time for rebuild

2 replies to this topic
  • yamahazinger

Posted February 06, 2005 - 05:25 PM


I know this is a 4 stroke site but you guys prob have had experience in doing this. I have a yz250 2 stroke and its getting time for a rebuild. This would be my first time rebuilding it myself, but my dad has had tons of experience and he knows what hes doing. Im just wondering what needs to be done. What things are necessities to be replaced. Any help with like what grit sandpaper i should wetsand a hone on the cylinder to what little item should be replaced. I know the basic things like piston, rings, circlips, wrist pin, needle bearing, ect. Does anything like dowel pins need to be replaced. I just need steps and list of parts and ill be good to go and if anyone wants i will be taking pictures throughout the process so just let me know if you want them. Ill let you guys no how it turned out. thanks alot dave

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  • Satch0922

Posted February 06, 2005 - 06:10 PM


it's not easy to answer all of your questions not knowing what shape your bike is in. You really should measure or have the cylinder measure to see if you need to rebore. If not a piston/ring kit may be all you need.

  • sirthumpalot

Posted February 06, 2005 - 08:44 PM


Do not hone the cylinder. If it's a nicasil (sp?) plated cylinder, or a cylinder with some other plating, then you can really screw it up by attempting to hone it. Plus cylinders with hard coatings don't always need to be honed or resleaved. First measure it, and if it's still in spec and has good cross hatch then leave it alone. If it's out of spec then decide on what to do based on your measurements (bore + replate, resleave, etc..).

If you don't have any special tools, then I recommend you pop the cylinder off and take it to someone who can measure it. You'll need to check things like is the head flat (warped), is the cylinder still round enough to be within spec (it will get elongated with hours on the bike), etc... Also get the feeler and check your rod free play and rod vertical movement. There are some other things to check too, but it's all in your manual. Just grab the owners manual and give it a good read and everything to check will be in there. In the least you'll need a piston kit, wrist pin kit and a gasget kit, some assembly lube and the right tools. Good luck and have fun!

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