chris_ Posted February 22, 2012 Report Share Posted February 22, 2012 Sorry, some more newbie questions; Forks Will forks from a later 247 (1978/9) fit as a straight swap on my 1973 bike? One of my fork tubes is bent, and I am unsure whether to go for a later pair currently being listed on eBay, or to try to get mine straightened. There are mixed opinions as to whether or not it is worth trying to straighten a bent fork anyway (assuming that there are no creases). Rear shocks What is the correct size/length? I am fairly heavy (85-90kg depending on lunch) so what would be a suitable specification if I were to go for new shocks or springs? I am trying to work out whether it is worth rebuilding the old Telescos (which are totally worn out) or going for new. Speedometer Is the speedo simply a "bolt-on" job (assuming you have got all the parts) or are there differences in the forks or hubs between bikes that were supplied with speedos from new? I have looked at parts lists and diagrams but none of mine show the speedo parts? Thanks again Quote Link to comment Share on other sites More sharing options...
martin belair Posted February 22, 2012 Report Share Posted February 22, 2012 Hi Chris, are you sure the fork is bent and not just stuck? The reason I ask is that older Montesa forks can become stuck if the bike sits un-used for a long time. The bushing at the end of the damper rod "swells" and becomes stuck. If so, drain the oil, then unscrew the allen bolt at the bottom of the lower fork leg and pull the fork apart. The damper rod will be sticking out the bottom of the upper fork tube. Next remove the top fork tube nut and spring. If its is not stuck the damper rod will easily come out the top, otherwise you will need to push it out. I use an old broom stick and mallet. You will need to have the offending bushing turned down to re-fit. Quote Link to comment Share on other sites More sharing options...
chris_ Posted February 22, 2012 Author Report Share Posted February 22, 2012 Hi Martin, the forks move up and down freely, but one tube is bent back from the bottom of the lower yoke/clamp. I need to get it apart to confirm, but I am 99% sure just from looking. One leg is noticeably set back and distinctly banana shaped. Quote Link to comment Share on other sites More sharing options...
chris_ Posted February 28, 2012 Author Report Share Posted February 28, 2012 Definitely bent... Quote Link to comment Share on other sites More sharing options...
feetupfun Posted March 7, 2012 Report Share Posted March 7, 2012 Hi Chris, are you sure the fork is bent and not just stuck? The reason I ask is that older Montesa forks can become stuck if the bike sits un-used for a long time. The bushing at the end of the damper rod "swells" and becomes stuck. If so, drain the oil, then unscrew the allen bolt at the bottom of the lower fork leg and pull the fork apart. The damper rod will be sticking out the bottom of the upper fork tube. Next remove the top fork tube nut and spring. If its is not stuck the damper rod will easily come out the top, otherwise you will need to push it out. I use an old broom stick and mallet. You will need to have the offending bushing turned down to re-fit. I am in the process of getting my 348 working well and would like some advice about the issue with the plastic bushings in my forks. After reading Martin's posting I wondered of the problem I am having with my 348 forks might be caused by that same issue. My problem is that when the forks bottom they feel quite harsh in comparison with when the forks bottom on my OSSA MAR and Bultaco M49. The action of the 348 forks is otherwise fine. Tonight I tested the action of one 348 fork leg without the spring in it and it did stick a bit at the bottom end of the travel. I pulled that leg apart and the plastic sleeve seemed to be a neat fit in its mating part. I measured the clearance between the parallel sections of the parts at between 0.1mm and 0.2mm and the plastic sleeve is also slightly belled out on the bottom end. I then measured similar parts from a set of Bultaco Betor forks and the clearance between those parts was 0.5mm. I believe the function of these parts is to provide a hydraulic anti-bottoming function that is effectively very heavy compression damping that happens in the last 25mm or so of the fork stroke. Am I right in assuming that the clearance between the Montesa sleeve and mating part should be more like the 0.5mm that I found with the Bultaco forks? Note the Bultaco parts do not appear worn or damaged in any way and are both made from aluminium. The Montesa plastic sleeve mating part is made from steel. Quote Link to comment Share on other sites More sharing options...
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