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Yamaha Yz125 Questions

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Hi Guys

No rush to get this information, but at the moment I am 15, and am riding a 2002 xr200, maintaining myself and keeping in mint condition. I love it, and am getting better and better every time I ride. The trails, fun days you name it. Anyway, sometime next year I will be looking at taking the next step, and I have my eyes set on a yz125. A couple of friends have then and love them. Before I make this step, I have things I would like to know. I know the general maintenance like oil changes every 5 hours, air filter every ride, chain lube and tightness, top end done every 50 hrs etc.. But whilst looking at one of the manuals, it had extremes like changing piston every race, fork oil every race and the list goes on... This can't be true!! So yeah if you guys can clear this up for me if it is true or not please?? Also please tell me any general information that I may find useful about maintaining etc. Cheers :bonk:

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Yup... suspension fluids once a year minimum, top ends every 10-20 hrs depending on how fast you are. I change the tranny oil a little more frequently on my 125 than I do on my 250s because of how much the clutch gets abused. Gets changed every other ride.

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Ok so not to bad then. Yeah I keep getting told different things about rebuild time. I'm not going to race it straight away, so it would not be ridden to hard, thus meaning a rebuild every 30-40 hrs? This is also what I've been told. I apprciate you're guys help, and do you agree with me on this?

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Yea... I have quite a few buddies that ride solely on the trails and lug around with thier 125s and run thier pistons between 20 and 40 hrs. They all run forged pistons though because they are quite a bit stronger and arent as less brittle or prone to stress cracks and skirt fractures unlike cast which need to be changed at proper intervals to prevent these issues that could take out an entire motor.

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Read through a little of this and you will learn the benefits of each piston. Plus a LOT of biased opinions on both sides. Basically from what I understand a forged piston is stronger/ less prone to fracture but expand more rapidly, cast is lighter, typically produces better power and can be run at tighter tolerances. The main difference is the amount of silicon used in the process. The reason I run forged pistons is for the peace of mind that one is not going to drop a skirt in my cylinder and take the whole motor out with it.

http://www.thumpertalk.com/forum/showthread.php?t=947404&highlight=cast+vs+forged

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I would get it done professionally so would I just ask the me mechanic to order forged pistons instead?

Trust me when I say... Learn to do it yourself... its super easy on a 2 stroke and takes under an hour once you get the hang of it. If you knew how easy they were to replace and how much money you would save in labor... those words would have never came out of your mouth. You could buy 2 or 3 pistons for what the shop will charge you in labor to rebuild yours.

If you can read, and turn a wrench, you can rebuild your top end. Save your money for fuel, premix, oil, filters, gear and tires.

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I agree with everything ftball said.

It may sound intimidating to need to change a piston, but its actually so so easy that after you're done you'd wonder why you ever paid anyone to do it.

In regards to cast v forged, as ftball said the forged ones are less likely to fail, particularly when pushed beyond service limits (about 40 hours on a 125?). Supposedly there is a small power difference between them, particularly at less than 15 hours, however unless you're a pro rider you're unlikely to be able to tell the difference. Even then, there are so many other things to worry about which will noticeably improve performance (eg - jetting).

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Agree with fball 100%. Labor minimum is 75 an hour, so you just doubled the price of a piston and rings if you go to a dealer. Plus, youll have the benefit of knowing exactly whats in, on, and around your bike. Worst case scenario is you get stuck and take it to the dealer anyway. Might as well try it!

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Nah if you get stuck just come back on here and let us know what your having trouble with. We will help you out and get you going again. Keep your bike out of and away from the shop.

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Man that's awesome thanks. I don't have the bike yet butcher I do that will be really appreciate it. All the normal stuff is easy as but this will be the stinger until I get the hang of it, I mean how hard can it be? Out the new parts where the old ones came from lol. This kit would be good for the years specified http://www.trademe.co.nz/Browse/Listing.aspx?id=432620965

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