well sure a professinally made 200cc two stroke is quite a nasty bit of machine.
(current race engines in the 250cc class hit and surpass the 100hp line)
BUT those are perfectly timed, and absurdely precise
First.. I'd say what you would want is a dead engine to start with.
(yes.. ideally one where the conrod punched a hole under the cylinder)
or one that seized close to BDC.. I know it's just a predator, nothing special..
but since this is almost as likely to not work at all as it is to maybe at least turn over under it's own spark once or twice...
both of which more likely than a nicely ticking two stroke...
you may want to pick a dead engine to begin with.
if you have a hole in the crankcase already.. the proper idea would be a reed valve engine..
frankly that's likely the easiest option anyways and it gives you the highest chance of succeeding in regards of finding a horse power or two in the engine.
then you need to rip everything out of the insides.. and make the crankcase as small as possible internally.
Essentially weld in an airtight barrier that just allows the conrod to rotate
and free the reed valve of course.
with the reed valve in place we now have the first stage of intake solved.
the second intake stage (crankcase to combustion chamber) is way more difficult.
but since we do no longer need the push rods, their pathways at least give us enough beef to
machine
And yes that does mean you will need to machine a precise cutout from inside the cylinder bore.
Exact size and shape yet undetermined.
And on the other side you need to cut a similar hole into the cylinder wall this time for the exhaust.
(exact size and location yet to be determined)
you also would want to cut some and weld some to the piston
(to make a better transistion port)
And you want a better head.. as little volume as possible
but for now with the valves deactivated (lack of cam and pushrods) it should do
And that's the easy parts done.
In theory you can take a known to work timing chart for similar stroke length two stroke
and start dialing in the timing from there.
bad news since longer resp. earlier means more cutting on the cylinder wall..
there is no easy going back!
dialing that in is iterative and takes lots and lots of trials.
once exhaust opens too early, or transition for too long,
you throw the case in the bin and start over again.
on minor cuts weld shut, resleeve and start over
(one of the reasons two strokes like their cylinders separated from the block
)
after fiddling with the ignition timing and dialing in port sizes (for a quick and smooth transition)
you can have a running two stroke.
I doubt it has much power as of now, but if it stays running you did a great job so far.
And then it's custom fabbing an expansion chamber..
template designers for that are available.. bore stroke timing entered and
it gives you the dimensions the expantion chamber needs to be.
Oh you need a billet con rod and flywheel.
just because the rpms will have to increase a bit likely past 6k in order to generate oomph.
I reckon we talk about 700-900 dollars more if you get a custom made head.
(200-300 in parts and the rest in tools and machine time without the custom head)
finding some old 200cc two stroke on CL is much cheaper IYAM.. and bonus:
it usually comes with a gearbox and runs way better than the home made one
'sid
