1st conversion, tips and help?
 

I was given an old craftsman 2.3/16 with a bad s.s.module. Ive recently found out it is a poulan micro 25. The cylinder,ports, and piston seem to be in excellant shape. Ive ordered the new module, it will be here in a couple days. Then Ill try to fire it up. I dont know, but presumming it is 25cc? I have some cutting and grinding to do on the case and flywheel. Anyone done one of these? Im curious on the peformance stats. I would be gratefull for any tips and help you all could give. when { or if} I get this one going, I have a newer poulan { a little bigger I think} out in the garage that will be the next project. Ive got two big birds in the shop Im hoping to use them in. A Bryons christen Eagle and a scratch 97 in. wing GeeBee model E. Both birds are under 14lbs. Im hoping these engines will be the power they need. Thanks again for any tips and insight I may recieve! Al

RE: 1st conversion, tips and help?
 

go-veret
hey, Im no expert but Im pretty sure that a97"anything will need more power than a 25cc engine
Ihave a 84"edge540 with a homelite 45cc and it could use more power.also what is a craftsman 2 3 \16?
or is it a 2 3\16 "what?

RE: 1st conversion, tips and help?
 

most bipes will need twice the cc's than any plane in comperable size and weight. and you will notice on the GeeBee you wont get quite the performance from it you would want but it will possible loft it in the air. if you can find a 45 cc poulan it might work well with both planes.

RE: 1st conversion, tips and help?
 

flyjoe; The saw just had a decal on the side, 2.3/16 . I had a heck of a time trying to figure that out. But I ran across a place out of Maryland ,when I sent pics, said it was an old poulan micro 25 but im not sure what cc it is. My Gee bee I figure with engine will weigh about 14lbs . If this motor is a 25, It wont be enough? I had an 1/3 eagle before, with a quadra 35 and it flew nice,but lacked the pulling power. So I know it will need at least a 45. I have just finished a TF 47with flaps, maybe the 25 would be better in it ? thanks, Al

RE: 1st conversion, tips and help?
 

Which is better to convert a saw engine or a trimmer? Ive seen and heard preferances on both. And whats the mojo on gettin an easy hand flip start? Do the flywheel fins need to be ground off? Do I cut off excess casing around the basic block? Can a hub be too long or short, or make the hub to the cowl opening?

RE: 1st conversion, tips and help?
 

basically if you are using the flywheel you need to cut the fly wheel fins down some people remove the fins completely even. make sure to balance the fly wheel upon doing that. the casing can be ground down to a certain extent on most engines. just dont make the mistake of accidentaly grinding away where the magneto pickup mounts or your flywheel is useless. i have seen some that converted thier engines for glow and removed alot of material so if you look at those for a guide as what can be removed again i warn you have to keep the magneto mount so you cant remove quit as much as others here. im not really all that sure about chainsaw engines because as far as i know chainsaws have more torque and are more powerful but i am not an expert there. the decal might be 2.3/16 as in 2.3 ci / 16 cc but that is not exactly right because 1 ci. = 16.39 cc but 2.3 is more like 38 cc or close to that. magneto engines are difficult to flip start really. when i tested my 25cc homelite i used my glow electric starter which turned the engine over just fine. as far as i have read on this forum you shouldnt have a hub longer than 2 and 3/4 inches. which is usally more than enough to mount the engine and get the hub out of the cowling. if its shorter i dont think with will hurt as long as it clears the cowl and the magneto flywheel is not rubbing on the inside of the cowl.

RE: 1st conversion, tips and help?
 

Trimmers are usually found in 25cc to 31cc range. Saws are easier to find in larger displacement. I prefer blower engines because they often have a more compact flywheel.

Just my opinion.

Bill

Hand propping might look cool but it is a pain in the posterior.

RE: 1st conversion, tips and help?
 

go-vert
I dont want to go too far out on this particular limb, because what may be o.k. for one
guy may be no where near enough for the next .I am presently building a 31cc ryobi for
a 72"yak54 at 12 lbs. and Im being told that Im underpowered .
yes, a saw engine revs higher and has more torque. but you are 2 lbs. heavyer and 6cc
smaller , if this is true then logicly you are slightly worse off than I am .
o.k.next question whats a tf 47?how big? what weight?
next we cut the fins down so it will fit in the cowl and to reduce air load as it spins a magneto
ignition can,in some cases, be started by hand fliping it ,its hard to get enough rpm's to make
the magneto fire the plug. also a fixed timing engine is more prone to "kicking back" which is
hard on the fingers.
keep the hub as short as possible 2-3 inches ,past this things tend to get wobbly and provides
a longer lever for bending things ,like the crank shaft.
recently someone wrote that a saw is designed to run at 10-15000rpms and a trimmer at7000-10000
rpmsand that the 7-10000 range is what props r designed for
I cut off every thing that isnt doing or holding something but i have found that grinding on aluminum
doesnt remove enough weight to make it worth it .like trying to thin out a crank case or triming the
head fins remember its aluminum.if its a BIG lump thats doing nothing then ok but otherwise no .to
save weight try an electronic ignition(pricey) and remove the flywheel and mag-coil ,or bn 120 is making light
weight flywheels(4.5 oz)
one more thing after looking at carlosponti's response it hit me.2.3c.i.d.(or38c.c.) is the engine size. 16 is
inches ,as in bar length .38cc thats pretty good. can you post pic of engine I'm trying to id one but im
not picture capable

RE: 1st conversion, tips and help?
 

ahh now that makes sense. might be an engine to experiment with a electronic ignition then because i think he said it has a bad ignition moduel?

RE: 1st conversion, tips and help?
 

how about if it is a chainsaw it could mean 2.3 ci 16" bar

RE: 1st conversion, tips and help?
 

There are way too many naysayers.

A 25cc engine will fly a 12-pound airplane with authority. I know for sure that a 25cc engine will fly a 25-pound airplane however somewhat dangerously. Much of the way an airplane flies depends on your ability to prop the engine and your ability to tune or modify the engine.

The entire process of converting engines can be viewed as a giant ongoing design experiment. Have fun with the conversion. If after flying you don’t have enough power convert another bigger engine. You will have fun converting the second engine.

Bill

RE: 1st conversion, tips and help?
 

Thanks for all the input! I think you may have got the 2.3/16 . the saw does have a 16in bar. I have some pics of cases and the s.s. mod. for when I sent them to the comp. in maryland for Id . So 2.3 would be 38cc? I got the new mod yesterday, bolted er up and used a matchbook cover to gap to the flywheel. And just turning the flywheel by hand Ive got good spark! I cant show block pics today, a machinist buddy is trimming of the oil tank and excess stuff around the basic case. When I get it back Ill get some pics of it. Flyjoe, theTF47 is a top flite P47 kit I built. I have a ys120 4stroke in it now. Heres a couple pics. It weighs about 9lbs. If this saw engine is a 38cc it would be to much dont you think? My plan was to put this engine in the Geebee then find a 45cc or up for the Bryons Eagle. Heres what they look like.

RE: 1st conversion, tips and help?
 

Sorry, cant load the pics now, it says sites too busy, will try again in a while.

RE: 1st conversion, tips and help?
 

Hey Ken, From what Ive been reading around here is when it comes to convertions, youre the man! would you have a hub and or any other parts I need for this odd engine Ive got? And whats your opinion? Thanks! Al

RE: 1st conversion, tips and help?
 

Bills, Thanks, And yeah, Im havin great time with this convertion! I think weve figured out this 2.3/16 is a 38cc with a 16in bar. My Geebee will est weight out with engine about 14lbs. Dont you think this engine will be enough? And what prop size should I start out with? By tuning and modifications, do you mean carb ajustments? What modifing can be done other than elect. ignition? Thanks! Al

RE: 1st conversion, tips and help?
 

Ill try the pics again. Heres the saw cases. And the Geebee in the bones.

RE: 1st conversion, tips and help?
 

And heres the eagle and the 47.

RE: 1st conversion, tips and help?
 

I am sure that I have or can make them if I don't already have them.

where do you fly in pekin? I have some relatives that live in maplton. And have been to a flyin in bloomington.

RE: 1st conversion, tips and help?
 

A 38cc engine would probably be too much for my style of flying on a 14-pound airplane. Cannot make a judgment about your preferences or the GeeBee. On a 14-pound airframe you might want to closely watch and occasionally inspect the structure especially at the engine mounting and firewall. My general rule is two times the weight in displacement but maybe not for a GeeBee.

A GeeBee is a special brand of unforgiving racer. It probably always must fly on the engine and may glide like a piano. It may not even fly at half throttle. I would put the conversion/experimental engine on a more forgiving aircraft until the engine is well known.

Most change the muffler, which almost always increases RPM and power. Many change the carburetor size. Some change the port timing especially the exhaust. Some change the intake port timing.

Bill

RE: 1st conversion, tips and help?
 

Ken... I belong to a club here in Pekin. We have our own flying field out on rt 98 between Pekin and Morton at dirkson park. About 5 to 7 acres with a paved strip. Nice field and friendly people. Have your friends drop by. When my bubby finishes the trim work, Ill post a pic of the engine and maybe you can show me what else I may need? thanks Al

RE: 1st conversion, tips and help?
 

Bills... Port timing? Intake and exhaust? What is that? Does it create more power? Better performance? Is this something I need to do? Question about the muffler. If I cant find one can I build one? Does it require a vent nipple like on glows? Do you chamber it to reduce the noise level? Is back pressure figured in? Thanks! Al Please forgive the missspell on the previous reply; {bubby} Buddy.

RE: 1st conversion, tips and help?
 

I would suggest leaving the port timing alone. Carving on the ports is delicate and requires a considerable amount of 2-stroke experience. In the beginning stick to changes that are reversible.

I would also suggest purchasing the first muffler and then maybe trying to make one. Ken probably has one that will work.

Bill

RE: 1st conversion, tips and help?
 

Got it back today , here are a couple pics . Gotta head to the bowling alley, will check back in when I get home. Al

RE: 1st conversion, tips and help?
 

Go-verticle, The 2.3 if it refers to cubic inch would equal about 38 cc. 38 cc is actually 2.32 cubic inches. If the engine is that big and from looking at the pictures it could be, you will have plenty of power. I would leave the port timing alone. You need to put a good muffler on it so it breathes. As for the carb on it, again assuming it is about 38cc you need a carb venturi in the 13 mm range and a 34/64 on the intake side. That is an older engine and my experience with them is that the ports are timed very well. Consider that it runs in a saw designed to scream all day long. Consider that a weed trimmer is choked back to prevent over winding the engine if the string (read prop) gets too short and joe homeowner keeps going and over revs the motor. I do many Echo trimmer and saw engines. The saw motors are stronger. I do the same ones BME uses and I am sure he doesn't take the engine apart to cut the ports. However I have played around with port timing and have made some nice improvements in performance. I have also gone too far and killed a few. But I would not even consider doing it if I didn't have the Bridgeport in my garage. Good luck and get some experience with this one and then take another step. By the way Ken Lambert and Scott at Brillelli make fine mufflers. I use them both.

Tim

RE: 1st conversion, tips and help?
 

Go-verticle, found some interesting information for you in my collection. The Sears part number for the saw should be 358.353691 and was manufactured in October of 1983. Made by Poulan. Stock carb was a Walbro WT-3 and the venturi is 9.53 mm. Kind of small for the CC but it is a start. You will find though that a bigger carb will perform better. Case in point, the stock carb on a BME 44 is a WT-201 with a 13.4 mm venturi. I built a 44 and used that carb and the 12 pound Wildhare Edge it was in was insane. Well that was until my 15 year old son reworked it a little over a week ago. :)

RE: 1st conversion, tips and help?
 

Bad landing?[&o]

Bill

RE: 1st conversion, tips and help?
 

Poor hovering. :D

RE: 1st conversion, tips and help?
 

Actually to be fair to him I think the throttle servo stripped the gear. That was the only thing we could find wrong with any of the systems. For a while I thought he got hit and the PCM kicked in and cut the throttle. Then he told me he punched it to pull out and nothing happened. Well sort of anyway!!

RE: 1st conversion, tips and help?
 

tim
darn thats harsh. condolences

RE: 1st conversion, tips and help?
 

Tims220225.....Thanks for the specs! There was no model or serial to be found on this engine. Im hoping it is the 38cc. When you start talking venturi sizes, thats a whole new book of questions for me. Going to a 13mm, is that getting a new carb? How do you tell what size is on it now?

RE: 1st conversion, tips and help?
 

I just looked the carb over and found a wt3 stamped on it. Still need to be bigger?

RE: 1st conversion, tips and help?
 

I would say the information I found and the fact the carb is WT-3 confirms that you have the 38cc engine. I would run the engine with the carb you have assuming it is in good shape to get a baseline. You can get a rebuild kit for around 5 dollars or so. Then switch to a larger one and you should see a good gain in performance. Also, this carb has no choke per the Walbro Parts & Service Manual. When you do go to the bigger carb try for one with a choke. If you need a carb let me know, I have dozens and would ship you one for $15.00. I bought 200 of them from a guy that went out of business. Kept the ones that work for plane engines and scrapped the rest. As for sizes etc, the 13 mm or in your case the 9 mm is the size of the venturi on the side of the carb that fits to the intake manifold. The other side has a raised number cast into it. In your case it may be a 20 or 24. This is the size of the intake in 64ths of an inch. Thats about as simple as I can make it. The more you do the more you will understand. What does the engine weigh as it sits?

Tim

RE: 1st conversion, tips and help?
 

Tim... yep your right! it has a 24 stamped on the intake. And I dont have a scale, but I would guess between 3 and 4lbs the way it sits in the pics. So try runnning as is be fore going to a bigger carb? Another question, What prop size do you recommend tostart out with?

RE: 1st conversion, tips and help?
 

You talked about a choke, this carb has a choke plate{mechanical} on it. Is that what you were talking about?

RE: 1st conversion, tips and help?
 

tim220222,

Thanks for the information about carb markings, which was extremely interesting. Learned something new today.

Can you shed light on the following carb markings?

Body
WT732
535

Throttle plate
34-121

Venturi marking – This one is obvious and it measures .408”which is about 10.4.
10.5

Bill

RE: 1st conversion, tips and help?
 

BillS & Go-verticle,

Try the links below. It is the Walbro page link for the WT-3 and WT-731. Here you will see an exploded view of the carb. You are talking about item #14 the throttle "butterfly" if you will. Retail in my 2005 book was $0.79. When you look at this diagram remember that not all carbs are created equal as the picture shows every part and number that could be on a particular carb. In the case of the WT-3 there is no choke built into the carb as the parts listing for the WT-3 will show. The second line item in the description on the diagram shows the venturi in mm. The choke go-verticle refers to sounds like it is mounted to the air cleaner or something and it just rotates and is not actually part of the carb. If that is the case remember you won't use the airbox when in the plane.

Unfortunatley there is no information available anywhere from Walbro showing the numbers cast into the intake side of the carbs. The carbs I have have numbers from 18 to 42 and run like this: 18, 20, 24, 28, 32, 34.... A rule of thumb I have developed in my experience says to multiply the intake number by 2.5 and then round the decimal to the next highest even number. It is right on the money to the number in 64ths that is in the casting. An example may help. My WT-439 has a venturi of 12.7 mm, so 12.7 X 2.5 = 31.75 and rounds to 32. The exact number that is cast into the carb. Works with every one I have.

http://wem.walbro.com/walbro/product...num=WT%2D3%2D1

The link below is for the WT-731 which is not in the book but on the web. This is a 10.5 mm carb. This one also has no choke.

http://wem.walbro.com/walbro/product...32-1&Series=WT

Enjoy the links and look around the pages from Walbro.

As for props I would think nothing less than a 16/6 or 8 to start. Like I said some time ago, the Poulan 42 I did worked best with a MA 18/8. It turned 8000RPM.

Good luck and have fun.

Tim

RE: 1st conversion, tips and help?
 

Thank you all for your great input, comments,specs, and expertese! All the valuable information is being put to work! Just wanted to say how grateful I am and how nice it is to have a place to come to maybe help or be helped by other rc enthusiasts. Thanks! Al

RE: 1st conversion, tips and help?
 

No problem at all. Not everyone can pop big bucks for a DA, BME etc. There really are no secrets to these engines and nobody minds sharing the knowledge or experience. Funny thing is I had to buy a DA 100 as there are no twins to convert, yet they thought it necessary to grind off all the numbers on the carb. Now how are we to know what carb rebuild kit to buy if needed? Not like we can't figure out what it is. What are they hiding? They didn't invent the carb. Good luck.