapered chord from half span of the prop(sorry my english)
After I see Hercules C130 props, near square and with KISS system I made square tips, and compared with the firsts I have aproximately 20% more static thrust and is easier to finish with square tip and constant chord.
Also I have in my club a prop of and old warbird in display and it is with square tips.Dont know the plane but it have(now painted over)all the warnings in english , typical made in USA.
After trial and error I find 17x7 is the best for my plane and use it.Remember I like relaxating flights , sunday flying,The power and thrust from the engine and prop is enough for me.
Its is like a big trainer, slow and sweet, open throtle and it is happy but manageable.
Happy landings
Jose

RE: Project poulan
 

Whoops! I had it wrong It's a "Y" extended tip electrode. Like Champ. RCJ6Y. The Y stands for extended ground electrode.

RE: Project poulan
 

Ok thanks. One thing i do to my spark plugs is file the sides so there is a good sharp edge for the spark to arc to. I read it in a hot rod magazine. I dont know if it increases rpms or not, but it produces a nice clean spark which helps for easier starts and a better idle. I would show a pic, but my digital camera is buggered and i got to get a new one. I might do a diagram in paint to give a rough idea

RE: Project poulan
 

andrew,
Have you personally noticed this on your spark plugs. Interesting, might try it and see for myself.
Edwin

RE: Project poulan
 

here is how i modified the spark plug to look like:

RE: Project poulan
 

Another update on project poulan. Today I was staring blankly at my engine bored out of my mind and i got an idea. I decided to try it on gas/glow. At first, I was having trouble starting it (mixture was waaaay too rich) and with a bit of fooling around, i got it to run reasonably well. Power increased to 7400 rpm on the same 16-8 prop, and i didnt get a reading on the low end. I didnt get to really tune it, cause my bloody glow driver died on me. Now im wondering if i will go to EI or not. I figure that with a 15-8 prop, it will increase the rpms quite a bit (maybe to just over 8000? ) and it will make the engine lighter. Set up on gas/glow, it will weigh about 2.5 lbs give or take a few oz.
The plane i want to put it in will be a sig smith miniplane enlarged to a 64" wingspan. I havent started the build yet, but hope to in the near future.

RE: Project poulan
 

Hi andrew66,

I almost converted one of these to glow.Then I thought with glow fuel at the time 20.00 usd a gallon no I will just stick to gas. With the amount of fuel it will go through would it be worth it ?


regards

Charlie

RE: Project poulan
 

Gas/glow cost me roughly $11.00/gallon. I pay about $24 for a gallon of 10% glow fuel, and premium is about $1.15/L. Fuel consumption isnt too bad either. Way better than straight glow fuel, but still more than gas.

RE: Project poulan
 

Well, I couldnt get a 15-8 prop today, but got a 14-8 just to try. The good news is: It spins it @ 8400 rpm, the bad news is: its a 14-8 [&o] Im not sure if it will be enough power for the plane i want to put it in. I might make a setup so i can measure thrust. I personally belive that its the amount of thrust produced that will determine how the plane will fly. (Pitch speed also plays a factor, but i dont think as much) Im going to order a 15-8 and see what numbers i will get. I might ask a few club members if they would donate a prop just for testing.
If i dont get at least 7700 on a 15-8, then i will start to do more porting. I also need to get a new muffler, cause the one i have, has a crack in it which is causing oil to get all over the engine. (at first i thought the case gasket was leaking) Im also going to order a frank bowman ring cause compression is still low.

RE: Project poulan
 

Hey, tomorrow, im going to do a thrust test of my engine (with the 14-8 and 16-8) I built a makeshift stand to do this with, and was wondering if anyone would be interested in a video? I am hoping that i can get 12lbs of thrust out of this engine.

RE: Project poulan
 

By All Means! We want video.

RE: Project poulan
 

Sorry i didnt get video. I forgot to charge my camera. The test went ok, but i need to improve the performance of this engine. The 14-8 only put out a mere 7.5 lbs @ 8300rpm, and the 16-8 did just under 10lbs @ 7200rpm. I was thinking about this engine after, and was wondering at what rpm the rev limiter kicks in? it doesnt surge or piss around at 8300. When the limiter is hit, does it just stay at a steady rpm? or is it kinda like a car? I honestly think that if it will turn a 16-8@7200 it should spin that little 14-8 a little more than that. I ordered a 16-6 today, to see what it will do. I get my props at a very good price, so i would rather try everything before tearing down the engine again.

RE: Project poulan
 

Andrew66,

does this engine have the stock mag? what makes you think there is a rev limiter?

Charlie

RE: Project poulan
 

Sounds like you are getting simmilar results as I have. I would suggets a cdi ignition. If you search the net you can find them cheap. The rc exl units work great. You will get a better idle. For the battery pack I have been making all of mine with consumer NiMH AAs. They give 2450 mAH for only $12. I have had no issues with soldering them. My engine is giving the top end speed is what you are getting. I do need to use a a starter because the compression is so low. I run Coleman camp fuel. It stinks less than gasoline, that is my only reason. I find california blend gas really offensive. The Coleman octane is only 40. There is no need to run high octane fuel, it justs cost more than regular gas with no benefit.

RE: Project poulan
 

I want to run this on CDI, but i want to make sure that it will live up to my expectations first. I run avgas, cause i can get it a little cheaper, it doesnt stink, the shelf life is something like 3 years, and i LOVE the way it smells when burned. I havent had any trouble with plug fouling, and I have roughly 3 hours on this engine. If i have to take the spark plug out every gallon and clean it, big deal. I am measuring the timing of this engine, and I really hope that my numbers are wrong (I did some pocket porting before) The exhaust opens at 66 degrees, and closes at 256 degrees. that gives me a duration of 190. According to what ive read, it should be at 150ish. The intake is around 126 degrees duration. I dont think there is anything else i can do as far as porting. I may actually have to get someone to turn the case down in a lathe in order to get the exhaust timing back. I guess i learned my lesson. Always always always measure the timing before cutting. Oh well...

RE: Project poulan
 

Here is a good sparkplug mod. Capt,n

RE: Project poulan
 

Thanks for the pic. That is very similar to what was shown in the mag i read (chevy high performance)
As per the timing issue, I removed the gasket completely and checked again. Now the exhaust is at 180. Just for the hell of it, i decided to check what the timing was on my Stihl 24.5cc. For the little amount that i have run it, it seems like a strong engine (the heavier alternative to the poulan) and the timing on it is very similar +/- 5 degrees. Im going to clean up the port so it looks a little nicer, and so its nice and straight across the top and bottom. Im also going to get a smaller bit and try and square up the corners of the port a bit to give it more surface area. The piston also travels just a bit past the bottom of the port when its at BDC, so im going to remove that as well. Then if i have time today, I will try and test run it again. My new prop should also be here tomorrow, and i have charged the camera up, so I will try and get a video as promised.

RE: Project poulan
 

I ordered a frank bowman ring yesterday, so im hoping that it doesnt take too long to get here. I also picked up some "threebond" similar to yamabond, so i can do away with the backplate gasket and the head gasket. My 16-6 prop arrived today, so I cant wait to get this thing on the test stand again. I decided not to run the engine again til the ring came. Also the weather here has been just awful. Where the hell is summer? I think im also going to get a carb kit. I noticed the last time I ran it, the idle was pretty poor, and it would pick up and slow down. Kind of a brummm...brummm...brummm. Just like I was slightly reving it. I guess i should have got a video, so you guys could hear it. I pulled the diaphram cover off, and it looks good. I suspect that there is some crap in the carb. I forgot to put a fuel filter in it. (was in a hurry and had changed the lines) So i guess this is how i pay for cutting corners.