Yamaha YZ 125

[Anabolic]

1999 YZ 125

Welcome to my YZ 125 thread

I got this bike around 6 years ago and she was in a state. I near enough fully restored her around 5 years back.

She has been sat now for 2 years after the power valve rod arm snapped.

Anyone know what would cause this? Just wear and tear?

Ive started this thread for some motivation as i want to get her running again.

Heres a picture of her after the rebuild a while back.

https://img580.imageshack.us/img580/1415/yz125.jpg

WATCH THIS SPACE!

[N cee thirty]

was just wondering,whats the difference between that bike and a dt ?

cheers
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'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[woll]

Yz is a more highly tuned engine than the dt. And there are a few other bits that are better than dt spec parts iirc.
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Current Bike- Suzuki DRZ400 SM K6
Previous bikes - Derbi Senda Xtreme50r, Honda CBR 125, Kawasaki ZZR 250, Yamaha DT125R, Suzuki Bandit 600, Gas gas ec 250, Honda CBR600FW
Damaged spleen, damaged kindey, 2 popped lungs, 2 broken ribs, broken face, broken wrist and 5 back fractures... remember kids walls hurt

[Anabolic]

DT = Onroad bike

YZ = Offroad bike

YZ are quicker than the DT

DTs are nice onroad crossers but for offroad you cant beat the YZ

I love them

[delvey91]

Looks alright

Dunno how the powervalve works on those but if its a spring operated one i have heard of the springs snapping and causing a rite mess

[ms51ves3]

[Anabolic]

THESE PARTS ARE NOT FROM MY BIKE, THIS IS JUST TO GIVE YOU AN IDEA WHAT THE PROBLEM IS

The rod you see at the top of this picture is whats snapped

I got a new one and this cost me around £85

https://img186.imageshack.us/img186/216/rodarm.jpg

This rod follows to the exhaust valve governor

https://img828.imageshack.us/img828/6627/exhaustvalvegov.jpg

This could be shot to (hope not)

I will pull the crankcase off when i can and have a look

[ms51ves3]

Nothing like a YPVS

[stevo as b4]

The YZ YPVS is much more complicated and is mechanically operated like nearly all MX bikes are, and some trailie's like the Kawasaki KMX and Honda MTX etc.

It has a combination of a guillotine blade exhaust valve to work inside the main exhaust port, and 2 smaller cylindrical shaped plungers that open and close the exhaust sub/boost ports, and may also open the passage way up to a resonater chamber.

The DT, TZR, and RD350/500's spool type YPVS valve is wonderfully elegant and simple in comparison, and being electrically driven means that all those linkages, springs and govenors are not required. The downside is that the spool type YPVS can only raise or lower the main exhaust port, and cannot change the volume of the exhaust system or open additional boost ports etc.

The YZ and most other MX engines have a combination of the original YPVS and the original KIPS designs to combine the best features of both systems.