Do I NEED a windowed piston in order to use a reed valve?

Absolutely you need a windowed piston if you want your reed valve to work properly. The only time you wouldn't need a windowed piston is if you are using a case reed. The piston is bypassed with a case reed and I don't think you would need a windowed piston in that case. Here is a pic of a case reed.
 

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Considering these engines are old school Schnuerle ported and have a full wheel crank I'm not surprised that reeds seem to be very important.

It's funny that most commercially sold, piston ported 2 strokes now days still have two side transfer ports like these ( or windowed transfers..) and yet put out more power and come into their torque from lower revs. Dozens of chainsaws and even yard implelement engine make more power than these engine do stock. Why is that?
 
I have the same gt7 with the reed and the keihin carb but it did not come with à third tranfer port or à windowed piston either.

I managed to run it like that but it four stroked like 80% of the throttle range. It sounded right only on idle and from 1/10 to 2/10 throttle so i bought à jet kit and put à #70 on it to lean it à bit but it did not solve the problem.

I think i am gonna try without the reed but with the adaptator the 45° 4 bolt i dont know how to post à picture on someting else other than facebook so for now i cant show it but someday i will find the time, like buying what should have come in the kit, (some jets and a properly ported cylinder or at least à windowed piston), The site i ordered from does not have any so i'm thinking of selling it for à s***y price and buy à s***y stock China Girl so if i get screwed, at least im not going to dump à bunch of money into it.
 
Bienvenue, como va tu ?

(I corrected some of your wording in your post to a more correct form of Americanised English versus your 'Patois', (Francais Quebecois), wording which did not translate well into English, just so that it will be more understandable.)
 
You have a hole in your intake manifold that will be causing a too lean running condition on your motor...Probably due to faulty welding there...something burned right through it...DAMIEN
 
xspade17x said:
Yes the windowed piston makes an Incredible difference you also need a third transfer port. I went thru this with my yd100 with a reed valve
Click to expand...
Where do you put the 3rd transfer port. Can you show me a pic of where please.
 

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