Piston Rings Replacement

[flyinacez]

Hey guys, I pulled the top end of my bike yesterday to replace a shift fork in the bottom end. Nothing wrong with the top end but in the manual it says to replace the piston rings regardless whenever the top end is torn down! Is it totally necessary, or will they be ok??
Thanks

 

[skylarc180484]

if they arent too worn they should be alright. we gota spare engine for our 3 wheeler from a salvage yard because i put the chain through the engine case. it smoked a bit so we ordered rings but the wrong ones came in and my dad wanted to get it together so we got all the rings that werent wore as much from both engines and put it together. it works fine, it doesnt smoke and has lots of power. on every other machine ive had we have just used the same rings as well

 

[DeathShadow]

Not replace the rings but id re-hone the cylinder.

 

[boxhead]

Agree with that one, re hone it so the rings will seat properly again.

 

[flyinacez]

Well the reason why I started this thread was because I put the topend back on and did not replace the rings or hone and she wont start. Compression tests suggest that it may be the rings. Not much compression as I turn it over, but when I put some oil in through the spark plug hole and crank it the compression builds up almost to specs. I bought a gasket kit off of ebay that had the whole topend but the bottom gasket was not like the original, kinda just like paper. Does that matter. Anywho gonna rip it apart and rehone and get some rings too. Hopefully that should solve the compression. I checked the valves and put them to specs but no improvemnt. The crank had seized so I replaced it and didnt change anything so I figured it should of started once I replaced it and put it back together?? Thanks for the info