The timing map in the box was designed for a stock engine. The SRP and or Pro Comm boxes were also designed to specifically enhance the performance of a stock application. Once you make changes like increased compression or more efficient cylinder head air flow, you have to make adjustments to compensate for the increased performance.
As with any good build, be it ATV or Automotive , years of hands on experience, hundreds of thousands of dollars worth of R&D, tens of thousands of dollars worth of testing equipment, ( Dyno, Flow Bench, ect...) have taught us that not only using the best parts that the many different industries have to offer, the little things like tuning a quad properly, will not only yield the best possible performance, but will keep it running properly for many many hours.
A person can waist a lot of good money if they are unsure of what they want but really need, or if there builder does not have the proper equipment to do the job.
I hope all of my rambling will help you in one way or another. It is no secret that the YFZ's are probably the most prone to engine failure, but they can also be a good quad as well.
Mike
ATP Racing
yup ben through to many of them. was gunna get a suzuki but i already have tons of extra parts for my yfzs