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.

RE: Project poulan
 

Hey, I havent recieved the new ring yet, but I have got the engines that Combat sent me. He sent 2 short shaft engines and one long shaft engine. I have read that the long shaft engines produce quite a bit of power, so I am going to test it out tomorrow. I measured the exhaust duration, and it was around 140 stock. Since I damaged the gasket and dont have a replacement, I am going to use the three bond. In order to retain the original specs, I ported the exhaust so that without the gasket, the duration remains at 140. Its not a bare bones stock test, but I figue that its close enough. There are many threads already done about the stock performance of this engine. removing the gasket to increase compression probably yeilds marginal gains. I also dont have a backplate gasket, so I used the three bond there as well. Im kinda excited to see what kind of numbers I will get. The test prop will be the 16-6 prop. I cant use my 16-8 cause I had to drill the center hole out to fit another engine that I have.
I am going to charge my camera up to make sure I get a video for you guys. Dont worry, I will edit out any poor camera work.

RE: Project poulan
 

I test ran the engine this morning. It wasnt too bad for power. I was getting 7400-7500 on the 16-6 apc prop. Again, the only thing different from stock was the carb, muffler, no head gasket and no backplate gasket. It isnt a "bone stock" test, but its close enough. I am uploading the video to youtube as I type this. It takes a long time to upload, cause the video is in HD. I have torn the engine down, and am going to port it some more. I doubt that I will run it again today, but ya never know. The new ring hasnt came yet [&o] I really wish that it didnt take so damn long for stuff to cross the border. I expect it to be here next week. Frank said it usually takes about 10-14 days to get here. Another thing that would help the engine that I tested today, would likely be a new set of rings, but I want to try a few other things first. I also kinda want to get a header bent up for this thing, and try a canister. I would like it if the engine was a bit quieter at WOT.
Another mod I want to try is changing the timing of the transfer ports. In stock configuration, the tops of the transfer ports are level with the top of the exhaust port. When I increase the timing of the exhaust, I think it would further increase power if I also increased the timing of the transfer ports. It will be a b**** to work on them, but I am very interested in this mod.

RE: Project poulan
 

here is a link to the video. Enjoy.
I have already modified the exhaust again, and im going to run the engine later on http://www.youtube.com/watch?v=THTsSHFXWII

RE: Project poulan
 

Just got back from testing. Not much improvement. I think that I need to work on the intake. It seemed like something was "holding it back" Im going to search for a good starting point for intake timing. Im also going to try modifying the intake manifold as well.
One thing I thought of doing was cutting grooves in the manifold (kind of like rifling) I think Edelbrock makes a carb spacer for small block engines that incorporates this design. They claim that it improves power by helping the fuel atomize better. I dont know if it will help a 2 stroke as much, but its worth a shot i guess. I have lots of manifolds, so if it doesnt work I can replace it.

RE: Project poulan
 

You may want to try a velocity stack.

With the Carb. right in the prop wash it's hard to tell
if you have the vapor dancing in front of the Carb. or not.

They can be good for a couple hundred RPM plus it may fatten up your mid-range.

A flat washer and a short piece of pipe makes a velocity stack.

RE: Project poulan
 

I am going to get a velocity stack made up this week.
I did a little porting on the intake. I increased duration by 10 degrees (I think its at 130 or 140) I have it written down at home. (im at work right now) I did test it again close to dark. it still got the same rpm. When I ported the intake, I also took some material off the top of the port and sides to enlarge it. Unfortunately, I took too much off the top, and now it is barely open when the piston is at BDC. This lets the exhaust escape out of the intake as well as the exhaust. It sprays quite a bit of fuel out when running. I was kinda pissed at myself for doing that. Before I headded in, I took the exhaust off, and the fuel didnt spray out as much, and I also got an increase to 7800 rpm. So Im thinking, cause the jug is pretty much garbage now. I am going to try to increase the exhaust by another 10 to 20 degrees and see what happens.
One thing I noticed on my short shaft cylinder is, the Intake port is slightly larger than the one off the long shaft engine. This could mean better potential for this engine.
So, for monday, Im going to go to a machine shop and see if they can do a couple things for me: Make a velocity stack and Bend up a header pipe, so I can use my home made canister.
I think the canister will help because I built it for a much larger engine, so the backpressure will me minimal.

RE: Project poulan
 

I recieved the Frank Bowman ring today, and got a chance to test the first engine. Power increased by quite a bit. I was getting a good 7700 rpm with the apc 16-6. I know the ring is still seating, so I didnt really go all out. I would like to increase the duration of the intake, but am afraid of ruining this engine. I guess I could assemble one of the other engines, and try out a few mods. I blueprinted my stihl 25cc the other night, and the exhaust on this engine is about the same as the stihl. The intake is about 10 degrees less duration than the stihl, so I kinda want to change it so that it matches the stihl. Then I will test it, and if I feel it needs more power, then I will look at the transfer ports. I also need that velocity stack, cause there is a bit of fuel spraying out the carb. I think I will make an "el-cheapo" one tomorrow.
I have a small video that im uploading, and will post as soon as its on youtube.

RE: Project poulan
 

Well, its really late, and I cant really sleep cause Im thinking about the mods to this engine too much.
I just realized that my initial test with this engine was with a JXF 16-8 prop. After the new ring I havent compared it with the same prop or gave you guys any "real world" improvements. Tomorrow, Im going to try the 16-8. I also fixed my muffler. I also added another tube. (i think it was too much back pressure with only one tube)
So far the mods for this engine include:
1) bigger carb (WA19A "27/64" ) 2) made a 1/2" hole in the muffler to increase flow 3) Removed head and backplate gasket and used thinner ones (that three bond stuff doesnt work very well) 4) Increased exhaust port size and timing (by using thinner gasket intake was also affected) the timing is: Intake open 299 degrees Intake closed 62 degrees Exhaust open 107 Exhaust closed 255
Intake duration 123 degrees Exhaust duration 164 5) Frank bowman ring

Now for my question...
I checked the intake duration against my stihl and the POULAN is at 123 and the STIHL is 116. But the stihl intake opens about 7 degrees sooner. Should I advance the timing of the intake any more?
Has anyone ever messed with transfer port timing? If so, how did you measure the duration and if I advance it too far, how will it affect the engine?
thanks alot,
andrew

Here is the short video from today http://www.youtube.com/watch?v=luLYADYo3Ek

RE: Project poulan
 

I test ran the engine again today. With the 16-8 rpm dropped to 7000. It seems like I lost some torque with the increased duration. Also, the ring needs to seat more. I put the 16-6 back on and ran the engine at about 3500-4000 rpm for about 30 mins. I then tested full throttle again, and rpms were up to 7800. I think most of that improvement was from the exhaust modification. I let the engine run for about an hour total today at low throttle (mainly to keep the heat down) and on my last rpm check, I was getting 7998rpm! I think with a bit more run time, I will have got the 8000 rpm that I want.
I have decided to leave the transfer ports alone, and am going to run the engine as is. I got the target power that I need. Once I can afford it, Im going to order an XYZ CDI for this engine. I think that rpms should increase as well, cause the heavy flywheel wont be holding it back. I also still need to get a header pipe made up, and a velocity stack. That probably wont happen for a week or two.
For now, Im going to modify one of the other cases for EI use and get one of the flywheels center cut out.

RE: Project poulan
 

When breaking in an engine, it's the heat cycles that break it in.

The heating and then cooling of to the surrounding tempature.

So run the engine to the working Temp. and let it cool.

Anyway that is what some experts say.

Just my $.02 worth

RE: Project poulan
 

I didnt run it for an hour straight. I ran it for about 10 mins, shut down, let it cool, then started it again. I really wish I had a plane ready for it. It would be much better to break it in in the air. I guess thats this winter's project...
Depending on the day, I might run the engine again tomorrow. I took a different intake manifold, and drilled it out to match the same size as the carb. The other one was just a stock manifold. It might make a bit of a difference.

RE: Project poulan
 

Hello
see it

http://www.rcuniverse.com/forum/m_30...tm.htm#3082557

an englishman have a link to http://www.rcmf.co.uk/
in this site the men "diablo" (avatar in RCU) convert a Poulan, you must read to find the link, I can not find, also you must be logged in rcmf.uk to see the Poulan conversion, nice to see, new tricks, the better how to balance flywheel (magneto) sorry my english. Do a reading in boths links, is worth.
Also see
http://www.rcuniverse.com/forum/m_31...tm.htm#3192059

for newer Poulan 25.
I come from flying field 2 hours ago and my Poulan reached 63 hours flying time. So sweet .
Happy landings
Jose

RE: Project poulan
 

Thanks for the links. Im awaiting the approval from the website. It seems that I did go a bit overboard with the exhaust. I also need to advance the timing of the transfer ports. I think I might do that tonight. I would like to turn the case down for more compression, but I dont have a lathe. I do have plenty of power for the project I am going to do, but more never hurt anyone....
If I get the mods done, I might get to run the engine tomorrow. there will be a video, if performance is increased.
One thing I dont really get, is why this thing is a dog with the 16-8. It should have improved. The more I think of it, the more it frustrates me. I dont think I can fit a 16" prop on the plane im going to build, but I would be happy if I could get 7500 or better with the 16-8.

Is there a big difference between the poulans with the bolt on mufflers and the ones with the springs?


Word removed by moderator

RE: Project poulan
 

The best results usually come from:

Bowman Ring

Exhaust timing 150 degrees.

Matching the transfer ports between the case and the cylinder.

Opening up the stock muffler. In your case I'd braze a 3/4" tube in place of the existing out let.

A Carb. with 2 mixture screws. 3 or 4 MM bigger at the most. A smaller Carb. will cost you a few RPM but will transition better

Transfer ports are usually pretty good. You might try to square them up, I don't suggest raising them.

Remember more is not always better.

RE: Project poulan
 

This Poulan thing just hit me, I stopped by my favorite Auto Parts and other things store today for some metric cap screws and the operator ask me if I would be interested in a Poulan Chain saw for parts. "SURE" Well, when we got in the backroom, he unloaded three Poulan Pro saws on me just to get rid of them. A 35, 42 and a 45. The 35 and 42 had an exploded or broken spacer washer in the centrifical clutch, and the 45 had an out of round centrifical clutch housing. There are some other minor problems, but all very fixable. I had the 35 and the 45 running in about an hour, but need some additional work on the 42. It appears to me that these may be a very adapatable conversion engine. What can anyone tell me about them. All are near new. I am a Ryobi nut, but???? Flathead 4