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I have just purchased a DRZ400s and I have an older DRZ400e on the S there is a pipe that comes out just above the exhaust it apears to be blocked off but is not on the E. Does anyone know what it isand or does and can it be blocked off at the cylinder head like the E it is a solid pipe going into rubber pipe. It blocks access to the fan and header. 

Also I have a Muzzy muffler on the E standard on the S I would like to swop them but notice between the Muzzy muffler and head there is no seal the header pipes seem the same. 

Thank you for any advice. 

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Ntmakia , it`s called the pair valve . It`s purpose was to bleed atmosphere into the exhaust stream to fool a gas analyser . You can buy a blocking plate off of e-bay for the hyabusa , it fits the DRZ . You could leave it as is if you want as it wont do anything . By the look of your pics the bike has seen some use , man that pipe is rusted . One thing to look out for is the mikuni carb has a solenoide attatched to the bottom of it and it lowers the air pressure in the diaphram so you cannot get full throttle in the lower gears . Have you ever heard of the 3x3 mod ? It is the size of the air intake to the airbox your E should have it so compare it to the S , Just check out the intake hole in the top of the airbox , it will run better if you do it and rejet the carb if you change the pipe . About the exhaust , if I get you right , you mean you dont have a gasket ? They normally are there , hiding in the exhaust port . When they get carbon on them , you cannot see them and it looks like the exhaust just sits into the port . If you are going to retire the E , I would think about changing over the keihin carb and the cams as the S is detuned and does not have the same carb , cams , pipe , compression and airbox , greg

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Exhaust air injection is very common and does more than just "fool" the gas analyzer.  The added oxygen supports burning in the exhaust and is particularly effective in conjunction with catalitic converters.  Many cars have used exhaust air injection since the mid 70's.  As long as it works properly, it has no affect on performance.

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