August 10, 201412 yr Just the stem? Can't see how this helps as the yokes have the rake built in, or do you mean the entire yoke assembly from the Alpina / Pursang (only certain years work) They are parrallel as opposed to the anngled Sherpa yokes but the spacing of the forks is wider which means new spacers have to be made for the front wheel and I'm not sure how the Sherpa mudguard brace will cope with the extra width. I think the lock stops may present an issue too. I was going to try it not too long ago but didn't bother in the end as the hassle wasn't worth what would have probably been a minor and barely noticeable improvement Ok, so i think i am starting to understand????? if the stem is parallel to the stanchions it steepens the fork angle, i think sherpas are normally leaning in about 1.5° at top, i would have though putting the stem in parallel would have increased the rake and made the steering shallower. so if i machine up a new pair of billet yokes with a stem running parallel to the stanchions it will make the bike react slower because the trail is increased, i assumed it would steer quicker. or am i completely missing the point and when people talk about parallel yokes the are referring to the stanchions being in line almost with the stem if looked at from the side on view instead of sitting in front of the stem by 'X' distance. i don't really have a problem with my sherpa steering, i am not competent enough a rider to be able to worry, however as i like making nice parts for my bike, which is where the pleasure comes in if i can improve it, it would be nice?? can somebody please explain in an easy to understand way
August 11, 201412 yr Yes parallel yokes have the fork tubes parallel with the steering stem. You can change the trail by changing either the angular offset of the fork tubes, the linear offset of the fork tubes (your X distance), the amount of axle offset or even the steering rake angle or any combination of them. The geometry of the fork tube holes in the standard Bultaco Sherpa T yokes is very good for trials. If you fit late model Alpina yokes, the trail dimension will be increased (heavier steering at standstill). The most common thing people do to modify Bultaco steering geometry is to steepen the rake angle. This can be done on a Sherpa T by lowering the front of the bike, raising the rear of the bike, or doing a frame chop. Making the rake steeper has the effect of making the steering lighter when the bike is stationary, but loading the steering up more in riding situations when the trail goes negative. Works racing (MX and Road Racing) bikes have adjustable steering rake angle using eccentric sleeves inside the steering stem. That would be a pretty cool modification that would allow you to experiment with rake angle to see what suited you best
August 12, 201412 yr Just the stem? Can't see how this helps as the yokes have the rake built in, or do you mean the entire yoke assembly from the Alpina / Pursang (only certain years work) They are parrallel as opposed to the anngled Sherpa yokes but the spacing of the forks is wider which means new spacers have to be made for the front wheel and I'm not sure how the Sherpa mudguard brace will cope with the extra width. I think the lock stops may present an issue too. I was going to try it not too long ago but didn't bother in the end as the hassle wasn't worth what would have probably been a minor and barely noticeable improvement Just the stem? Can't see how this helps as the yokes have the rake built in, or do you mean the entire yoke assembly from the Alpina / Pursang (only certain years work) They are parrallel as opposed to the anngled Sherpa yokes but the spacing of the forks is wider which means new spacers have to be made for the front wheel and I'm not sure how the Sherpa mudguard brace will cope with the extra width. I think the lock stops may present an issue too. I was going to try it not too long ago but didn't bother in the end as the hassle wasn't worth what would have probably been a minor and barely noticeable improvement Yes, the whole yoke, axle and spacers. Quite a common mod in the western U.S. I`ve never done one myself, but I`ll try to find some pics.
August 12, 201412 yr Yes, the whole yoke, axle and spacers. Quite a common mod in the western U.S. I`ve never done one myself, but I`ll try to find some pics. Yes, I understand that, I've seen it done and was going to do one myself, just wasn't sure if you meant the stem only.
August 24, 201412 yr Author 200cc is too much for the Bultaco forks, you'll lose travel through hydraulic affect, but it's up to you if you want to continue with it. Fantic forks only use that and they are over 2" longer, plus, look how short the Bultaco legs are. They are basically the same fork as the Ossa but the Ossa had longer legs and the most they take is 180cc. I mentioned why they may be topping in my previous post, and the affect of fitting different forks, all of which are longer. Dont think I'm losing any travel ;-) Edited August 24, 201412 yr by taff_d
August 27, 201411 yr Author Done 2 more trials on it and had all sorts of trouble with the front end bottoming out (see picture in post above), so I have stripped the forks completely and for a 37 year old bike they are not bad at all internally the left leg is better than the right. I checked on the price of HFS expert suspension and it was £205 much more than I wanted to spend on a bike I will only ride occasionally, they never got back in touch with a price for the clubman setup ??? Magical seem to have disappeared up their own a%*e so thats a no go, so I had a long chat with Inmotion and I've ended up buying new Pursang springs with adjustable preload spacers, they reckon to start at minimum preload and 180cc of 20w oil and work up from there to a max of 200cc oil and play with the preload. If this fails I have a mate who has a set of 38mm Betor forks and yokes I'll try to fit and see how they go.
August 27, 201411 yr hi have used both magicals and persang springs and both are good am 16.5 st so not the lightest rider but there ok for me. with 180ml off 15W
August 28, 201411 yr Author springs arrived this morning, so the set up is new Pursang springs, 180cc of 20w oil and 10mm of preload and it feels a different bike have only ridden it up and down the lane tried to do a few stoppies but could not get it to bottom out, does not dive anymore on the brakes and seems to turn better will go for a practice Saturday.
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