Just reassembling a 1972 Montesa Cota 247 and cannot get the folk tubes though the yoke holes. Can anyone advise best way without having to open yoke expansion split with a chisel? 

You need quite an aggressive twisting motion of the fork leg using a clockwise and anticlockwise motion as you push upwards to get the fork leg started in the yoke. Some WD40 on the surface of the leg might help. If you've got the pinch bolts fully slackened you should not need to prise the yoke open any further.

Edited November 22, 20178 yr by cleanorbust

I use a thin wedged screwdriver bit, tapped into the gap between the pinch bolts to open the yokes.

 

A little grease on the yokes never hurts,

It's fairly common to need to open the fork tube clamps a bit.

If you've had the tubes re-chromed sometimes they end up slightly bigger in OD than original, but even standard tubes sometimes need it too.

If it is only the second (upper) clamp that is causing problems, it might pay to check if either of the clamps is not quite straight.

Another option is to fit the tubes through the bottom clamps without the top clamp, then fit the top clamp, rather than try and slide them through both clamps at the same time.

I use an old tyre lever that has a thin edge.  I remove all bolts from the clamps and wedge the tyre lever in just to open the gap slightly.

Adding WD40 to the legs as they come through the yokes helps but can make it harder to pull them through.

any lubricant will aid insertion.

But also twisting when installed.

Wedge open, plastic wedge is best.

I've had the same problem, i found heating the top yolk with a hair dryer suprisingly did the trick!

 

Thanks everyone for your replies. I have ended up using a cross section of the advise provided ie WD 40, twisting motion etc, but what really did the trick was light use of a heat gun on top and bottom yolk - so problem solved and on to the next challenge which I'm sure will be lurking just round the corner!!