Hello, I'm new to this form due to NATS forum going down or whatever happened to it. As stated in the subject I have a R5B that I'm looking to restomod a little but not heavily as I want to keep the original look but make some changes for looks and performance. I'm looking at expansion chamber pipes but don't necessarily want the upswept look or them to stand out too much. I was looking at the DG pipes or a set of Spec II. I'm also planning to bore it up some but don't know the best way to go about it. 
For a little background I am 18 and got this bike when I was 16 as it had sat in a barn since the late 80s. When I got it she was rough and I had done some work to it and got it running. My goal was to drive it my last day of senior year and while out test riding it and making sure everything was good to go a few days prior I was unaware that it was running lean and it burned a hole through the top of the piston on the left cylinder. 
Upon recently taking the bike apart since I'm planning on doing this build over winter I am led to believe it was rebuilt once before due to broken fins on the cylinders. The cylinders don't look very pretty on the outside which I assume is due to the previous owner using it essentially as a dirtbike around a campground. When I got the bike it had street tires but i was told when he got it there was a dirtbike tire on the back. Is there any companies out there that sell cylinders or were they ever reproduced? I've been searching all over but ones I'm seeing up for sale are on eBay and would probably be as much work to clean up as my own. My exhausts currently have part of the chrome gone due to I'm assuming acid spilling on them. I would like to do a 6 speed swap on them but haven't found much on doing so. I believe it was on this page I had seen someone saying you could put rd400 gears in it and I'd like to do that to mine but I'm not sure on how much would go into doing so. I have to split my case this winter so I am planning on probably changing the crankshaft out, hopefully gears and doing all new seals and see if I can fix the oil leak. I would like to bore it up but not sure what is the best size over to go to. I also was debating on putting rd350 cylinders on it but I would rather leave it piston ported. Any help or tips is greatly appreciated 
For a little background I am 18 and got this bike when I was 16 as it had sat in a barn since the late 80s. When I got it she was rough and I had done some work to it and got it running. My goal was to drive it my last day of senior year and while out test riding it and making sure everything was good to go a few days prior I was unaware that it was running lean and it burned a hole through the top of the piston on the left cylinder. Upon recently taking the bike apart since I'm planning on doing this build over winter I am led to believe it was rebuilt once before due to broken fins on the cylinders. The cylinders don't look very pretty on the outside which I assume is due to the previous owner using it essentially as a dirtbike around a campground. When I got the bike it had street tires but i was told when he got it there was a dirtbike tire on the back. Is there any companies out there that sell cylinders or were they ever reproduced? I've been searching all over but ones I'm seeing up for sale are on eBay and would probably be as much work to clean up as my own. My exhausts currently have part of the chrome gone due to I'm assuming acid spilling on them. I would like to do a 6 speed swap on them but haven't found much on doing so. I believe it was on this page I had seen someone saying you could put rd400 gears in it and I'd like to do that to mine but I'm not sure on how much would go into doing so. I have to split my case this winter so I am planning on probably changing the crankshaft out, hopefully gears and doing all new seals and see if I can fix the oil leak. I would like to bore it up but not sure what is the best size over to go to. I also was debating on putting rd350 cylinders on it but I would rather leave it piston ported. Any help or tips is greatly appreciated