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TWISTING FORKS, IS THIS ANORMAL THING ON THE 400/4?

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Laverdaroo:
Morning all,

I've not done one of these 400/4's before and undertaking a full build up and a bit of a swap of this and that when I pop it back together, I have a question regarding the  forks as I've not worked on these sorts of brakes before.
With all the front end assembly all built up after cleaning, stripping, drilling, (just finished the disc, easier than I thought!) and ultimately swearing, I notice that the fork leg with the calliper holder on actually rotates about 15 degrees when you twist it slightly. I presume this is the slack being taken up by the adjustable screw that dictates the setting of the fixed pad against the disc?

Is this right or have I missed something out of the build?
There's no front mudguard on the forks and I don't think I'm going to fit one but will this mean I will need some sort of fork brace to stop this twist or can this be dialled out via the adjuster screw once all together?

I'm no way 'green' at this sort of thing after building bikes for years on and off but just simply not too sure, can anybody reassure, help, suggest a fix or simply take the piss for being sausage fingers and forgetting something?

SumpMagnet:
Forks flexing was normal back in the day to a degree.

Front mudguards were effectively a brace, being of decent gauge steel, and in the 80's when everyone started fitting fibreglass aftermarket mudguards when the originals rotted out, fork braces became common.

But..there is nothing to stop the fork lower rotating 360' other than the wheel/spindle etc. so if your rotation is with a disc in the caliper and pads etc. then there shouldn't be massive amounts of space there. Does the brake work? Or have you not got to that stage yet? Is the front wheel in, spindle done up etc.

Laverdaroo:
Nothing is rigged up yet, Im just on with the dry build after getting the frame fettled and making sure all my little bags are empty from disassembly. Im meticulous on strip down but fully aware these little 'fingies' get lost or put to one side to replace and don't ever make it back in the bags. I just wasn't sure if there was meant to be this sort of twist. Its not much but what with this sort of brake set up I didn't know if it was normal.

Pretty sure she's back together in the right order as I've trawled the specs and the fiche's but there's always room for error in-between that last cup of tea and this one.
In my defence, I did get side-tracked building the rear wheel last night, which took me ages! Hadn't done a spoked rim before, bit of a head twister!

Its probably prudent to get the lines ordered and fitted and have a test but you know when it just doesn't look like it should be like that, it sets your mind off on a question fest! ::)

SumpMagnet:
I only ever had one bike ( A Moto Guzzi ) that had fork lowers keyed onto the stantion. Every set of Japanese forks I have taken apart has just had a damper bolt up the centre, and the fork lowers were free to rotate. As you clamp up the wheel spindle and spacers, the mudguard and the yoke pinchbolts, it should all settle into place.

But yeah....if when everything is bolted up properly things still don't feel right....then it really is time for concern.

But it looks like a nice little project you got going there. I personally am not a fan of drilled discs....but when I saw the bike in the background, I can see why you did it. Does fit with the style of machine you are putting together.  My 750 build is stalled on a front end issue...but that's aftermarket head bearings that simple do not fit!

K2-K6:
Presumably brake arm and it's pivot are free to move,  that's what makes the caliper action independent of the fork rotation. Spindle needs to be clamped fully with the clamps fitted in correct alignment too. They are usually arrowed for direction.

Fork bracing is a myth in my view,  the "brace" on a mudguard doesn't remotely have a load line that can help.  It's just to competently hold the mudguard and prevent that from getting near the tire.

They where obsessive about bracing in that period, and completely illogical in making aftermarket rubbish to sell.

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