steve fracy Posted November 28, 2014 Report Share Posted November 28, 2014 (edited) How about we try and turn this into something constructive, We know about the gear mechanism being weak but this only appears to be a problem with crashing or being ham footed with it so I assume this is not reliability issue just a weak part that needs to be taken care of. The gearbox bearings, I understand that the split needle rollers are the culprits for failure, So is it a particular one that gives up? What exactly causes them to give up? Is there a way of finding heavier duty or better quality replacements? There is a wealth of knowledge from members on here, Dadof2 and Nigel have excellent knowledge, They know their stuff, but have rattled each others cages and I can understand both sides of this Plus it has been a bit of entertainment too! What we need to know is why do they shed bearings and also why do some seem to go on forever? Are serious about a wealth of knowledge from DO2? Just because anyone is free to say what they want, doesnt mean its fact. He lost me on another thread where he declared the Bultaco and the TY350 are the best trials engines......yikes! What decade are we in now? Edited November 28, 2014 by steve fracy Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted November 28, 2014 Report Share Posted November 28, 2014 I do not have any great wealth of knowledge. I see what has worked for me and the only knowledge i have of any consequence is that all makes have faults of varying degrees and even 4rt's arent faultless. ...and 90% of reliability issues are down to owner. Note to self ~ avoid slippy becks. Quote Link to comment Share on other sites More sharing options...
leg over Posted November 28, 2014 Report Share Posted November 28, 2014 Who is slippy becks? Quote Link to comment Share on other sites More sharing options...
dadof2 Posted November 30, 2014 Report Share Posted November 30, 2014 "Are serious about a wealth of knowledge from DO2? Just because anyone is free to say what they want, doesnt mean its fact. He lost me on another thread where he declared the Bultaco and the TY350 are the best trials engines......yikes! What decade are we in now?" Some people clearly need to learn to read properly, the above is not what I wrote which was 1979 325 Bultaco and last of the TY250 air cooled monoshock Yams are my favourite engines A beck is the northern English term for a small river. The Pro gearbox is almost certainly the most unreliable ever fitted to a trials bike (and probably any motorcycle), since the 1970s anyway. Quote Link to comment Share on other sites More sharing options...
gasgas249uk Posted November 30, 2014 Report Share Posted November 30, 2014 And..........were off again 4 Quote Link to comment Share on other sites More sharing options...
breagh Posted December 1, 2014 Report Share Posted December 1, 2014 That was a read. Said it before some of the riders out there would break an anvil ! Until someone in the UK starts producing a decent trials bike we're on very shaky ground knocking any make of bike. Got to be realistic ,modern bikes wont stand repeated heavy use (abuse),that's the way it is. They're not meant to last forever,they're competition bikes. Personally i find the bikes a lot more reliable than the riders. 1 Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted December 1, 2014 Report Share Posted December 1, 2014 ......and breathe. 1 Quote Link to comment Share on other sites More sharing options...
b40rt Posted December 1, 2014 Report Share Posted December 1, 2014 They're not meant to last forever,they're competition bikes. Your about to find out ! Quote Link to comment Share on other sites More sharing options...
dadof2 Posted December 5, 2014 Report Share Posted December 5, 2014 "to post or not to post, that is the question?" (slight deviation from the original) And here is a Shakespeare quote he probably would have uttered regarding both GG Pro and Ossa gearboxes "a curse on both your houses" And to correct a misquote by ND, I wrote "several", ND misquotes this as "a couple". In this case my use of several referred to at least 4, probably 5, not 2 A large proportion of the Pro gearbox failures cannot realistically be attributed to rider misuse. The Pro gearboxes have failed in the hands of riders who have ridden many other makes over many years and other than the pro they never had a single gearbox failure. It is clear from 249s interview that the GG and Ossa gearbox designer favours part number and weight reduction over longevity and that is what he possibly has to do to make the bike competitive at the highest level. Clearly some riders like or at least satisfied with this, but there are also a large number who would like to return to TY 250 monoshock levels of reliability. Quote Link to comment Share on other sites More sharing options...
dadof2 Posted December 5, 2014 Report Share Posted December 5, 2014 Steve Earl wrote / asked "The gearbox bearings, I understand that the split needle rollers are the culprits for failure, So is it a particular one that gives up? What exactly causes them to give up? Is there a way of finding heavier duty or better quality replacements?" For about 15 years a portion of my work was design of machine tools. These were generally expected to run 20 to 22 hours a day for a minimum of 5 days a week, We simply would not have used a split cage needle roller bearing because failure was near certain to occur much earlier than a bearing with a one piece cage or a crowded bearing. Any bearing manufacturer will tell you this. This split cage type of bearing is very sensitive to wear or variance from ideal lubrication. With slight wear, poor lubrication or different loading at different points along the bearing, the rollers start to slew and their axis of rotation is no longer parallel to the axis of the "races" which enclose them. This causes skidding, high localised loads and the situation goes from bad to worse. Heavy duty - increasing the roller diameter will likely worsen the situation. The failures are unlikely to be a material quality problem. The cost of improving the bearing by finer tolerance would probably be prohibitive and may not work. 1 Quote Link to comment Share on other sites More sharing options...
sherpa325 Posted December 6, 2014 Report Share Posted December 6, 2014 If you have read all of the fantastic interviews that gasgas249uk has put up, it is pretty obvious that we are very lucky to have a core group of Spanish and to a lesser extent Italian enthusiasts who are willing to produce Trials Bikes for us to buy. Without them I doubt we would have a sport at all. They continually put their money and expertise into producing some fantastic bikes that are cutting edge in design.They have been doing this since the seventies. What we can buy from these European companies is pretty much what the top guys rode in the World Championship the previous year, I don't know of too many other sports where this happens. The bikes are lighter and the power delivery gets better and better as does the whole package. On the flip side I cant begin to get my head around how you can produce such a quality product in such limited numbers. How much bargaining power do you have when only ordering two thousand custom made ignition systems, or rear shocks, or forks, or shafts and gears for the gearboxes.I would imagine its very difficult to keep a reasonable price on the components and also provide the service that is expected with such a small production run. These are not large multi national companies with infinite resources [they are not interested in our sport] they are small companies chasing a dream with very little chance of achieving a decent financial return. I just hope they keep on doing it, all of them. PS If I had to go back to a TY mono motor I am pretty sure I wouldn't ride, definitely the worst performing trials motor I ever owned Cheers Greg 4 Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted December 6, 2014 Report Share Posted December 6, 2014 Sound views Greg, and if d of dick wants to read and digest he may well realise talking about trials gearboxes in one breath and machine tools running for 22 hours a day may be slightly different? We are forever optimistic. Your point of 2000 units a year may be the case for gas gas and the other popular makes but I doubt the newer and more recent manufacturers are anywhere near that in totals. perhaps then if we are realistic (d off excluded) failures of some is not surprising. Quote Link to comment Share on other sites More sharing options...
dadof2 Posted December 9, 2014 Report Share Posted December 9, 2014 Sherpa 325, I am a bit surprised at your dislike of the Yam engine, in various forms it powered the Scott trial winner 11 times in between 1984 and 1998, a pretty good record by any measure. It may not have been the best engine for top flight riders but for the clubman it provided extremely reliable service and hardly even needed the oil changing. Back to split bearings - Vehicle bearing manufacturers have tried many times to make split rolling element bearings as they have better friction characteristics than plain bearings, but so far no split rolling element bearing has been produced that can match the performance of non split bearings. For example on a Suzuki 1100 GSX they went to the trouble of pressing together all the crankshaft parts so they could use non split roller bearings. The Burman gearbox of the 1950s used cageless crowded roller bearing and these were very robust despite being lubricated with a mix of grease and paraffin. Perhaps GG should slightly redesign the shaft and use crowded instead of caged rollers. Crowded rollers have the advantage of spreading the load over a greater area, but have less space for lubricant ingress so may not work as well at higher RPM. It is very difficult to know why these bearings fail on a GG. When they fail it makes such a mess you can't tell how the failure initiated and when you strip a gearbox to sort the selector failure you don't see any obvious precursors to the split bearing failure. Quote Link to comment Share on other sites More sharing options...
steve fracy Posted December 9, 2014 Report Share Posted December 9, 2014 Which Ty engine exactly are you referring to that you love so much? Quote Link to comment Share on other sites More sharing options...
atomant Posted December 9, 2014 Report Share Posted December 9, 2014 Don't feed the troll .... 1 Quote Link to comment Share on other sites More sharing options...
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