Yamaha Dirt Bikes Forum

hey i have a 2002 yz 125 bought begining of this year. and it still runs great, im just wondering how often these bikes need to be rubuilt?  
1996 kx 80
2002 yz 125

Roughly every 30 hours.  
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No pain; No gain

Or when it gets hard to start, or you compression gets low.  
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No pain; No gain

What type riding do you do?  Any idea how many hours on the existing top end?  Are you the original owner?

The hours you can safely get depend on a number of things.  How hard the bike is ridden, pre-mix ratio, keeping a clean air filter on it etc.  
Dave H 2006 YZ250
(2008 YZ 125 son)

You should pull it apart and check everything for spec every 45 hours: piston, ring end gap, cylinder diameter. I do mine once a year, even though I get a lot more hours then that. It makes it easier because I can just do it in the winter.  

45 hours? I was told 30-35.
But I suppose it depends on type of riding.  
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No pain; No gain

nope. 45 hours, your actually suppose to change the rings every 15 hours.  

Really? Wow.  
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No pain; No gain

i that honda says every three races or every 8 hours for the piston on my old cr..

i thought that was a bit ridiculous even under racing circumstances but hey, they are making alot of money off the moron that actually reads this and buys a piston once a month lol  

The newer manuals are more accurate. Mine says exactly what I said and so do manuals for most bikes now.  

ic ic cool, yeah that cr was a 2001, and awesome bike, i just couldnt justify doing it that often.

but yeah even with racing here and there and riding as hard as i could i still just did a rebuild every winter when i got that extra time and cash for christmas  

Bill pulls his top end apart every 45 hours and everything comes out still in spec, and still replaces it. The advantage of that is that you will never have to get the cylinder replated. I personally think a top end could go at least 60 hours, if I get a few extra dollars around I might find out exactly how many hours I can go on a top end. I have probably 50-70 on mine now and it feels like its losing power. Its not really noticeable and I doubt most people could feel it, but I am really touchy with my bike because I ride it a lot harder.  

yeah i hear ya there.

i think you could honestly get 100 hours on it as long as you were good with your premix, you said you were using bel-ray h1r or honda hp2 right??

honestly i think its possible if everything is totally in spec and the tolerences are good when you put it together.

that would be really interesting to see if you went through with it  

All engines depend mainly on 1 thing!  and that one thing will determine how it acts the rest of it's life....Break in period.  If you break an engine in properly it will last forever,  if you don't  it won't Honda is full of it, and just like Edisons light bulbs are still burning, when was the last time you bought a light bulb that lasted 100 years?  That's right the companies are only interested in selling more parts,  they lie,  just like your government lies,  911 was an inside job and ring jobs depend on how you ride your bike, mainly on revs.  I get well over 150 hours on a set of rings and that is because I don't rev the hell out of my engine, just because they make them to rev to 13000 that don't mean it is good for the engine,  I don't rev mine above about 9000 but mostly not above 5500.  I use an iridium br7eix and it has hundreds and hundreds or should I say about 10,000 miles on it and looks exactly like it did the day I put it in and acts the same.  If you putt around the way I do with any other type of plug it will foul and you will think that the bike has to be revved to run, not true!  Find the right plug for low revs,  then be nice to your engine,  if it doesn't have enough power putting around, then it is too small!

 I had a ford ranger that I put 600,000 miles on and it had perfect compression and NO RIDGE at all!  That is because it was broken it properly by a handicapped person with hand controls!  All my motorcycles are the same way and I had 21 bikes before I turned 18 and put at least 50,000 on each one,  I have never hurt an engine until the other day and that was my fault, but it you don't rev them up to the max they will thank you for it and you'll find that those numbers on rings and rebuilds are only for people who ride bikes with engines too small!  Don't be scared of 500's ....you don't have to twist the throttle, but if you need it it's there!  

With the comments about goverment and 911 you might wanna watch. 911 is a big part of why im where Im at, doing what im doing. And this is one oh boy that aint scared of 500s. Im calling bullchit on the 600,000 miles on a ford ranger. Not a chance in hell did that motor have perfect compression. A motor wears because of friction heat, and other factors. a piston doesnt go up and down a bore for 600,000 miles and not wear a ridge and lose compression. Sorry dude doesnt happen, I dont care who the damn thing was broken in by.  
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