old trials fanatic Posted October 26, 2011 Author Report Share Posted October 26, 2011 (edited) Not read this thread in full but just posting this on behalf of my Dad who wanted to show how it can be done.... Correct me if i'm wrong but it appears he machined off the leading axle and then machined a couple of sleeved adaptors and shrunk them on ? Nice work very nice work so how does it handle? what about the front mudguard / exhaust/ front downtube issue? It's an earlier model than mine so the head angle may not be the same so there might not be a problem? Notice also the modified footrests which i have already done too. Edited October 26, 2011 by Old trials fanatic Quote Link to comment Share on other sites More sharing options...
mrb505 Posted October 26, 2011 Report Share Posted October 26, 2011 Strange my M49, standard set up, just touchs the mud guard on the exhaust under full fork compression while turning left, has your Dads bike got a tighter header pipe bend ? As my mudguard looks to be closer to the wheel than your Dads mudguard my M49 Quote Link to comment Share on other sites More sharing options...
feetupfun Posted October 26, 2011 Report Share Posted October 26, 2011 It does look like the header pipe has a tighter bend Quote Link to comment Share on other sites More sharing options...
pschrauber Posted October 26, 2011 Report Share Posted October 26, 2011 Thank you for the explanation of the tiller effect the sailboat comparison was already very easy to catch, (the half of my familiy are going to sea, I work on land but doing sailing already as a small kid). To the position of the handlebar to the axis of the headtube or the fork axis, this can be in my personal experience much better changed by the position of the handlebar. Maybe I'am not sensetiv enough to feel a big difference, if I turn to the right I move the lever in the right direction and it works very well . The main point in my view is to have as less overrun (Nachlauf in German or may be after run in English?). My doubs I have when the frontaxle is positioned in axis of the fork, that this position eliminates one of the big evolution steps in trials or bikes technical improvements: the shiftet position of the front axle. This reduce the overrun or afterrun (Nachlauf) and as less "Nachlauf" you have as handier is steering overal which is essential in trials IMHO. I don't know if I have used the right word, here a pic: Pic 3 variation of n due to the position of the front axle, Pic 4 variation of n due to the angleof the axsis of the headtube or fork. How n is changing due to the effect of a compressed fork: Standard diamentions of a gasser: I believe that maybe the steering of oldfanatic's Bulto might feel so bad because the fork doesn't respond so well anymore while turning. The terrain is rarly flat while turning and every small stone or pit that is not smoothed out by the forks suspension makes steering uncomfortable. There might be some different reasons for bad fork action: The fork just sits a little bit upthight in the clamps, The fork stanchions might be just a little bit bent, (a differenc of 2 - 3mm is not detectable by normal view, only if you deassamble the stanchions, but can worsen fork action). The lower forktubes might be weard out, sadly the stanchions are guided in the alloy lower forktubes without replaceable bushings, with the time, these lower fork tubes wear out and the cylinder hole inside them begin to get an slightly oval shape. And probably stiffend oil seals. Maybe just a really good and complete fork overhaul will fix the problem, nothing is build to last and work perfect up to the end of the world. Quote Link to comment Share on other sites More sharing options...
woody Posted October 26, 2011 Report Share Posted October 26, 2011 The English for Nachlauf = trail Quote Link to comment Share on other sites More sharing options...
sherpa325 Posted October 27, 2011 Report Share Posted October 27, 2011 I have been watching this thread for a few days now and I am still curious as to why? If you don't like the rear set handlebar position of the bultaco, I have seen several sherpas that have had the top triple clamp modified to move them forward, but to try and change the leading axle forks to inline forks has got me stumped. Every modern bike has leading axle forks, even Yamaha went to leading axle forks with the monoshock in 1984. A bike with inline forks will have a larger offset of the forktubes to compensate for the change in trail.My point is that you shouldn't change the legs without changing the triple clamps otherwise you are running a combination of both set-ups and I seriously doubt if it will work. Also on a bultaco there is no way that the mudguard is not going to foul on the downtube on full compression. As has been stated before most people I have seen who are having trouble on their twinshock, has been down to the bike being set-up poorly. Most commonly way too soft fork springs[very common on bullys] and too hard rear shocks. Bikes can be made to suit the rider by some very subtle tweaks in particular the handlebar height and the position for and aft has a huge effect on a twinshock. Also it cant be stressed how important time practising on the bike is. Just remember Bultaco won 5 world championships with three different riders with this fork and steering. Cheers Greg Quote Link to comment Share on other sites More sharing options...
yanski Posted November 12, 2011 Report Share Posted November 12, 2011 I think you should just sell me that 340 of yours . Bulto's ride well just has they were made ! Quote Link to comment Share on other sites More sharing options...
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