CAM2 , Sir
Your responses seem to be the most honest and educated. Thanks. I am new to the YSR scene and I appreciate your continued input. I have a few more bits of info and questions. Maybe we could do a phone conversation sometime soon, as it would probably help me much faster than this messaging method. Just so you know, I live in Florida, USA. I bought the bike on EBay and the seller was in Tennessee. So, once I won the auction I was committed. Anyway....
Here are the bits of info and questions:
1. The original owner was an avid motorcycle and YSR/NSR owner. He had about 4 other YSRís and a few Japan imported NSR 50/80ís. He also had a total of about 25 other motorcycles/atvís in his garage. He was rather wealthy and he told me he loved working, riding, and collecting bikes. I was impressed with his shop and his collection. He was also a pilot (owned his own plane). I was actually amazed at his love for bikes and tinkering.
2. I asked him about why did he go with the GT80 conversion and he explained to me that YSR 80 engine parts are very hard to come by so thatís why he did the GT80 conversion. He said its a popular option because of easy engine mounting and plug-and-play electrical connections.
3. I asked him why is the GT80 was only rated at 5hp and the YSR50 was 7hp stock. He explained that the YSR had better ports and an expansion chamber exhaust. He explained that a GT80 motor with a good pipe on it and proper tuning could easily match a YSR80. It made sense to me.
4. I have tinkered with 2 and 4 stroke bikes and jet skis , I know what proper jetting and good compression can do for a motor. I had a Yamaha 650 Superjet jet ski that blew me away after I did a port-match job on it, milled the head, and increased the jet sizes. It was insane.
It hit the rev limiter the instant you hit the throttle!!
So...Now, a few questions:
1. What is a safe compression number for me to aim for with this motor. Iím getting 120psi on a cold engine right now. Previous owner said it was a fresh top-end. Team Calamari said thatís a good number. I want this bike to be street rideable on pump gas. 91-93 octane is what we have here in Florida USA.
2. Is milling the head to bump the compression up a bad idea?
3. The bike has a Mikuni Round-Slide 20mm carb on it now, the previous owner gave me a nearly new Mikuni Flat Slide 24mm, do you think I should consider installing/tuning with the 24mm or just stick with the 20mm for better overall street-use considering Iím planning on using pump gas (91 octane). I have easy access to 100 octane aviation fuel, but I want ease of use and reliability.
Thanks, hope to hear back soon.