someone told me after 100 hours, you need to do a top end rebuild on the yfz. Is this true?

 

Don't worry about it...it will fail somewhere before rebuild time anyway.

 

LMAO!!!

 

I bought my YFZ 7-8-03 and have not had any trouble with the top end at all. I even have done the cam mod.[img]i/expressions/face-icon-small-smile.gif[/img]

 

something is up with mine... its started to loose power... checked the valves.... they were ok... so my next guess is rings...

 

it depends on how hard u ride ur machine

 

well whatever i buy i plan to drag race. but what i heard was that yamaha recomends a top end rebuild after 100 hours, i'm trying to find someone in the know to confirm or deny this

 

can someone explain to me why top end rebuilds have to be done and what and how its done?

 

Becouse the piston, rings, and cylinder wear out and you start losing compression. Depending on how weak your top end is, tells you what to do. I redo mine when the compression drops to low. When mine wears out I Bore the cylinder and replace the piston and rings. I am not familiar with 4-strokes but I am sure you need do something with the valves in the head also..


PS.. Modifiying you bike will make these parts move faster and wear out faster. [img]i/expressions/face-icon-small-sad.gif[/img]

 

Isnt the science behind it that the piston itself shrinks just a little bit and kind of wobbles around, therefore losing some compression as well? I see a lot of people go to .20 over on there rebuild, however, if its not knicked up in the cylinder walls cant you just still use the stock bore on it? Also, how exactly does a ring "wear" out, does it become more loose on the piston or ?