Spacer plate: You can change the
power by removing the 5mm plate.
TAKEN TO ITS LOGICAL CONCLUSION Dear MXA, In the April 2013 test of the 2013 Yamaha YZ250 two-stroke, you said that if you remove the 5mm spacer from in front of the reed block you will get more top end. I want to know if this hurts the bottom end? Yes, it does. By removing the 5mm spacer, you are moving the carburetor closer to the intake port. This shortens the fuel stream and allows it to recharge the engine quicker, which pays dividends as the rpm increases. On the other hand, moving the carb closer also shortens the fuel stream, which means that you aren’t getting as much fuel at low rpm. Thus, you give up bottom end to get top end (or vice versa). ;