Yamaha yz125 ?

[chopper]

 
  Ive just purchased an older motorcross bike and am not quiet sure what it is. the frame number is 2k6-000221 and the engine number is 2x3-000403. It is air cooled, has a rear mono shock, plastic petrol tank, and came with a yamaha mx125 parts manual printed in 1973. When reading the parts manual i noticed it showed 2 rear shocks and this bike has a single rear shock. Any help identifying the year make and model would help ? Thanks. 

[motomaniac]

its a 78 yz125 frame with a 79 engine or bottom end.

[dave]

How do you buy a vintage motocrosser without knowing roughly what it is?

[chopper]

 Thanks for the help motormaniac.
 Dave, when i brought the bike i was told it was a mx125 and it came with that parts manual. i thought it may have been a late 70s, yz125. I just needed to know for sure  so i could start buying the right parts to start restoring it.
This is the first vinagte motorcrosser ive owned. So only a beginner !

[mainline]

there's a few guys on here with either 78 or 79 model Yz125's so you should have no problems getting any help you need to fix it up.

[mainline]

except me of course, I don't know what I'm talking about

[Nathan S]

Funnily enough, I bought a similar bike a few years back - 125F motor in a 125E frame. As a race bike, the other way 'round would work better, but meh...
The YZ125Es are a sweet handling bike with no impossible to buy parts and no real trouble spots - they're hugely under-rated, simply because they're too new for pre-78 racing and are outclassed by most of the other Evo-class race bikes.

Airboxes are hard to find (dunno why people are so keen to rip them off), I've seen one cracked frame (around the top shock mount/down-tube area), and the footpegs can come loose (occasionally wrecking the splines on the frame, but usually falling off first - and only if you completely ignore the many warning signs), but that's about the limit of the likely problem areas.
If you just want a bike to ride around, many bits are the same as monoshock DT125/175 so they are a common source of cheap parts.

Between Viper666, Mainline, DG26, myself and a few others, there's not much that we can't help you out with.

These links will help:
http://yz125f.blogspot.com/
http://yamahayz125e.blogspot.com/

Scott does top quality, very authentic restos - so if he says it is so, then it is so! He also makes very good reproduction mudguards and front number plates.

except me of course, I don't know what I'm talking about

Sigged!

[dave]

Thanks for the help motormaniac.
 Dave, when i brought the bike i was told it was a mx125 and it came with that parts manual. i thought it may have been a late 70s, yz125. I just needed to know for sure  so i could start buying the right parts to start restoring it.
This is the first vinagte motorcrosser ive owned. So only a beginner !

Sorry Chopper I didn't mean it to sound negative, I just thought it sounded risky (I've been burnt too many times now to know better) and I've shyed away from the unknown. Too many shonky sellers out there.

[oldyzman]

Hey chopper, I'm with Nathan on the 125E-top model, that was my first VMXer, i will never sell it- so light to ride.
OLDYZMAN

[Viper666]

Chopper, I put a 78 engine in a 79 frame for my daughter as she couldn't use the more peaky 79 motor but the 78 has better pull from down low (Porting).
As nathan said the are plenty of parts around & even the odd complete engine. Be careful though the 77 & 78 YZ models all had "Cups" in the crankcase for the main bearings which work loose. They can be fixed by welding before they come loose or replacing with steel caps. If you want the best of both worlds put a 78 barrell on the 79 bottem end. You will need a 78 chamber (They fit inside a bolt on flange where as the 79 fits over an extruded port from the barrell) or in a pinch put the 79 over the flange but seal from the inside with salastic.

Viper666