JPG[/attachment] Here's what i did with an RT1 piston in my RT2 as skirt looked a bit weak to drill big holes lower down. Way overdone of course so Don't Go There. Worked good though. Stupid things i do at times.
I guess with yours someone was trying to help it along a bit!!. Transfers are around the side of the cylinder & boost port at the rear where those holes might help. I dunno, i'm pretty basic on porting knowledge & tend to overdo it then can't go back haha. Pic coming & one seen ya can't unsee it!!.

My experience with a similar problem after re bore and other work on my '71 CT1C. The main jet hole did not lined up with the float bowl hole. No power and lots of smoke..I bought a different carb and noticed this when I was taking them apart to build a really good one. Made a huge difference. I think the threads in the float bowl may get stretched from over torquing. Anyways I got them lined up with good gaskets,etc and it runs very strong now.
  
 

The difference between the old and new windows is not significant. The difference between windows and no windows is noticeable but not dramatic, just takes away some of the midrange punch.

I was in the same boat as you a few years ago when I picked up my 74 360. Sluggish power delivery, what little power it made was on tap from 5000-7000. Not much down low or in the middle. I found nothing mechanically wrong with it, it just didn't run great. The single best thing you can do is have a proper pipe made to generate a low-mid powerband. Porting will help, head work is a good idea for performance and reliability. A bigger carb complements the other modifications.

If you don't want to go down that rabbit hole, I wouldn't blame you, it couldn't hurt to just have the squish band corrected and maybe have the cylinder ported to make the most of the stock specs. Square off the transfer port windows, match the heights up, widen the exhaust port a bit. This won't change the character of the engine but it will increase power over stock and deliver more power and torque without requiring higher revs.

Thanks for your responce guys,i will try the above methods,i think i will have to at some point cut the back out of the exhaust,out , im not 100 percent sure theres nothing still stuck in there.Im just after stock power,and at present it will struggle to even pull top gear on standard gearing..Now i know the piston is fine,l need to know that the barrel is too,ie has it been badly tuned,before i buy another.What are the standard intake port height mesurements,from the botttom of the skirt?.

The imporant thing wwith reeds , is that you can have 360 degrees of available intake charge for wheb there is a crank case signal to draw air in , I like to have holes posioned so that at BDC there is crankcace access and all the way down on the skirt to point where the skirt finally opens the intake port and the holes then dont matter , you dont have tomake them all the way down to the point wwhere the piston is weakened . When I port these old machines I make a cse port that makes continious connection with the crankcase like a modern case reed engine .
 

The inlet of my cylinder:.(It’s a RT(2) 360 ccm)
piston with the oval holes 











 

Boost holes in the piston make very little difference. They are fine as is. If low power is a problem, then it might well be due to the exhaust being badly clogged. 

When you describe badly clogged pipe, would you be able to tell by simply blowing down the end of the pipe ? I have two pipes and they seem to ‘blow’through with no noticeable resistance

Some videos to help
youtube.com/shorts/rHVgkzT60AE?feature=share

Cut this baffle off another pipe, does wonders for calming down the bark.
youtube.com/shorts/qGv1DUbL_zw?feature=share