i have heard of a few people doing these conversions from chainsaw or weed whacker engines onto their planes. cant help but wonder if there is any advantage to this what are the pros and cons of this and what are the best ones to use. Also how are they done? wouldnt the prop hub be difficult?

Pros and cons?
There are many of each

Pros
This is a hobby, Some get their major enjoyment from flying ready built planes, others get their enjoyment from building airframes, others get enjoyment fom "messing with engines". Conversions can feed the needs of those who like to "do stuff".

The basic engines can be obtained very cheaply. and it really only takes a little time, some basic machining and you have your finished product that you can say "I did it".

Cons
Takes up time so it removes the "Instant gratification" that some feel the need for.
If you have to pay full price for the machining to be done, it is not a cheap excercise.

Echo and Sachs engines seem to be the number one choices for conversions for the companies that specialise in doing the conversions on a semi commercial basis. Many other brands are commonly used such as Sachs, Poulan and Ryobi.

There is a whole Engine conversions forum here where the search function will show you many ideas.

one of the cons is generally lesser performance and higher weight than most hobby grade engines but to many like myself that would rather build their own engine or don't have near enough money to put together a "typical gasser".

On my Ultra Stick Lite 120 I have a 32cc McCulloch weedeater engine converted, including ignition I have about $75 into it. I do all of my own machining so that makes things cheaper. To account for the lesser performance of the weedeater engines I did some port work and gained some performance back.

Chain saw engines in general have better performance of the utility engines, but Stihl and Echo are high quality and good performers on any of their engines.

Like aussiesteve said, the machining is fairly basic, most modifications can be done with a hack saw, pliers, screwdrivers and files. The prop adapter is the most complex part but for some engines all it is is a fancy looking spacer. When I'm making them I make them about the diameter of the hub of an average prop for that size engine and shape them to what I think they should look like. The only thing I actually measure with a caliper is the size of the drill bit for the center hole, or if I'm making one for electric ignition figuring out the taper of the crankshaft can be interesting...

After converting a half dozen or so weed whacker engines, I have also modified or rebuilt conventional model engines both glow and gasoline and made some from parts of several crashed engines. I have also converted glow engines to use gasoline.

There's no end to what you can do.

It is easy if you have experience doing conversions. If you do not have machine shops skills it will be a challenge, probably not doable. Prop hubs are an exersize in precission machining, they are very frustrating to get right. Some engines are easier than others. The Echo 50cc chainsaw is very easy, especially if you buy all the parts you need from an outfit like berelli customs. You end up wiht a clone of the BME-50. It is a respected engine. On the smaller side the Echo 21cc weed wacker makes a very nice engine with minimal work. It converted and sold as an airplane engine on a comercial basis.

Most of the modern crop of wackers are not as good as the old ones for conversion purposes.

It is mostly about the process of doing somehting for yourself. It is like building airplane kits, tieing fishing flies, and a lot of other hobbies; you could probably buy the item you made for less money in the end. If you are already tooled up and have material on hand it is seems much cheaper because you forgot about what you spent on materials and tools. No matter, it is fun. I loke to tinker in the shop. It is a hobby I do to unwind. In the end I have something cool that I can admire an use. I am the only one at my club that "makes" engines. I get a lot of compliments and interest in my engines. The engines and the planes I make are great converstion starters.

If it is about getting in the air, with the least fuss, get an ARF and a ready made engine.

i got a Stihl trimmer today. it is an FS36 looks pretty good to me and was just wondering if anyone had done a conversion on one of these yet, im sure it has been done.

sounds like it ends up being like a Ryobi 31 with a couple little differences from my quick search

For me, converting engines opened up a whole new exciting aspect to the hobby in general, and I have engines that I could never afford to buy commercially!!

AV8TOR

exactly, I couldn't afford a $400 engine, it's hard enough for me to spend $400 on an ARF and radio stuff... people are always impressed when I tell them my ultra stick is powered by a weedeater.

Does your FS36 have a light colored tan backplate with a reed valve (Carburator attaches to) and a long propeller shaft. If so, it is indeed a RYOBI built unit. The tan back plate offers some advantages. The carburator is a quarter turn from the regular BLACK back plate, and a little longer. All parts are interchangeable such as black back plates ect. Good luck. Any questions, I am glad to share my experiences... FLATHEAD

Thanks for the offer Flathead. I haven't gotten the casing off the trimmer yet but when I do in the next couple weeks I will let you know. Any advise you have for this conversion before I get started?

Check out the Farmers exchange for echo short blocks. You can choose your desired size And there are parts on the net for convercions.

farmex.now.TC