August 25, 20188 yr my project currently has some 36mm jap forks in that are not really suitable for trials, I am planning to change to bultaco 35mm leading axle forks as I have access to some, my question is what type of yokes? cubs are non parallel with 1.5 degrees in the yokes as standard, but given that I am changing to leading axle forks should I be looking of parallel yokes to compensate for this change or would non parallel ones work without causing issues to trail/rake?
August 25, 20188 yr This does nto really answer your question but I ran bultaco leading axle forks with the Bultaco yolks on a BSA C15 and it turned quite nicely.
January 25, 20197 yr I recently got a 1961 tiger cub. Unfortunately the front fork comes from a Montesa. I would like to go to scottish pre 65 2 days trial. Which front fork can I get suitable for this trial ? I read something about marzocchi hydraulic fitted into an original forks ?... Thanks in advanced
January 25, 20197 yr Author I can t help you sorry but I am sure if you start a new thread you will get some help
January 25, 20197 yr 20 hours ago, EREM said: I recently got a 1961 tiger cub. Unfortunately the front fork comes from a Montesa. I would like to go to scottish pre 65 2 days trial. Which front fork can I get suitable for this trial ? I read something about marzocchi hydraulic fitted into an original forks ?... Thanks in advanced If you are not mega rich then most bikes have marzocchi forks with the alloy sliders turned down and fitted into Norton sliders. However when doing this the Marzocchi sliders become VERY thin so best to entrust the work to someone who is experienced at this modification. Gives a good front end when done and as you say is Scottish legal.
January 26, 20197 yr On 1/25/2019 at 12:23 AM, EREM said: I recently got a 1961 tiger cub. Unfortunately the front fork comes from a Montesa. I would like to go to scottish pre 65 2 days trial. Which front fork can I get suitable for this trial ? I read something about marzocchi hydraulic fitted into an original forks ?... Thanks in advanced Hi Erem, The 35mm Montesa fork legs from the 1970s Cota bikes are very suitable for your Triumph Cub but ideally need to be fitted into lower fork legs from Triumph, Norton or AS/Matchless these two brands use the same forks. The lower fork leg from the Montsa is slimmed down to fit into the type of fork you choose either Triumph lower legs which are steel or alloy AJS type then usually a joining piece to make up the gap between the two turned to suit. Best to find someone to do the machining work who has done this conversion before. If you can make it to the Telford off road show next month there will be people there who do this. The Triumph lower legs seem much harder to find than either of the other types, they weigh more and are slimmer internally so the donor legs have to be turned to a smaller diameter than needed for the other makes. Both Norton and AJS Matchless lower legs are I think being remanufactured. I think lots of the alloy lower legs about on autojumble stands were removed and replaced with new due to wear developing causing MOT test failure, this wear is unimportant though when another leg is fitted inside the worn one. As for yokes my preference would be 1.5 degree run out from these people https://villiersservices.co.uk/index.php?main_page=product_infoandcPath=83andproducts_id=295andzenid=mvt2bentf3hr71lhd9rqguvt24 when using straight leg forks. For leading axle then parallel might be best but for a British bike unless using Royal Enfield lower legs keep them straight with 1.5 yokes. ¥ Edited February 19, 20197 yr by trialsrfun
January 26, 20197 yr On 8/25/2018 at 1:26 PM, detective 21 said: my project currently has some 36mm jap forks in that are not really suitable for trials, I am planning to change to bultaco 35mm leading axle forks as I have access to some, my question is what type of yokes? cubs are non parallel with 1.5 degrees in the yokes as standard, but given that I am changing to leading axle forks should I be looking of parallel yokes to compensate for this change or would non parallel ones work without causing issues to trail/rake? 1 hour ago, trialsrfun said: Hi Erem, The 35mm Montesa fork legs from the 1970s Cota bikes are very suitable for your Triumph Cub but ideally need to be fitted into lower fork legs from Triumph, Norton or AS/Matchless these two brands use the same forks. The lower fork leg from th Montsa is slimmd down to fit into the type of fork you choose then usually a joining piece to make up the gap between the two turned to suit. Best to find someone to do the machining work who has done this conversion before. If you can make it to the Telford off road show next month there will be people there who do this sot of work. The Triumph lower legs seem much harder to find than either of the other types they weigh more and are slimmer internally so the donor legs have to be turned to a smaller diameter than needed for the other makes. Both Norton and AJS Matchless lower legs are I think being remanufactured. I think lots of the alloy lower legs were removed and replaced with new due to wear developing causing mot failure, this wear is unimportant though when another leg is fitted inside the worn one. As for yokes my preference would be 1.5 degree run out from these people https://villiersservices.co.uk/index.php?main_page=product_infoandcPath=83andproducts_id=295andzenid=mvt2bentf3hr71lhd9rqguvt24 when using straight leg forks, for leading axle then parallel might be best but for a British bike unless using Royal Enfield lower legs keep them straight with 1.5 yokes. ¥ Hopefully the above may help, good luck with your project.
January 26, 20197 yr One other thing. Leading axle forks on a cub would be a no no for Scotland btw. They dont even allow 4 bolts only 2 on Triumph fork legs.
January 26, 20197 yr 2 hours ago, old trials fanatic said: One other thing. Leading axle forks on a cub would be a no no for Scotland btw. They dont even allow 4 bolts only 2 on Triumph fork legs. OTF I think the Royal Enfield fork bottoms are accepted in Scotland at the two day I have seen them fitted to several bikes there.
January 26, 20197 yr As I understand any pre 65 fork would be eligible. I have friends using Royal Enfield leading axle forks in Scotland. I think Triumph/BSA 4 bolt forks came in 1971 together with the conical TLS front brake
February 18, 20197 yr On 1/26/2019 at 9:12 PM, carl ekblom said: 1,5 degree rake at the yokes equals approx 20mm offset at the front wheel axle Please forgive my ignorance... but do you mean it make it 20mm longer between axles?
February 19, 20197 yr If Bultaco 199A have had parallel yokes the trail would have increase from 70mm to 90.4mm. Bultaco Sherpa yokes have 1.5 degree rake. I also have a 199B. It has a steering angle of 27degrees As far as I know modern bikes have parallel yokes, approx 60mm offset and a steering angle of 20-22degrees. 199A has 24.5degree steering angle and a total offset of approx 80,4mm (result is strange steering)
February 19, 20197 yr 20 hours ago, EREM said: Please forgive my ignorance... but do you mean it make it 20mm longer between axles? 4 hours ago, carl ekblom said: If Bultaco 199A have had parallel yokes the trail would have increase from 70mm to 90.4mm. Bultaco Sherpa yokes have 1.5 degree rake. I also have a 199B. It has a steering angle of 27degrees As far as I know modern bikes have parallel yokes, approx 60mm offset and a steering angle of 20-22degrees. 199A has 24.5degree steering angle and a total offset of approx 80,4mm (result is strange steering) If you look at the two lines on the left picture posted by Carl you can see that the space at the lower end is greater than at the top this is where the 20mm comes from.
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