Home Forums Shifter Karts CR80/85 Tech Talk Reply To: CR80/85 Tech Talk


William Martin

Top end rebuild is straightforward…not necessarily “easy”, as it takes some care to get it right. You will want a flat plate with a slot in it to slide under the piston so you can pull it down to the plate, helping you not twist the connecting rod while you extract the wrist pin. You really need a pin puller, but it can be removed by heating the top of the piston with a propane torch until the pin can be pushed out with “very little” side force on the piston. Never force it…that’s how rods get bent. When you have the old piston removed, use it to push your new ring into the bore about a half inch down the bore. Measure the end gap of the ring (feeler gauge), make sure it is within the specs that should be on the paper that comes with your replacement piston/ring/pin kit. If it’s too tight you might have a ring “stick” when it gets hot. If you don’t have a tool to insert the new clips in the piston pin bore grooves, be really careful not to nick up the piston or shoot the clips off into space…it is tricky. Pay attention to the markings on the piston top so as to get the new one in pointing in the right direction. Put some of that gooey pre-lube oil on the wrist pin bearing prior to reassembly, as well as on the piston skirt. Keep everything very clean, including your fingers while you do this work! Put a non-fuzzy towel over the open top of the engine crankcase, no extra stuff wants to be falling in there. That’s all that comes to mind…if you already knew all this, apologies for boring you…if I left out anything important, someone should feel free to chime in here and add information.

Good Luck,