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YZ125 Engine Serial Number

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Just picked up yz125 as part of a barter. Frame is 05 according to VIN and aluminum. However, last 3 digits don't match the serial number on the case half. This leads me to believe that the cases were replaced at some point in its life...which is cool with me. But I just want to know what I'm dealing with in terms of year of engine. Is there anyway to tell what year cylinder and cases are on 05+ yz125, based on serial number on case and identifying marks of the jug? Ive scoured the internet and have come up empty... :confused:

 

Also, po "thinks its a 5 speed"...

Aren't 05+ all 6 speed...or is it possible the engine is prior to 05???

Edited by Cap N Jnz

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2004 was the last year of the 5 speed gearbox (2002 to 2004 from what I've read)

 

2005 was the change to an all new engine design and 6 speed gearbox

it's been the same engine design since then (2005-2016)

 

But, there are some minor differences from a 2005 versus newer ones.

The 2006 model got revised with a few changes to slightly improve power

(cylinder head squish, carburator adjustments, powervalve governor spring, CDI box)

 

Appart from the late model longer silencer and required jetting changes, it has remained unchanged up to 2016.

Edited by mlatour
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Good job on doing the serial number research. 👍

 

"Matching Numbers" on many models of Japanese motorcycles stopped quite a few years ago.

Outsourcing major components from a variety of suppliers & countries made it impossible to keep sequence matched between engine and frame.

 

If the first few numbers (1C32 ?) are the same on the engine and frame then both components are the same model year.

https://www.motorcyclespareparts.eu/yamaha-parts/model-prefix.aspx

 

Plus, motor swapping on late-model YZs is not that common because complete engines can be tough to find and can be very expensive (supply & demand). People thinking of "fixing" their "broken" motor by simply replacing it soon find it is MUCH cheaper to just repair what is wrong.

 

 

Yes, the 2005 YZ125 came with a 6-speed gearbox.

http://www.motorcyclistonline.com/2005/yamaha/yz/125/specifications/1364/05/

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Thanks guys. I read somewhere that the last few digits on frame serial and engine case numbers match as they indicate the production sequence for that particular year.

Engine serial is Ee18E-000358. So this engine came in the 358th produced yz of its particular year. The question is what year?

EE18E will identify the production year, but I cannot find a thing online. Apparently the 04 was something like EE16. Might be safe to assume it's 05. But my ocd rarely allows me to assume anything. Anyone out there with an 05+ yz125...id love to hear the first 4 of your engines serial number. Thanks again!

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Checking...

 

 

2005 YZ125. Engine # E118E-00XXX

Edited by CaptDan

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Excellent news Capt! No pic necessary. My ocd is satisfied. Shift stopper is on my list of to-do items (now that I know for certain its an 05). Im currently rebuilding suspension linkage and shock bearings. Before I post as another thread...do you know if the upper shock bearing sits against a lip or bevel on the resevioir side? Mine had no lip or bevel, and I was able to press the bearing out through the reservoir side. Is that normal...or is my upper shock excessively worn? There was also no circlip holding the bearing in place. However, there were 2 indentations around the circumference of where the bearing sits. I assume the circlip rests into this "groove" when mounted.

 

This is my first yz...so any help is appreciated!

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Good to hear. 👍

 

I have no clue about the shock's upper bearing, but I'm sure someone here will have an answer.

 

Good luck!

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