Finally got around to finishing my Stihl 62cc out of an 036 chainsaw. It was a bit of a labor intensive conversion, but it turned out nice. Turns a Zoar 22 x 8 prop at 7400 rpms.

I had to make an intake manifold adapter to fit the oddball round intake port. My first idea was to use a homemade aluminum adapter, along with a spacer that used the carb mounting bolts. I was going to insulate the bolts themselves with shrink tubing, and use fiber washers under the heads at the carb, all to insulate it from heat. This didn't end up working too well, as the carb still got too hot. Also, that setup was too long to fit the cowl of my 28% Wild Hare Extra. So I milled down my aluminum adapter, and made a new insulator that bolted to the adapter, and had separate holes in it to mount the carb, thus properly insulating the carb. That setup works perfectly.

Of course cutting the engine out of the saw was a bit of a chore, but it really doesn't take too long when you get right down to it. Just be careful with those magnesium shavings and grindings....

I didn't want to use the tapered end of the crank, because it had a very small threaded end that I didn't trust to screw a prop adapter to. So I cut the other end of the crankshaft to length, then bored and tapped it for a stud. The prop adapter screws onto that stud, and seats against the shoulder where the stud screws into the crankshaft. The prop adapter extends back over the crankshaft in that area, and is also supported by radially placed set screws. The crank is a real "bear" to work with, as it is super, super hard. Anyway, I then cut the tapered end of the crank off right at the bearing, and made a plug for that end of the crankcase.

Instead of using the original screws to hold the crankcase halves together, I made up studs. The aluminum mounting stand offs are tapped, and screw onto those studs, thus holding the crankcase halves together. The standoffs are also machined to be a snug fit into the counter bores of the crankcase half, thus increasing their security even more. Extensive test bench running showed the mounting system to be stable and problem free.

It weighs 4 lbs. 8 ounces complete as shown, and handles very nicely. No porting was necessary as I checked the port timings and found them to be quite adequate. So, it is a bit lighter than a Zenoah G-62 Lite, and makes more power too. But it wasn't a "slam dunk easy" conversion.....

AV8TOR

Well, I thought it made for an interesting post. Seems like this part of the forum, (and hobby??), is dying.... []

AV8TOR

It is interesting, but so few have the machine tools and the knowledge to do this. Every body wants bolt on.
That was a PIA when I designed stuff for CH. " What do you mean I have to drill and tap a hole?"
AND there is always some new super good deal Chinese engine out there.

Yeah, I think the Chinese engine is what hurts things the most. It's killing my converted engine sales too. Personally, I would rather have a high quality Japanese engine that I can get parts for almost anywhere than any Chinese engine, but as you say, a lot of people have to have the newest and most "plug and play" item out there, even if it is inferior quality and questionable service....

AV8TOR

I somehow didn't see it, interesting build definitely, I've just been too busy with life to fly let alone convert engines (my lathe hasn't even been at my house for about 6 months, work needed to borrow it).

I'm glad your 3 standoffs set up like that are working good, I have a similar setup on my old Pioneer 52cc with 4 standoff's that I don't have all that much run time on that I've wondered about at times, hoping to get that plane up in the air later this month if things cooperate.

I have more fun converting the engines than spending money on one, sometimes you find a diamond in the rough, sure it might take some experimenting to get there but you usually get there.

Things need to stop breaking for me, if it was small things it would be one thing, but when your daily driver breaks down and the backup vehicle (at the same time) it puts a damper on anything fun that you want to do.

I thought your post was very interesting. Though I have never been a converter myself, the interest has always been there! I no longer own or have access to the necessary equipment so I probably won't be getting into converting anytime soon. I do maintain a couple of Stihl saws and spent more than a few hours on the back end of one last weekend after a windstorm went through our MN lake property! I've always wondered how they would be as an airplane engine!

I did note you used the original Stihl carb and that the cylinder was of Mahle mfgr. You noted cylinder timing ..... how does the Stihl cylinder compare to a typical model engine's timing? Keep up the good work ..... the posts are interesting for sure.

Real nice work on the Stihl conversion there.

I've worked with stihl saws every day of my working life and often wondered if the de-compression valve would be of any help in our modeling instalations ?


My gut felling is no, but still curious.....or should that be 'stihl curious'

                                Take it easy
                                            john

No..............

+1

AV8TOR

I've misplaced my notes.... The exhaust I remember was around 158 degrees, which is fine. I remember thinking the intake timing was a touch high at about 150 degrees. If you do one and have room for it, a velocity stack would help with the carb reversion.... But mine handles well even though just a touch rough at idle.

AV8TOR

Do you still make the carburator and prop adapters like the ones shown in your photos?

For the following engine:
http://www.ebay.com/itm/46mm-Cylinde...0AAOSwT5tWO9io

I will send you a PM when I get my PC back up and running, which I hope will be shortly. It is a PITA to type on this little Kindle I am using right now.

AV8TOR

Please, to me also. I have eyeing that cylinder/piston/crank/case offering and wondering what it would take to make it into a usable AC engine. Thanks.

Hey Guys,
I have 2 of those motors. Lot of work to convert but well worth it. The oldest one came out of a 039 chain saw. The newest one, I purchased the short block from Baileys in California for $99.00. They have a massive crankshaft.
You really need to have access to a machine shop to do a serious conversion. The carburator is the
biggest problem because of the unusual intake design. I'm going to offer for free the Auto-Cad drawing I made up of all the parts. It's a .dwg file and should open up in draft sight. I also had lots of pictures but I'm not sure where I saved them.
Send me a real E=mail if your intrested. [email protected]
Thanks,
Larry Kopecky
Conyers, Georgia 30094

Guys, by the time you have a suitable intake manifold and prop adapter machined, make provisions for CDI ignition and adjustable timing, engineer and make a mounting setup, and buy a carb, muffler and ignition, you will have some bucks invested in the engine, and it still is a Chinese engine. I have Kawasaki and Echo engines in that size range I can convert for you. They are better engines, with known reliability and great power, and are easier by far to mount. The price for them completely rebuilt, converted, and test run would be close to what you would have invested in the engine we are talking about, but it would be genuine Japanese high quality. I know that "first rattle out of the box" the engine and its price look attractive, but when you look at the big picture, things change.

If anyone does one of these, please remember to make whatever carb mounting you come up with completely isolate the carb so it can't heat soak. I ran into that problem. Trying to tune a carb that is too hot will drive you nuts and you could even ruin the engine with a lean run. Hot restarts will be a problem as well...

AV8TOR

Thank you AV8TOR. Your candid discussion of the pros and cons of this conversion has left me wanting instead to come to you for engines of this type. The quality of your work on industrial engines of known reliability, quality, life and power output is evidenced by the many happy users of your engines.. Thank you very much, your contributions to this hobby are well appreciated by me.

Sincerely, Richard

Thanks for your reply AV8TOR, I have thought about the big picture a lot, IMHO the converted engine should last a lot longer given that it's designed for worst working conditions than for just a little flying around and parts should be available long after the chinese engines of today are gone or the companies making them go out of business, the reason I'm looking into this in the first place. Please send me the information on the engines you can convert in that size range, you can send the information to [email protected] or pm here. Once again thanks.

Thanks guys, I appreciate the kind words. I try to help people out; I think that is part of what this hobby is all about. If I charged by the hour for the engines I do, I wouldn't be even making minimum wage, but I enjoy getting you guys in the air with a good engine.

Let me go through my engines, and see what I have to offer, and I will get back to you. I had a major back surgery last July that really put me down, and now, I recently found out I need another major back surgery. But I will have time to get a couple of engines done before hand if you guys want them. I'll be in touch shortly.

Thanks again,
AV8TOR