Yamaha YZ125 Legalise It!



  • Yamaha YZ125 Legalise It!

    Just porting over some of my threads over to this new site 😃

    First Update

    Yamaha YZ125 Road Legal

    So posting on behalf of my brother really, for those who are interested. He loves his YZ, even though he's only used it a handful of times. It's actually because of this he is going down the road legal route. From what he's said it shouldn't be too much work. He only rides a couple of times a year so reliability isn't really an issue. He just needs to contact Yamaha to confirm the year, Insure the bike. Get it MOT'd then get a plate. I think that's all he needs to do. But for the moment he's just making it road legal.

    He bought a conversion kit around £350 off eBay that is just lovely.

    Full loom, Headlight (with a horn inside the headlight) Handle bar switch, new stator plate, banjo bolts and tail tidy. Along with instructions and all the bits and bobs needed to assemble it. Bargain really. All came neatly packaged ready to bolt on. Most of it is done. He just needs tyres. But he wants to supermoto it so is just waiting for the right wheels to crop up.

    Anyway here are the photos.

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    I didn't get a photo of the stator plate. But I'll say this, It's exactly the same as standard bar one wire that has come off it for external power. That was all the eye could tell.

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    Second Update

    So we drove 250 miles to pick up some DTX excel rims for the YZ125.

    Big plans for the wheels on this bike. Personally I think my wheels (which fitted no mods) look wicked...

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    But my brother wants to use the Excel rims with the gold talon hubs.
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    Which brings me on to my next question.

    Does anyone know of a good quality wheel builder near Gloucestershire?

    Imagine those with the gold talon hubs, stainless spokes and gold nipples.

    Third Update

    Well three months later, the wheels have been built. £75 a wheel. Stainless steel spokes and a new Maxxis tyre just fits between the swing arm.

    Had a little go today and it is very good. Little problem with the sprockets as it does about 30 mph. Get's there like a bullet out a gun mind you. Very nice to ride. Proper supermoto.

    I have some spares that are not going to use. I will make a new thread with these items. Forgot to take photos.

    Any kinda wish I didn't go on it, makes my bike feel like a 400cc 50cc bike 😞 Heavy and slow. Ah well. It's nice to experience different things. I couldn't ride this bike everyday like the DT it's far too explosive. Very fun. My brother is over the moon.

    Just needs Insuring, MOT then registering. Not long now 😃
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    Fourth Update

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    Today!

    Oh dear... so the YZ gave up the ghost and we have no idea what has happened here!

    Plenty of coolant, plenty of oil but it's just seized and died. We reckon it could have been a few things.

    Either heat seizure, fueling, out of tolerance piston.

    I reckon where the bike is now getting ridiculous amounts of air, compared to a stiffled track, the engine is being super cooled. Contracting the walls of the cylinder against the ever expanding piston.

    However: I was surprised to see just how little coolant these machines use. And how small the water jacket is.

    So fueling is the next likely scenario.

    Where this is now being used to ride daily we're finding long runs with WOT may have caused the bike to run lean. Death Ash on top of the piston crown supports this theory.

    The piston of course just could have been well over due a service. However after closer inspection of this engine, it looks like it's been rebuilt with the use of a forged rod on it!

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    Notice lack of scoring on cooler intake side.
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    That's all folks!

    Do we get it replated, or new cylinder....either way it's going to be rebuilt.



  • Oh dear, looks like a combination of a piss poor fuel/oil mixture and piss poor carburation. Like you say a little to lean. Never seen that on any 2t MX or enduro bike and those little engines are built for hammer.



  • Lol. Yeag it is typical of my brother. He just couldn't ve bothered to sort the fueling out.



  • How did you get them wheels for 75 pound each buddy? Fair play looking really good 🙂



  • Ohh wow it would have been more than 75. The dt wheels alone cost a bit. Then they needed to be built and lots of other stuff.

    They were hand built and the excel rims laced onto the original talon hubs.

    Yeah the bikes nice but it wasn't what my.brother was expecting. Great bike to go to the shops on. Any further then its a bit shit lol.



  • Any progress with this ?



  • Engines being rebuilt the compression knocked back a little bit and the fueling increased then I think it will go up for sale. But not 100%