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Bultaco Sherpa Hubs In A C15


hencam
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Many years of collecting and riding Bultacos means my father and I have number of relined/rebuilt Sherpa wheels, the later type single sided not full width. we are currently building a couple of Pre-65 C15 trials bikes that we hope to compete on in the Pre-65, Pre-67, Pre-70 what ever the class is that the all the other C15's on the day are entered into. the engines are C15G, so 1966ish, they will hopefully have B25 Alloy barrels fitted. One will be in a Drayton frame, one will be in a modified WD B40 frame, both will have forks with spindle mounted underneath, not leading axle.

We normally ride in the south and south west ACU and AMCA, if we fitted the Sherpa wheels, (i can skim the ribs off if required so they would look like a Rickman), this is for ease of having all bikes with the same wheels and only having to keep one type of shoes, Sprockets, ease of swapping, affordability, and the fact they are a nice looking wheel, would we be able to use these wheels without offending anybody, breaking any rules that others have not already broken. They are accepted in Pre-65 Motocross along with Grimeca, Maico and all other manner of hubs, i have also seen many other non pre-65, non British hubs in the pre-65 class at the trials we normally ride in.

help suggestions gratefully received, i am not trying to start a debate :rolleyes: , neither am i holding a giant wooden spoon !!

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I have a Sherpa rear wheel in my BSA which has a Faber frame. I'm assuming the width of the swingarm on that is going to be very much the same as a BSA and Drayton item. The problem you'll face id getting the wheel far enough over to the left for the chain run. With the boss on the Sherpa brake plate it will push the wheel too far to the right and the sprocket will be way off line with the engine sprocket. I machined the boss right down, even taking a bit off the face of the brake plate itself in order to get the sprockets to line up. This meant countersinking the bolt holes in the sprocket to use countersunk bolts as it runs so close to the swingarm normal bolts will foul it. The rim offset had to be moved about 10mm to the right from standard Sherpa offset if I remember correctly due to the wheel sitting closer to the left hand side of the arm than it does in a Sherpa.

Next problem was the brake arm as this now fouled the rear of the swingarm if the wheel was forward by a certain amount. In the Sherpa, it sits slightly inboard of the swingarm due to the boss on the brake plate so it's not an issue, but with that machined off it became a problem on the BSA. As the spline exits the brake plate at around 2 o'clock (due to the position of the torque arm stud in the plate) it sits just on the upper rear point of the arm. My solution was to take some metal from the top of the arm above the spindle, angling it down towards the rear to stop the brake arm fouling. Not much room to play with but you have to ensure you can move the wheel forward in the spindle slots and not have an issue. I guess if you're able you could reposition the torque arm stud in the plate to allow the brake arm to be position elsewhere but that was beyond what I can do. You then need to make a torque arm to fit. As there is no spacer on the sprocket side it just needs a spacer made for the other side and that was it.

I had thought about fitting a spacer behind the sprocket, moving the sprocket over, not the entire hub which would mean the brake plate wouldn't need shaving down and the brake arm may not be an issue. But I thought it would look odd as there would be a distinct step from sprocket to brake plate, so I never tried that.

I have a Grimeca wheel in the front as opposed to a Sherpa but that was a doddle to do compared to the rear, just needed to make spacers and to sleeve the brake plate and bearings for the 12mm spindle as I have Ossa forks.

As to whether it's acceptable or whether you'd offend anyone, I doubt anyone would bat an eyelid. Like me you've done it out of practicality and cost and used stuff you already have. There is no real difference in doing what your doing from using new billet machined parts and anyone who thinks there is because they aren't British hubs must have their head stuck far enough up their backside that they've lost touch with reality

This is the only picture I have of my back wheel, none of the other side unfortunately. Is it really so different from a billet hub?

post-71-0-02253700-1422831151_thumb.jpg

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As to whether it's acceptable or whether you'd offend anyone, I doubt anyone would bat an eyelid. Like me you've done it out of practicality and cost and used stuff you already have. There is no real difference in doing what your doing from using new billet machined parts and anyone who thinks there is because they aren't British hubs must have their head stuck far enough up their backside that they've lost touch with reality

:agreed:

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Thankyou Woody for a once again logical, down to earth answer, that is a very nice looking C15 you have there, is it a tubless rim?.

My decision is based out of practicality, to be honest i have no desire to, neither do i have the ability to ride in any championship. particularly as i would end up riding against a lot of people who can afford to disguise their mods by fitting Jap or European inners in there british fork bottoms etc, i like polished alloy, but can't afford alloy billet cub hubs, and this i would find frustrating if i was put in a different class because i cannot afford to disguise it.. that said i have no issues riding in a specials class and rules are rules. When i first ventured back to classic trials in the Somerset area i remember watching the 'Hand' brothers ride their immaculately prepared Tiger Cubs that are equally beautifully engineered. instead of riding in the pre-65 or what ever it is called now they road twinshock 'A' and still invariably won the trial.

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Yes, tubeless rear rim, bought a used GasGas wheel for about £45 and prayed the rim wasn't rotten. With the exception of the engine, which is a scratch built long stroke 340, the bike was built using mainly stuff from the shed I already had. The frame is a Faber MK3 which was £580, not the best frame available but for that price a pretty reasonable compromise. It is a light frame.

Rear hub I had relined £45, rebuilt into the rim with new spokes, about £80. Front wheel is Grimeca and I machined off the fins and rebuilt with new spokes, again about £80. Forks are spare set of Ossa I had. I chose not to run oil in frame and had a mate build the oil tank and the airbox. If I'd run oil in frame and used a foam filter the oil tank and airbox costs wouldn't have been incurred. Originally I used a spare set of Marzocchi yokes I have but wasn't sure about the offset so bought a pair of Alan Whitton's which have some rake built in rather than the usual parallel option

The cost of that to get a rolling chassis, no engine, was about £1500. If I'd used the Marzocchi yokes and not had the oil tank and airbox built I could knock £4 - 500 off that.

If I'd then used a normal C15 motor, like the type I had in my old bike instead of the long stroke, I could have rebuilt it for around £600, using normal road gears and cam, standard head, iron barrel. Add on ancilliary costs such as tyres, tubes, bars levers (new bars, expensive domino levers)

So by using the Faber frame and as many parts as possible from spares in the shed, the bike could actually have been built for under £2000.

That's saved over £2000 by not using new hubs, brake plates, rims, fiddle forks

And that exercise in economics and practicality makes it a special in some quarters

Takes all sorts...

As for yours, like I said, I don't think you need worry about anyone picking flies where you'll be using it. 98% of clubs take a more pragmatic view than the odd couple.

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This is my old one which had an original 1959 frame and '62 engine. Also considered a special and not allowed back to Scotland after I rode the 2 day on it some years back. Quite how they considered it inelligible when at the time it was parked next to a couple of brand new Cubs using all new parts was lost on me. The term and meaning of replica was also lost on the organiser...

'tis a funny old world we live in

post-71-0-35343800-1422920247_thumb.jpg

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Hi Guy's

Don't give up on the Beeza, Dave.

Get it back out when the Sun shines,It will look like a whole New ball game then.

Still think you should ride it in the "Manx Classic two day"?? Just say Hello to the Fairies as you cross that bridge, and you never know you may get that Win that has been eluding you.

The two bikes are and were a credit to the owner!! but I would say that!!!

Regards Charlie.

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