woody Posted December 24, 2009 Report Share Posted December 24, 2009 Don't overlook the fact that to use a DT360 piston, you have to open out the cranklcase mouth to take the bigger sleeve, fit a spacer under the barrel to get the correct port timing as the DT piston is of different dimensions (pin to crown height) and machine the head out to match the new bore size (I have no idea what needs to be done to the head but they are definitley altered on a 320 Majesty, you can't use a standard 250 head) You also need to open out a 250 head gasket to fit as there is no 'off the shelf' head gasket for a 320 - assuming the DT gasket has a different stud pattern. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted December 24, 2009 Report Share Posted December 24, 2009 Will the shock mount position on the D model that Frank is preparing be the same that on my A model that as never been modified?Guy A and D model frames differ in some minor ways but share the same geometry where ot counts so if you have the same extended length and compressed length on your shockies as Frank, you will be able to use the same top mount location. What is important if anyone is intending to move the top mount down to the same distance from the swingarm pivot as on the modified Yamaha frame Majestys, is that the top mount will then be much further from the top frame rail than on the Majesty frame so the bending moment on the frame tube at the top mount, will be much greater than on the Majesty frame. On the left side of the frame, a brace tube can easily be added to take the horizontal component of the load from the new top shockie mount, but on the right hand side of the frame, the exhaust is in the way of where you would want to fit a brace tube. I've seen some pretty strange bracing used to get around this issue, and have even seen one TY250 where the main exhaust section had been shortened at the back end to provide space for a brace. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted December 25, 2009 Report Share Posted December 25, 2009 Frank on page 4 of the magazine article at the below address, there is a side view of the rear end of the first model Majesty 250/320 (that was made by modifying a Yamaha TY250 frame) which could be scaled off to get the dimension from the swingarm pivot to the top shock mount. photohttp://www.tytrials.co.uk/trailandtrialsuk/cat_26578-Yamaha-Majesty-Specific-Parts.html David Quote Link to comment Share on other sites More sharing options...
ahamayfrank Posted December 26, 2009 Report Share Posted December 26, 2009 (edited) David, Thanks for the tip about the Majesty article. I have visited the tytrials site before but it is not extremely user friendly for me, so I never found the article. I have made some copies and I am going to see if the numbers make sense, as you suggest. Well into the adult beverages now having a day off and the rain still falling so should be a good evening for it. We have been having pretty typical UK weather a lot lately, if the rumors are true, so I should have some time in the bike shed tomorrow. I have been searching around the internet and found some additional photos including the ones here from oldtrialsfanatic and bodrinker with bikes with repositioned shocks. These two and the one in the article photos all have the swing arm lower shock mount farther rearward than the one on my TY. There are a number of photos modded TYs of different displacements (on the mijossi site for example) and quite a few different shock positions. Some have bracing at the top mount as Woody suggested and some don Edited December 26, 2009 by AHAMAYfrank Quote Link to comment Share on other sites More sharing options...
andy m Posted December 26, 2009 Report Share Posted December 26, 2009 Measurement on my Yamaha framed Majesty from centre of s/arm bolt to top shock mount ctr is 11 3/4" as near as I can see. Would be interesting to compare with OTF's std frame which has lowered mounts. Hope this helps. Quote Link to comment Share on other sites More sharing options...
ahamayfrank Posted December 26, 2009 Report Share Posted December 26, 2009 Thank's BD, I am headed to the shed with a pencil and a beer! Frank Quote Link to comment Share on other sites More sharing options...
guy53 Posted December 26, 2009 Report Share Posted December 26, 2009 Well guy's the more I read the more I'm puzzled, I have 2 434 frames and a b model in the shed all 3 of them with original shock ( 315 mm ), and same configuration. It seem that 340 mm shock is the thing to get, unfortunatly I have never been able to try a mod TY neither SEEN a modified TY much less a Majesty frame, here in Qu 1 Quote Link to comment Share on other sites More sharing options...
ahamayfrank Posted December 27, 2009 Report Share Posted December 27, 2009 Guy, I am not to be considered an expert on any of this, but I will tell you what I know, what I have learned, here as well as searching the internet, what I have discovered today, and my opinion. I have not seen any Majesty bikes here in the SE US either, and trials riding in general is not very popular, so this site Quote Link to comment Share on other sites More sharing options...
guy53 Posted December 27, 2009 Report Share Posted December 27, 2009 Thank's Frank, I have pirnted ALL the post to make sure not to lose any advise from you guy's. One question is the motor raised in your frame? Guy Quote Link to comment Share on other sites More sharing options...
b40rt Posted December 27, 2009 Report Share Posted December 27, 2009 Guy,I am not to be considered an expert on any of this, but I will tell you what I know, what I have learned, here as well as searching the internet, what I have discovered today, and my opinion. I have not seen any Majesty bikes here in the SE US either, and trials riding in general is not very popular, so this site Quote Link to comment Share on other sites More sharing options...
jon v8 Posted December 27, 2009 Report Share Posted December 27, 2009 I always thought it was more about ground clearance,the standard 250 is pretty low,and with a fairly wide motor it does feel like you are farmer out ploughing at times.Been following this thread with interest as I have two spare late 250's.Its always been at the back of my mind to convert one of them. Quote Link to comment Share on other sites More sharing options...
guy53 Posted December 29, 2009 Report Share Posted December 29, 2009 Ok guy's, here what is puzzling me : when you increase the rear wheel travel by instaling longer shock and/or moving the top anchor point does it change the balance of the machine, as I told before, I always tought that the front end of the TY was '' heavy ''. Guy Quote Link to comment Share on other sites More sharing options...
ahamayfrank Posted March 13, 2010 Report Share Posted March 13, 2010 (edited) http://xlforum.net/photopost/data/500/1977_TY250D_RH.jpg I tried attaching the above photo, but it is not allowed. If you are curious I guess you will need to endure a bit of a "Sportster" site. Spent a few weeks in the "Man Cave" and this is what came out. I am pretty happy with the result!! Frank P.S. New rear spring rate for the relocation, engine rebuild still at 250cc with fresh parts, paint here and there, and alot of love. Two trials on the maiden voyage to "bike week" were a success. Suspension much smoother acting and the engine is much crisper (flywheel, airbox, compression). Front rides a bit high but a great start. Tuning to continue!! Edited March 14, 2010 by AHAMAYfrank Quote Link to comment Share on other sites More sharing options...
marky g Posted March 13, 2010 Report Share Posted March 13, 2010 Cracking job, how does it ride? Quote Link to comment Share on other sites More sharing options...
guy53 Posted April 11, 2010 Report Share Posted April 11, 2010 If you install 340mm shock or move the top atachement to improve rear wheel travel, doyou make any change to the front fork? Guy Quote Link to comment Share on other sites More sharing options...
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