Just picked up one of these chain saws for $99. brand new at Home Depot. I haven't taken it apart yet so can anyone tell me who manufactures this 40cc engine? I would like to convert it so any additional info. is welcome. Thanks for your consideration.

I have a Poulan 42cc on my Giant Big Stik. It pulls it straight up after about a 20' take off roll. I believe the plane weighs about 13.5 lbs.

I think the 40cc is of the same design as I also have a Poulan 36cc that looks identical to my 42cc. If it is like mine, it is very easy to convert, but you will need to either put electronic ignition on it, or use it as Gas/Glow like I did mine. The ignition parts are in the saw body; not mounted to the engine. One thing I do like about it is that unlike the commonly converted 46cc model, you don't have to make some sort of a carburetor mount. The carb mounts on a phenolic spacer like most engines.

The pics shows how I mounted mine and I have had no problems with it after a year of flying, but it is more common to make aluminum side plates that bolt to the crankcase bolts, and then bolt to a standard beam mount.

AV8TOR

AV8TOR, Thanks for the reply. What are you using for a prop hub, muffler and do you know which Walbro carb is on it? Also, does CH make an ignition for it?

Hi,

The cheapest way would be to make your own prop hub, and gut the stock muffler and add two large outlets like I did. However, the answer is yes, CH Ignitions does make kits to convert them.

Here's a link: http://www.ch-ignitions.com/newstuff.html

Note that the 33cc stuff works on the 40, and you don't need the carb adapter shown for the 46cc engine. It would be best to call Terry at CH with your needs. They now have a cheaper ignition system available too.

As far as the carb, I'm running one with a 13.5 mm venturi. Your stock one will probably work fine. The chain saw engines don't tend to be undercarbureted like the smaller string trimmer engines.

AV8TOR

I bought the same engine. Did your engine have a strange carb set up with an extra air intake above the actual carb with a butterfly valve? I was going to make a different plate to mount everything but i'm now thinking if it fits under my cowl i'm just going to leave it the way it is?? are all chainsaws engines like this? this is my first chainsaw conversion.

Monster, I don't know. The engine is still in the chainsaw. I won't do the conversion for awhile.

Any Ideas where to start for prop sizes on this engine? Its going on a 80" Cap 232.

I like an APC 18 x 8 on my 42cc, but then I run my engines at higher revs than a lot of people, and I don't fly any 3D. Most people would probably run a 20 x 8 I would guess...

AV8TOR

I've got my engine on the test bench and running on the glow plug. i'm running it on 1 part nitro 2 parts gasoline. with a 20x6 prop i was getting 6900rpm. Which was pretty good, it is just over 20lbs of the thrust but only about 40mph, is that enough speed or should i look for a different prop. also i switched out the zama carb for a walbro 38B carb off of a stihl weed wacker, for ease of tuning and it did make it alot easier to get running and keep running.
The engine ran all the tests and idle without any glow plug driver. I am still amazed how easy it was to convert.

Hi,

A lot of guys prefer the larger prop and lower rpms. More static thrust and less speed. I don't fly 3D however, and prefer more speed. I also like the ability to cruise around at half throttle, with power in reserve when I do maneuvers. I used an APC 18 x 8 on mine, and the 42cc turned it at around 8400 rpms. I flew the engine for a year in this manner, so it shouldn't be a problem. If you are going to put the engine in something sleek and fast like a warbird, the engine would easily pull an 18 x 10 prop.

AV8TOR

AV8TOR
Thanks for the help. are you running the original zama carb? whats your ignition set up? Did your engine have an additional air intake above the carb?

Hi,

I was running it on Gas/Glow, and I had a Walbro carb on it. I have had some troubles with Zama carbs not "liking" the Gas/Glow mix, and distorting diaphragms. Never had that problem with numerous Walbro carbs. No, mine did not have that extra intake.

The engine worked great, and the only reason I took it off the airplane is because I wanted to try out my new twin. (Also on Gas/Glow)

AV8TOR

whats your glow gas mix? we tested at 2:1 gas to glow. It could be that my carb is 2 small for this engine. but i couldn't get it running on the zama carb. it starts easily with the walbro.

I use the mix that we came up with, and that I recommend to everyone. It's 1 part of 10% oil, 10% nitro glow fuel to 2 parts of High Test gasoline. I have 5 engines running on this mix and have been using it for well over a year now.

If you can't get a particular carb to richen up quite enough on Gas/Glow, remove the regulator cover and diaphragm, and raise the metering lever just a touch, maybe .010 to .015" at a time. Most carbs will flow enough, but on one or two I've done I have had to raise the metering lever a touch to get a rich enough mixture without having the needles screwed way out.

Have fun, and welcome to "Gas/Glow"!
AV8TOR

Just for a follow up I have just about got my cap 232 done. we did some actual thrust test with a digital fish scale. 20x6 prop at 7300 we were getting a consistant 19lbs. which should do fine in a 15-16 lbs. I would like to test some other props out but at $20 a pop i think i will just get this plane flying before i spend anymore money.

What brand of prop are you running now?

Dynathrust