i have just recieved a 50cc two stroke strimmer engine from a mate of mine at the club.

i intend to convert it to turn a prop and use on a large aerobatic model.

because these engines are so heavy, is the general idea to lighten them as much as possible, only keep the necessary material for the engine to function and remove the rest?

i am currently removing the flywheel housing, it serves no purpose other than to hold the magneto, so i am leaving the mounting point for the magneto.

at the back of the engine was a threaded shaft for the recoil start, i think i should remove this shaft as it servos no purpose, i shall be hand flicking it anyways.

what is the best way of mounting these engines, at the back of the engines is 4 threaded holes where the recoil start used to be mounted, do i use these or mill them away and use a different method?

thanks everyone

Before you get too far along, you need to determine if the engine has needle bearings or ball bearings for the main bearings on the crank. Needle bearing engines are not usable for model purposes because they lack the ability to handle the thrust loads imparted by the prop.

The rest of your assumptions are correct. However, I doubt you will be able to flip the prop fast enough to produce a strong enough spark to start the engine. You will have to use a electric starter.

Good luck,

Jim

Sorry to disagree but Quadra 35-42s. US engines use needle roller brgs. Quadra uses a brass thrust washer. US uses none.

You can also replace the front needle bearing. Usually the case where the bearing is has enough room to put it in a lathe and turn out the bearing area to allow a 32mm ball bearing. I have done this on a couple of engines ratha than throw them away.