33 replies to this topic

[oranagamcs]

I recently purchased a cub to convert into trials trim. I am trying to decide what is the best route to go with for the front end. The bike I have has the heavyweight front end on it. I have read about putting modern internals into the heavyweight forks. I think this may be the way I would like to go with the bike so it looks period correct anyhow. Does anybody have any idea of which parts I neeed to source to make this conversion or a idea how to do it. I have a very good machinist down the street so maching down the legs should not be a problem. Maybe there is someone in the USA doing this conversion?

Cheers
matt

[totalshell]

just had this done brilliantly in the UK
you''l need the appropriate legs to put in your cub sliders ty175 i think are the stuff or if you fancy going down the expensive route ( you know you want to) a brand new set of mazzochis legs
once youve got the lehs make sure you have the yolks to fit your new stantions .
basically the new legs are turned down so that the new sliders squeeze into the cub sliders you can go really thin as the cub sliders support the metal then fit to the yolks and away you go
couple of people doing very them proffesionally in Lancashire/ yorkshire dont have any idea if you can get it done in the wild west
althogh if you want to work to a budget and just get out and ride a simple refurb of your heavyweight forks will be more than adeqauet and a lot lot cheaper
best wishes

[Old trials fanatic]

Totalshell is right :agree: however a lot depends on the rules and regs applicable to the Trials you ride in.

A cheaper alternative is to use Betor forks either Bultaco, Ossa or Montesa. get them turned down so that they fit into your existing bottoms, dont forget to line up or re drill the drain holes though.

Re the yokes most over here use Billet alloy ones but a cheaper alternative is to use Montesa or Ossa ones. The Montesa are particularly good as on some years the clamp bolts are inboard of the fork legs and this satisfys some Clubs over here.

One thing to be aware of when trying to use yokes other than the billet alloy ones is will the fork legs be parallel to the yoke spindle and headstock? otherwise the front end goemetry and wheelbase will be affected.

Good luck and a very worthwhile mod. Youll be wanting a 230cc conversion and the crankcases modifying next ?

Edited by Old trials fanatic, 31 December 2006 - 10:24 PM.

[oranagamcs]

This is a total ground up rebuild on this bike. I picked up a complete cub vin T20SH2026 its titled as a 66. The motor is supposed to have a fresh top end, but i will have to split it to change the sprocket , so a big bore may not be out of the question. Do they really need them? Haha more power is always good right? Not sure if I really want to go into the motor now as I just finished a turboed Hayabusa for the dragstrip. My main concern is getting the suspension and chassis set up correctly on this cub first then go through the motor second. Are the Sammy Miller swingarms the way to go in the rear or is their someone else making arms for them? Can I modify a stock arm? Sorry for all the ?'s i am a newbie, but want to build it right the first time, even if I cant ride it to its potential. As far as rules and regulations, the local club in my area is pretty relaxed about rules, but I want it to look the part.

With the modern internals in the old forks what hold the lower legs into the triumph legs? I suppose you just machine the top of the new lower to fit the old cones/cups that hold the boot on also. I would not be against sending my forks over to get them done there, depending on the cost. Who would I contact? Again thanks for the help everyone.

Happy New Years
matt

[totalshell]

the forks should be such a good fit that once you put them in they will never come apart. ihad seal carriers made for mine

the swing arm is essential for a 4 inch tyre if your ever going to come across any mud at all, you can widen your own but if you want to buy miller and alan witton can both sort you out, alans work is bespoke and you will have to wait i have just seen a James frame he has just built and in the raw steel it was a work of art the miller stuff is off the shelf and ussually shiped same day

all of millers stuff is fit and forget it fits with little or no work and does what it says on the tin one of the best pieces of kit he has are the foot rest hangers they bolt straght on and put you right where you want to be on the bike

getting your forks 'done' in the uk is not cheap my complte front end minus wheel with new mazzochis, billet yolks taper bearings and no expense spared came out at close to 1600 US.. they are beautiful though and sooo smooth compared to even the betors that i used to run

[Old trials fanatic]

Frame wise if you want the best get a Macdonald cub frame.

totalshells right about the James frame that Alan does i've got one.

Piccy below but remember it's only work in progress so theres still a lot of work to be done so dont take the p***

The forks that are fitted, if you can see from the photo, are Marzocchi inside Norton outers as described above along with billet alloy yokes also as the above post.

You pays your money and takes your choice.

http://i4.photobucket.com/albums/y117/NVT1...ames271206b.jpg

Edited by Old trials fanatic, 01 January 2007 - 06:52 PM.

[totalshell]

yep thats the witton frame really looks the business, your forks are almost identical to mine except i had my yolks in black ( trying for that just built in 65 look and it works)
alans riding a very nice cub himself at the moment

[oranagamcs]

OTF your bike is really nice looking more pics, I know its not a cub but its great. Totalshell is there any chance you can post some pics of your bike and its front end. After some thought and searching I found a guy on ebay that has a set of sliders and 35mm tubes he says will make 31 inch forks with 6.5inches of travel. Is that what I am looking for? I can get my machinist to make the triple clamps. I just need a few pics of the conversion and clamps I am pretty sure I can get it together with a bit of thought and time at the machine shop. The part I just don't undertand is which slider you use for the axle attachment. Do you mill the bottom of the new turned down slider so you still use the triumph axle attachment? Then what holds the new slider into the original, cant be just locktite. Or do you simply use the whole new slider turned down with the old triumph slider acting as a cover, with the bottom milled off.. Pics would answer alot of questions. I have searched a few websites over here and cant really find anyone doing nice pre 65 bikes. Just looking at pics of your bikes is a wealth of information. At this point I want to do the modern internals myself or just refurb my stockers and then as my riding gets better switch to the modern internals.

Cheers
Matt

[Old trials fanatic]

Sorry havent got any pics but will try to explain.

1. Mill the spindle mounting off the new alloy sliders. Then machine turn the new alloy sliders into a slug. By that i mean like a tube with a smooth outer. You can and have to go very very thin on the wall thickness here so measure the internal dia as well as the outer dia. the idea is that they will be an interference fit into the existing sliders once they are machined.

2. Machine the existing sliders to a smooth bore interference fit on the now machined new sliders. You will be using the existing spindle mountings etc of the existing sliders so all the machining is internal. Dont forget the hole at the bottom to take the damper rod securing bolt.

3. Warm up the existing sliders and cool the new sliders. Apply loctite and insert the new sliders into the old outers. MAKE SURE YOU GET IT RIGHT HERE AS YOU ONLY GET ONE SHOT AT IT.

4. If you havent made sure the drain holes lined up before you assembled the sliders, best option, then you will need to redrill new drain holes at this point.

5. Now flush out the sliders to get rid of any remaining swarf, VERY IMPORTANT, as if you dont the stantions will be damaged as will the sliders.

6. Refit seals and off you go.

You might have to get seal retainers made up but most just have an alloy outer turned to take fork gaiters to retain the original look.

The reason a lot of people go for Norton sliders is they have a bit more "meat" on them than the Triumph ones. On the other hand the Triumph ones are steel and do retain the original appearance.

It is fairly straight forward but also very easy to trash a perfectly good pair of forks. Thats all down to how good your machinist is.

Good luck

Edited by Old trials fanatic, 02 January 2007 - 07:15 PM.

[totalshell]

some quick snaps from the garage this evening please bear in mind that bike is used at least 40 times a year and was in use yesterday so it needs cleaning and some maintenace but the fotos should give you an idea (clearly i cant ride or take photos but hope they are of some use)




ps the rust is the water that i washed the bike with at the trial. as i had to wait for my missus to pick me up i shelteredv in the bucket of an ackerman from the hail and sleet. to make the bucket 'habitable' i used an old bucket to scoop out the 100 litres or so of rainwater that had accunulated and rusted in the digger bucket (probably, definately the first wash since october fro the bike)

Edited by totalshell, 03 January 2007 - 12:34 PM.

[Subira]

You could go down the complete 'fiddle' route of using TY Mono forks with a bit of machining here and there - I figured that the rest of the bike is trick, why should the forks be any different

This previous post on the Macdonald frame might be of interest, good pics of a heavily modded, highly competitive cub.

http://www.trialscentral.com/forums/index....=3632&st=15

Edited by Subira, 03 January 2007 - 09:20 PM.

[oranagamcs]

Still have not decide what to do about the front end yet. I put in a email to Serco, I suppose I will call them or Allan Whitton soon. I went ahead and ordered some foot rests and swing arm from Samy Miller. Figured I might as well get started on the back half of the bike. One question though. Someone told me that you have to offset the engine to run the Miller arm, is this true? Its no big deal if I have to.

[totalshell]

martin adams has emigrated this month to Aus.

[Old trials fanatic]

Yes he actually goes later this week i think but has sold his business including premises to a new owner. Dont know anything about the new owner as yet except that for the short term the apparent intention is to continue as normal.

What happens then is anybodies guess.

Lets hope it carries on as previous but if not then i think most people will know where to go just have to wait and see.

If anybody knows any more please keep everybody appraised especially with the Scottish Pre65 classic only effectively 3 months away

[BOSTIT]

Knew Martins' emigration was on the cards, does anyone else do a 250 conversion? or will the new owner be offering them? any idea of cost?