Homelite 26cc gas engine conversion

[sierra_bravo]

Well I was looking in my shed for some metal rods for a landing gear and in a corner of the shed I see a gas Home-lite leaf blower with a 26CC engine. I didn't test the engine because the only thing going threw my head was "well got to take this engine out of it's plastic cage" and so I did pull it out and cleaned it up a bit and also repainted the muffler but I dont know if it will run. I tested the spark plug and it does work. The rubber part of the primer bulb broke so I know I have to replace that and was thinking about this kit to replace the bulb and some of the fuel line. The carburetor will open and close smoothly but I dont think it will work for a RC engine. I dont know alot about small gas engines but I am pretty sure the piston has compression. The gasket for the crank shaft has to be replaced and the spinning part (which I think is called the fly wheel) spins smoothly. My goal with engine is to get it working to put in a SPAD 1/5 scale piper J-3 cub and to take it to a AMA event at my field. The event is August 15th which gives me around 50 days to get the motor running, build the plane, and get it to fly.



So since I'm 13 and dont have alot of experience(nor money)with gas engines I need some help on what I should do to get this motor running. My first question is how can I test if the engine will run. Should I just reconnect the fuel tank fill it with some gas and try it that way or it there some other way.

Thanks
-sam

 

[Team_Monkey]

Sam,
First off I salute a dude digging in to make something from scratch. You'll find that 26cc engine more difficult than some to use as a conversion engine. the back plate is angled IIRC which makes mounting difficult. Also the carb base is an odd thing. I had one of those and recycled it because t wasn't as convertible.

Check craigslist for an older Homelite 25cc or a Ryobi 31cc. Craftsman trimmers are usually Ryobi engines. Homelite 33cc and 45cc chainsaws are also easy to convert and run amazing! Many have converted those engines and can help you through, I'm partial to Homelite conversions and have a few. One thing you did hit on was the carburetor. You will find that to be the most expensive part of a conversion. Prices have jumped horribly in the last few years and you could pay $30-$45 for the right unit.

For the best info on converting commercial engines to radio control use, check out the conversion forum on RCU.

If you were a bit closer I'd get you an engine from my box of donors.

 

[Team_Monkey]

Oh and a converted 25cc engine will power that cub nicely. I have a converted, mostly stock except the carb, 25cc homelite that flew a 12.5#, 72" span sport flying SPAD nicely.

 

[sierra_bravo]

I had a feeling you were going to respond first team monkey. I did notice that the back plate was at a weird angle. I was looking at different ways of mounting the motor and I was thinking about attaching bars to the 4 holes that are more towards the front of the motor next to the fly wheel. I'll post a photo below with the location of the mounting holes. The only problem is that it would be wide since it is besides the fly wheel. I'll check on Craigslist to see if there is something that could work and that's cheap. I wont be able to start buying any of the parts until Monday at the latest but I will work on some ideas on how to mount the engine to a firewall and also how to attach a prop to the crankshaft. Also I have to test the motor and I think that the best way would be to connect the fuel tank after I fix the primer bulb and see if I can start it that way.

Oh and I have to fix the gaskets for the carburetor and the back plate so I probably buy some of this to get a good seal. I called a sign shop and asked them how much it would cost to buy just two sheets(even though I need four) 4'x8' sheets pof coroplast and they told me $100 which I think is to much but I may be wrong. Also I wanted to know how thick the coroplast I get should be? I would think 4mm for the whole plane but I may be wrong.

I was thinking of replicating this scale cub
but modifying it to have a 85" wing span and a 54" fuselage with a two part wing and an aluminum spar


But that is all to come(hopefully soon). For know I'll get to thinking of ways to mount the engine to the fire wall.



Thanks
-Sam

 

[sierra_bravo]

Also I took the carb off to inspect it some more and found that the diaphragm is in good shape and that it does have low and high speed adjustments. I still dont know how I could attach a servo to control throttle.

 

[sierra_bravo]

Man never thought gettins cheap 48"x96" coroplast sheets was this hard. Where does everyone get there coroplast from? I'm still trying find someone who sells it for a good price.
-sam

 

[Team_Monkey]

I have seen one of those engines done on RCU and the dude bent some 3/4"W x 1/8" thick AL barstock to mount the angled back plate to a square firewall. Once you drill out the caps on the carb I will bet you a nickle you find the needles are not adjustable. I hope they work, but manufacturer's had to make changes to meet the changes in the EPA concerning commodity engines.

I buy corplast straight from Harbor Sales. Prices range from $10 a sheet to $15 depending on their stock. It can be shipped in 4'x 8' sheets ($$$) but most folks order it in 2'x4' (or 4'x2') pieces. If you do order from them, call them to be sure you, and they, understand which way the flutes are to run in your pieces.

As for thickness, I build mostly using 2mm but for gassers I'll do a 4mm fuse and sometimes and combo 4mm/2mm wing. It's called a red neck airforce style (RNAF) but I don't know why. That plane above is a 72" x 16" symmetrical 2mm wing with 4mm ailerons.

If you're going to work in coroplast you should check out spadworld.net. I've been sharing information over here but one cannot duplicate all the progress we have made in coroplast designs and crafting in a few posts on a new forum.

Check out the pictures in that folder of the plane above. You'll see how I added a servo horn to the carb to connect the pushrod and not have metal to metal contact. Also, it's not as much an issue with 2.4GHz radios, but make sure you have an RCJ8Y plug, or any plug with a resistor in it or you will have radio issues.

 

[sierra_bravo]

Thanks for recommending the website. I'll call them later to ask them about pricing and ordering. I would need 2 4mm 4'x8' for the fuse and other parts and 2 2mm 4'x8' for the wing covering and if they have some in yellow that would be better. I did think about making a plate that bolted onto the rear plate of the motor that would have beams that bolt onto the firewall so that would be more square. Also when you said "Once you drill out the caps on the carb" what did you mean by that and how could I see if the needles are or aren't adjustable. If they aren't adjustable then should I just change the carb.

Thanks
-sam:cool

 

[sierra_bravo]

I looked at photos of your carb with throttle control then looked at mine thinking of a way to attach a push rod but because the way the carb opens and closes by rotating a rod and because of the way the rod is facing I think that I wont be able to setup a throttle control with this carb. I doubt that I would be able to buy a carb from a RC gas motor and stick that onto this motor so is there any other option.

Also I never posted photos of the engine so here they are.

 

[sierra_bravo]

Oh my gosh $300 to ship four sheets for 4'x8' coroplast. I almost got a heart attack but then I remembered that they are 8' sheets of plastic so I told them to cut it into 8 2'x4' sheets and it ended up costing $35 shipped . I am still going to call home depot and some other hardware stores to see if they have coroplast. Also can I glue/tape two sheets of coroplast next to each other to make a longer piece for the wing and fuselage.

thanks
-sam

 

[Team_Monkey]

You really need to grab a soda and take a few hours to look at how we build big planes. There are years of examples of what you want to do. Threads devoted to where to buy materials and so-on. There is a small chance of getting 4mm coroplast at any big box store but you can check. I have a friend that lives in northern South Carolina that builds SPADs. I'll ask him where he buys coro.

If you do buy from Harbor, remember that the second dimension you give them is the direction of the flutes.

Also, take some time to read through threads over on the RCU conversion forum about Homelite engines. I think you'll see that engine might be more trouble. You need a roughly 9mm carb to get a 25 breathing decent enough to be a plane engine. The stock units are 7mm or 7.5mm. There is a whole list of possible replacement carb's in a thread over there.

 

[sierra_bravo]

Yeah your right. I ignored both the SPADS fourm and RCU engine conversion fourm for some reason knowing that they are both stuffed with so much info and knowledge. If you didnt contact your friend I appreciate it alot but dont. I found some coroplast at my local home depot and i'll just paint it yellow if i don't buy some from harbor sales.
Thanks Monkey for all the help and advice i really appreciate it alot.

Well im off to the RCU and SPAD forums.

Thanks

-Sam

 

[sierra_bravo]

So after reading alot on the other forums mostly about this motor i decided that this motor is bad for converting and I should find a homelite 25cc motor. I should of have listened to you Monkey when you said these motors aren't good for converting. I haven't given up on this project just a slight road bump. Well I better start looking on Craigs list and some other hardware stores.

-sam


EDIT:
If I cant find a good used weed eater then I was thinking of buying a new one knowing that it works. I was thinking of this one

 

[roversgonemad]

Good stuff. I know there's a Ryobi motor that is very popular for conversions. Do some searching and you'll probably find it. Monkey probably know which one it is.

Looks like it's the 31cc model. There's lots of info out there on the Ryobi conversion. Here's one of many videos with info.

 

[Team_Monkey]

Honestly, if it wasn't for me already having a box of engines I would just buy a true R/C engine. The prices have come down and the quality has gone up in the "off-brands". Especially don't go buy a new trimmer or saw for the engine. You will end up with more money in an OK, heavy engine rather than a purpose built one with electronic ignition. I know a few guys that have had good luck with the 52cc $175 Turnigy engine. I see the 30cc is only $145. I think the parts for my first full conversion cost that much! LOL
Converted 33cc Homelite saw on the nose of a 1/5 scale FW-190.


Still, if you can find a decent, older 25cc homelite trimmer on craigslist (I just found one for $20 on a search here) you can convert those cheaply. I can help you with how to do a home made engine mount plate, home made prop adapter and a carb stack. Also, if you need a bit more power and have the time there are easy things that can be done at home to liven them up.

Also, O.S. now makes a gas "glow" plug that lets you remove the ignition setup to save weight. I have a Featherlight 15cc that I plan to convert this summer for a MKII 60 size fun fly SPAD.
The original RIP, loved this plane, killed by a dead Rx battery.


Oh, if you plan to build it out of all 4mm it will be heavy and a 25cc might barely fly it. If going heavy you might want to keep an eye out for a 31cc Ryobi or a 33cc Homelite saw. Either of those will happily turn an 18x8 prop.

 

[sierra_bravo]

Yeah I looked at turnigy gas engines and alot of people say that because the QC isnt very good you might get a somewhat working one but you might not. I talked to av8tor1977 from the RCU forum and he told me that he had a 30cc homelite engine in good condition that he could sell me for $45 before shipping and I sent him a offer for $35 but I am waiting to see what he says. I was think of buying some of the parts like a muffler to convert the engine from JAG engines because I don't have a lathe to make the parts myself but I might still be able to make some parts like the prop adapter and engine mount plate and if I can then I would really appreciate any help I can get. Also if I do get the O.S. Glow G5 Gas/Plug does that mean I dont need the flywheel with the magnet and the ignition coil. If I dont need those things then how would I start the engine. I wasn't planing on using 4mm coroplast on the wing just 2mm. I would use 4mm on the fuselage unless I could also use 2mm to save weight.


Thanks
-sam


Oh and I updated the order for the coroplast from harbor sales and the total came out to be $50 for 8 4mm 2'x4' sheets and 4 2mm 2'x4' sheets in yellow. I also found these sheets of coroplast at home depot but they are all 4mm so I could really only use those sheets for the fuse.

 

[Team_Monkey]

Both guys I know with those Turnigy engines are very pleased with them. Both are (or were) on UltraSpadSticks
Any converted engine you get from av8tor will be top notch and totally worth the $45, it's especially a steal at that price if he has a new carb on it.

IMHO, Ryobi engines are tricky to mount because of the rear carb. Homelite weedies are easy to mount because of the flat back plate and side carb but they are small at 25/30cc. Of course the side carb makes them hard to fit in a cowl, but on a cub you might be able to fit it in a dummy engine "bump" on the cowl.

The muffler isn't hard to lighten and modify if you have a welder or a welding shop close by. I messed my first one up and the local shop fixed it for $10. For these small, low power engines, you can make your own prop adapter using hardware from a good hardware store (not depot or lowes). You do need a welder for that too but at least not a lathe. I have also seen guys cut down a flywheel and just bolt the prop onto that using a nut on the crankshaft, no adapter. I plan to do that with the little 15cc Featherlight, although I may have to run a die down the shaft farther to get enough threads.

Yes, you remove the flywheel and ignition coil if using the OS plug. You use a regular glow igniter to start a gas engine and then remove it after it is running. A dude over on spadworld tested it on a conversion engine and it ran fine. I don't know if it makes the same amount of power as an engine with a spark ignition but it is super easy and can save over a pound on most engines.

 

[sierra_bravo]

av8tor responded saying that I could have the engine for $55 shipped and he will even send me a backplate mount. He said that the motor has no damage also that the piston and cylinder are in very good shape. So I have( or will have after I pay for it and he ships it) the engine. I don't have a welder but my brother does so I can ask him if he could weld some stuff for me. As for the prop adapter what hardware would I need or do you know of a forum post on how to make prop adapter. Also If can remove the spark plug, ignition coil, AND the flywheel which weighs a ton and replace that with the OS plug and just use a glow plug starter then I'll do that before I do anything else on the motor.

Thanks
-sam


UPDATE:
so before I posted this av8tor1977 send me a PM saying that he also had a carb that he could through in which is awesome.

 

[Team_Monkey]

av8tor is a great guy over there and is full of great info and experience. I am prepping (2) 25cc engines for a large build and will use his non-machine shop upgrades for porting on the little homies. Search for "homelite down on power" in the conversion forum on RCU and you'll find it.

I meant to do some more work last night but ended up running some missions on Destiny.

The fast prop adapter description is in this thread. Note that it is only for lower power engines (not saws) and has to be welded.

 

[sierra_bravo]

Thanks for the link. I'll be using that prop adapter since it looks pretty simple to make and uses very few parts. The 30cc motor doesn't have a lot of thread on the crank shaft so I'm not how well it will work but then again I don't think that would affect it very much since it is going to be welded. Well I guess I have to wait for the motor to get here so I get any work done on it. I am still looking for some plans for the plane but I cant find any plans for a 1/5 scale cub that could work but I do have some schematics for the full scale cub so I'll just base my plane off of the full scale plans.

-sam