I bought a 15.9cc toro engine from a fellow on rcu. Where is best to shop for a carb, muffler etc. I can measure the bolt patterns. I just have a hard time figuring out metric bolt and screw sizes.

I never did a Toro, but it should be similar to a Ryobi. First you strip off all the weedwacker stuff. You shouldn't have to change the carb, if you do it's probably not worth the effort, you just want to get do to as close to a model airplane engine look as you can. It probably has a magneto, and a pick up coil on the front, most guys turn the extra fins on the mag off in a lathe, then make a prop drive that fits over the end of the crankshaft so you can mount the prop. You might have to buy an after market muffler, but try to use the stock one.

I've converted 3 Ryobi motors, the first I used the mag, the next two I added IE, you want the IE, for $100 I have a 31cc motor that turns a MA 16x10 7300 rpm, idles at 1600rpm, hand flip starts.

2 Ryobi power heads for $13.50 each off eBay, and IE for $85.00 from http://lsproengines.com/lspro_012.htm

there was no carb. just a block of brown plastic. must have been gravity fed with no needle adjustments

small enginea all use thw walbro type, which have standard block dimensions. Take any one that has a venturi number of about 18 to 22 . (garden appliance stores) #22 is 22/64th of an inch. For 16cc that would be in the smallest walbro range.
The number is visible when you look down the throat of the carb.

I found the carb in the packing material. I took it apart to see how the cable attaches and the little bent spring clip went orbital. I still may have to get a carb if I can't find a spring

I contacted Isproengines about the ei ignition. They responded but did not know the answer to my question which was "How do you attach or integrate the ei ignition with the original toro magneto". Do I leave the flywheel with its magnets and get their "Hall sensor" to create the connection? and if so, how do you determine where to mount the sensor? It would be nice to remove that huge magneto. it seems to weigh as much as the engine. My local hs has a small lathe that I hope can be used to turn the back fins and junk off the flywheel. at the same time can I thin the flywheel main body and magnets to decrease weight? My us35 has a big flywheel with fins like the toro. My SPE40 has the little pickup and a magnet about .160 dia. in the back flange of the prop hub. B&B is making me a prop hub to go inside the flywheel and threaded to hold the fly wheel on. They are also sending me a walbro carb and a muffler to fit. From what I have read leaving the flywheel will help the engine run smoother at idle. I will admit the spe shakes like a wet dog at idle but smoothes out with a little throttle.

No, that's one of the plus' of the EI you get to loose the mag/flywheel.

If you can get B&B to just make the prop hub with the magnet in it and a little longer to make up for the mag/flywheel being left off.

On my Ryobi conversions I took the mag/flywheel off, put a 3/8" hole the length of a piece of 1 inch aluminum stock, made a small forcing cone at the back of the prop drive and put a slot for the woodruff key, drilled a hole to accept the button magnet for the hall effect, then peened the mag in. The first conversions I drilled 4-40 holes (#29), then taped them, but now I just scuff the front of the motor and use a hose clamp to hold the Hall effect sensor on the engine. I timed them so the back edge of the magnet was about 3/8" from the sensor at TDC, then fine tune the timing while it's running.

This all sound hard, but it's quick and easy to do, and you end up with a much better engine.

I think that when you remove the flywheel the engine will shake more at idle, but they smoothen out as you increase the rpms.

I will have to contact Mr. Bennett and see if he can make the prop hub with a magnet in it. On the front of the engine there are 8mm threads for the nut/hub and then the shaft tapers larger with a key way. Where do you find a magnet to install in the prop hub? I'm afraid this is getting way over my head. By the time I get all this custom work done I could have probably bought a 20cc engine. I am trying this 15.9 for my 60-90 sized corsair. it should be about the equal of a 1.08 2 stroke.

I got the little button magnets from my daughter, the came out of a toy that uses two in a plastic strut to connect steel ballbearings together you get about a hundred struts a fifty ballbearings in the toy, they where recalled for loose magnets being swallowed by kids, then they needed surgery to get the magnets out. If you need one PM me and I'll send you one.

Just make your engine look like your spe.Heres a pic of my echo 24cc and my stihl 28cc.just copy them.I make my own prop hubs now.The mufflers i bought from lambertsrc or i just gut the stock one.I did a toro muffler and it only took about 5-10 minutes total time to take apart,gut,and put back together.No brazing,welding,soldering or anything.Just unbend the edge,gut,then put back together and flatten edge with hammer.