Need help identifying this Yamaha Monoshock!

[IT400C]

Hi Guys,

I'm trying to identify a Yamaha Monoshock I have.  It's not a 1976 monoshock, it has the 1975 membrane housing, but the end of the shaft isn't correct either (from my limited knowledge of MX/YZ B's).

Any help would be greatly appreciated.


'76 on the bottom - unidentified on top of foto


looks like a '75 membrane housing (again, '76 on bottom for comparison)


'76 on left for comparison


This is where it gets odd - longer shaft and much larger diameter thread - same as shaft, no step down.


Anyone know what it is?

[IT400C]

I've never seen a YZ125X/C monoshock, is it possibly one of them??

[steveo247]

if no one can tell you, ill take some pics of my X monoshock tomorow to compare.

[IT400C]

Thanks.  I'm actually a little surprised that no-one's known it so far....

I got it cheap a couple of years ago, was after a spring, and the guy sold me the whole monoshock.  I just assumed it must have been an MX400 shockie, but it seems it's not..

Just confused by it!!!   

[Nathan S]

YZ125X/C shock is like the other one you've posted the pic of.

Part numbers of the usual suspects (YZ-Cs, MX-Bs, YZ-Bs and YZ-X) all show the same basic shock.
I then started looking at road bikes, but they all seemed to run twin shocks until well after Yamaha had dropped the membrane type seperator.

My best guess is that it might be a 74/75 build shock, with some sort of aftermarket extra-travel kit in it???

[IT400C]

Well, at least I know what it isn't now!!   

Bloody thing!

[motomaniac]

Could it be a YZ360B shock . Or maybe someones modded it.

[Hoony]

Anyone know what it is?

they aren't shocks, I reckon its Jeparties legs from the magic roundabout

[Nathan S]

YZ360B shock shaft has the same part number as all of the other likely options (YZ-C, etc).

[motomaniac]

There were long travel kits offered for these by companies such a s White Brothers. I only ever saw them advertised but by what I can remember the kits added a bolt on extension to the shaft and moved the bottom out bumper along to allow more travel.The result was 8& 1/2 to 9 inchs travel.

[IT400C]

My best guess is that it might be a 74/75 build shock, with some sort of aftermarket extra-travel kit in it???

There were long travel kits offered for these by companies such a s White Brothers. I only ever saw them advertised but by what I can remember the kits added a bolt on extension to the shaft and moved the bottom out bumper along to allow more travel.The result was 8& 1/2 to 9 inchs travel.

I think you could both be correct.  I just had a closer look at where the threaded section joins the main shaft, and it does look like it may be screwed on over the top of the original end section... 

My only problem is that the threads are stuffed where the end would have gone through the frame member (near the steering head)...      So I can't get the big nut off the end and remove the springs...   :'( :'(

[IT400C]

I'll try to take some close up photos of that area and post them later..

So - next question...  Would that shock be legal on a YZ250 or 360B?  Not that I own one, just curious.  It would appear to be a period modification.  Or would the actual kit type need to be identified to see if it would have been available to YZ-B owners pre-75?   

[IT400C]

If anyone else has any ideas, still happy to hear them!  We're only at the 'possible answer' stage at the moment...

[motomaniac]

If you can see a join -that was my next question - then its definitely a white brothers type longtravel kit.

[IT400C]

If you can see a join -that was my next question - then its definitely a white brothers type longtravel kit.

I think I can see the join.  Where the base of the threaded section joins the chromed shaft, the thread run-out appears WAY too fine..  I'll have to get some contact cleaner out later and clean it up a bit though.