Hi everyone, I am confused by the process of adapting modern internals into a pre-65 type fork leg. I am an engineer by trade, but find it hard to visualise the process. Is anyone out there able to explain the concept?

Do you bore out the classic fork bottom? That would weaken it.

Do you make special bushes? That would be difficult, as modern fork stanchions tend to be of larger diameter than classic.

Do you machine the outside of the modern leg, and somehow fit the entire modern fork within the classic fork bottom?

I can only imagine that classic fork legs must be chosen carefully, with larger diameter ones preferable, or modern forks chosen that are close to the diameter of classic ones. Clues anyone?

Do you machine the outside of the modern leg, and somehow fit the entire modern fork within the classic fork bottom?

Yes, that's what is done - usually into Norton Roadholder legs, but original BSA or Triumph steel legs are used too.

Can't tell you how it's done, I'm not an engineer. I've heard it's a very fine tolerance between success and a balls-up when machining the parts though

Hi everyone, I am confused by the process of adapting modern internals into a pre-65 type fork leg. I am an engineer by trade, but find it hard to visualise the process. Is anyone out there able to explain the concept?

Do you bore out the classic fork bottom? That would weaken it.

Do you make special bushes? That would be difficult, as modern fork stanchions tend to be of larger diameter than classic.

Do you machine the outside of the modern leg, and somehow fit the entire modern fork within the classic fork bottom?

I can only imagine that classic fork legs must be chosen carefully, with larger diameter ones preferable, or modern forks chosen that are close to the diameter of classic ones. Clues anyone?

Try contacting Allen Whitton

Vinnie

i've not done it but have seen it done. the leg of the modern fork is reduced on the lathe to fit inside the original p65 outer. i'd strongly reccomend someone to do it for you the modern fork is taken to a very very thin state and it must be a nice tight fit in the old leg so too much and its scrap too little and the p65 legs cracks as the two are eased together

an engineering bottle test was how it was described to me.. and with roadholders very rare and thus expensive and mazzochis 150 a pair i wouldnt test my owm bottle.

what i found best was a set of very good conditioned bultaco forks. then brought a set of norton roadholder bottoms. turn down the bultaco legs on a lathe so they are a tight fit inside the norton sliders. you only leave a few mill on the bultaco sliders so be carefull.take your time. when you have done this i just glued the sliders together with aroldite or locktight adessive. then reasemble the forks and bolt straight through the bottom...job done. hope this helps.

Thanks for the replies chaps. I am simply going to have to have a bash myself now, just 'cos.

Thanks for the replies chaps. I am simply going to have to have a bash myself now, just 'cos.

Let us know how you get on, I have always wondered how it's done, and heard it is a very fine line between success and ba11s up as Woody said.

Good luck...

A certain well known trials engineer from Outlane nr Huddersfield turns down the modern units then threads them to screw into the threads at the top of the old forks.

No one has mentioned 'heavyweight' AMC alloy sliders. They have a clamp at the bottom meaning you don't have to have a knock out spindle. Easier to come by and just as good as Norton.

Good luck

Hi Guy's,

I am thinking of making up some glass-fiber covers for these so called modern forks ,with the profile of either Norton road-holders AMC,etc, made in two halves then clamped on with a couple of jubilee clips.

This is NO different than covering the modern forks with a alloy skin so it should be OK?

Regards Charlie.

Put some BSA stickers on a 4rt - same difference only a lot cheaper