welcome to the forum. In regards to your question, it is unfortunate but these machines are nothing but small details. They are extremely fun and rewarding. However, they do require much maintenance and this is where a lot of us get our reward but also some of our frustrations. Also, no two engines are alike due to the quality of the motors. You may have to change out some parts on your kit. No one really knows what they will need until they attach the motor to the bike. When ou do have a qustions, try evryone hear. At least one of us may be of help. You may want to start reading through some of the posts here:
2 Stroke Bicycle Engines & Kits - Bicycle Motor at Motorized Bicycle Forum
As for the Sick Bike Parts, I do not have one installed on my build. However, I have read great reviews about them and the guys are very helpful with any concerns or questions.
Overall, the best plan for building a motorized bike is to be flexible.
Welcome to the fun, good luck, and be safe.