Here I replaced my piston rings and lap my valves. How to remove your motor: • How To Remove a Motor/... How to rebuild your head: • How to Rebuild a Head ... How to clean your Carburetor: • How to clean, rebuild,...
Replacing the countershaft oil seal requires you to open the crankcases due to the outer lip reducing the risk of this oil seal coming out of the crankcase due to pressure into crankcase.
I get my gasket kits on EBay or Amazon. Other parts on Facebook group called: XL250s, XL500s, XR250, XR500 with 23’ inch front wheel only. This site has lots but it’s overseas. www.cmsnl.com/honda-xl250-usa_model50530/partslist/#.Y_iaqxZE2_Y
None on eBay at the moment but keep checking, one will turn up. Did you join the Facebook group (Honda XL250s, XL500s, XR250, XR500 with 23inch front wheel onky) yet?
Take the head off and add a bit of transmission oil on the piston and let it soak. Repeat this for a few days. Give it a tap with a soft face hammer. You will need to bore it out 0.010” over.