Missing rear axle spacer

[breakwellmz]

Hi.

Putting the back wheel back in my Mastiff i have a 4mm gap between the swinging arms but can`t see that i am missing any axle/hub components, i can`t be the only person to have done this!
What component am i missing?
I`ve done fingertip search of where i`ve been working but no no avail.
Cheers.

[Puffs]

If you're certain you didn't for get anything (see pic elsewhere), I'd just tighten the lot & be done with it.

It so happens I've been having fun in games with the rear wheel of my YZ yesterday, and I just checked for you: that has a similar sort of clearance.

No that's not the axle, just a piece of alu pipe.

[breakwellmz]

Thanks.
Have been out there again this morning and what appears to be missing is a spacer/washer with a thickness of 3.3mm, internal diameter of 20mm, and an outside dia. of 35mm.
Even if i could get rid of that gap by tightening up the axle nuts (Which i havn`t had to before, and i can`t anyway ) It would stress the swinging arm, it`s not like a bicycle with a flexible rear triangle.
I`m surprised your YZ swinging arm is that flexible, you sure you hav`nt a spacer missing?!
Cheers.

[Puffs]

Ah good that you found it!
A bit surprising actually, as in the drawing from section 27 of the Spare parts list

no such washer is indicated. Washers 31 sit below the nuts. Are you sure an extra washer is required? Anyway, if you feel more confident with it, go for it.

Yes I am quite sure mine is not missing anything. It's an MX bike, no such niceties as a separate hub for the sprocket, or any other such malarkey. Simple & made for quick & easy working on. And indeed, probably stiffer than the swingarm of such a Mastiff, considering what it is designed for. A bit of static preload can enhance stiffness and does not lead to fatigue, as it's static. See the drawing if you like:

On each side there is only 1 distance spacer, with a dust collar stuck onto it; unit 5 in the drwg. One side goes into the seal & onto the bearing, the other onto the swingarm. You can also see it in the earlier photo, and there is nothing else. And yes, that swingarm + it's solo shock linkage (with 32.5 cm wheel travel) has been tried & tested in mega jumps. Anything flexes under load (yes, even diamond), but I wouldn't say this swingarm is particularly feeble.

The arms of a swingarm are stiff in the up-down direction, not so much in the left-right direction, that is not required. A bit of clearance makes it easier to insert the wheel in a hurry, and some static flex & preload doesn't hurt. As it's static, it doesn't cause metal fatigue.

Note that the (hollow) axle goes in from the chain side.