Mikuni VM36 Re-tune Kit TT500 XT500 This kit consists of the suggested jets for changing that are not matching those factory fitted in the VM38-9, they include an extra one size up and one size down main jet for tuning the main circuit due to fuel quality variations, altitude and climate. Testing and conformation of correct main circuit jetting can only be done by physically changing jets and WOT testing. Generally these kits will offer a very close and useful starting point, however when considering anychanges to porting, compression or the numerous other things that contribute to the engines fuel needs, additional fine tuning may be necessary, but as a rule our kits are spot on. Keep in mind that these are suggested specs, and all the correct tuning procedures, must be adhered to for the confirmation of any supplied jets compatibility with your engine. Please Note:jets are non-returnable items due to the undetectable risk of tampering.