New piston



  • Hey guys I was just wondering how long does it take to wear in a mitaka piston and at what speed as I'm doing a top end on it next week and wondered how long I should wear it in thanks



  • Hi there, It's not so much about length of time or speed.

    It's about revs and miles really. Everyone has their own view and method for running in a new piston but heres a few points that I'd go by.

    1. Ensure you do a heat and cool cycle and then re torque the head bolts.
    2. Avoid revving the engine whilst its not in gear and being ridden ( dont sit there revving it to run the engine in).
    3. Use good quality 2 stroke oil and make sure the pump is set right and running properly.
    4. make sure your carb settings are correct and it's not over fueling or you'll be washing oil off the cylinder at an important time.

    The basic idea of running in a 2 stroke piston is that you want to avoid prolonged times of constant (the same) rpm. You want to vary it and gradually increase the revs allowing it to completely cool between leisurely rides.



  • Pretty sure it's not the piston you are running In either. Sure you want ti test metal fatigue, but the piston should pass a visual exam before use.

    You are more interested in bedding the rings into the bore. Avoiding glazing and the like.



  • I'm getting it done by a shop as I don't wanna mess the bike up myself so I'll get them to check the oil pump as I'm pretty sure it's getting to much oil cause it's burning through spark plugs. How many miles at low rpm would you guys recommend



  • Yeah as Cal says its the rings against the cylinder wall thats wearing but meh.

    Best bet is to call a yamaha dealer and ask them what they reccomend. probably something like 300-500 miles. But you want to vary it and use the gears. So dont run it round to red line. Set yourself to change gears at about 5krpm and avoid sitting at a single rpm. so if you need to use it for long journeys, wait til its run in.



  • I took it easy the first tankfull (no high revs), and gradualy opened it up on the next. Job done.



  • Can anybody tell me the thickness of the Cylinder head gasket? I don't have one to hand.