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Is It Worth "modifying" A Std Ty Frame To Majesty Spec?


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  • 2 years later...

I am new to this site and to had to the pleasure !!! I am a french Canadian, so please forgive me for amy wrong spelling or maybe using the wrong term. I was reading the post on putting a DT 360 piston in place of the 70 mm std, do you have to install a DT :biggrinsanta: sleeve in place of the original one, and also I have heard that they use the same 26 mm carburator is it ok?

I am planning to replace the original carburator, I whant to install a VM Mikuni, am I going in the rite direction.

I have been out off the trial world for 3..some75aaebab35af9c8d3975e2dc20c91d8f

years.

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To use the DT360 piston, you make a new, bigger sleeve to fit into the TY250 barrel.

If you use a DT360 barrel, the port timing will be wrong because it the DT360 has a longer stroke than a TY250.

26mm VM Mikuni carby is good for a 320cc TY250 motor

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This is my first post in the Yamaha section, just a lurker up to this point I guess. Almost 2 years ago I purchased a 1977 TY250D US spec model. It had quite a few updates to it such as progressive fork springs, tapered head bearings, updated carb and exhaust, and Falcon shocks. I have been

Edited by AHAMAYfrank
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This is my first post in the Yamaha section, just a lurker up to this point I guess. Almost 2 years ago I purchased a 1977 TY250D US spec model. It had quite a few updates to it such as progressive fork springs, tapered head bearings, updated carb and exhaust, and Falcon shocks. I have been
Edited by feetupfun
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You need to bear in mind as well that the modified Yam frame version of the Majesty (ie; the original Majesties) had a fair reworking of the entire rear subframe and engine cradle, not just a case of repositioning the top shock mounts. Whilst that alone will probably improve the TY suspension, it isn't going to put it on a par with a Majesty.

The front frame downtubes were shortened by almost 2" and the rear of the frame altered to match. How they did this I don't know, I've had a Majesty Yam frame and standard TY frame side by side and although I can see the difference, I can't see how it was done. Very clever though as the rear suspension on the Majesty, with decent shocks of course, is close to the best twinshock rear suspension setup I've ever tried.

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David and Woody,

Wow you guys are really into this. Great information!! Trials in the US and especially Twin Shock Trials is not popular at all. We have a few old farts (myself included) that seem to be the core, riding modern and vintage bikes, but still a very, very small sport here in the southeast US.

I worked at a Yamaha dealer in 1977 so the TY250D may be the first Trials bike I ever rode so thus my choice. I would like to use mostly Yamaha parts but get my bike to work as good as I can so a full Majesty mod is not what I am interested in. Well I may actually be interested, but he frame prices I have seen are quite high. Honestly I have only started to understand the history of the

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Sorry Frank not that simple because the Majesty frame based on the TY frame has the frame uprights shortened so a measurement from the top rail is dodgy unless you shorten your uprights exaxtly the same and don't change their angle. I reckon if you are not doing the mods to the main frame only shockie mounts, you need a measurement from the swingarm pivot to the top shockie mount to get the shockie angle right and then position your mount to give clearance to the rear guard and see how far down the swingarm goes. I suspect you falcons will be 4" travel which will probably generate problems ie the swingarm will go too low and/or too high, because the original shockies would have been 3.25 to 3.5" travel. I notice some people have bent up the rear fframe loop on theirs to get around this problem.

I can only tell you that measurement for Godden Majesty, which may be different to a modified TY250 frame type Majesty. I'm sure there are people with the Yamaha based Majesty frame that read this forum though.

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If you bear with me for a couple of days I will measure my Yam framed Majesty. I have one waiting for a rebuild which is currently shelved in storage. I have a pair of new Falcons fitted to it so can measure it. Here is a taster pre rebuild.. :biggrinsanta:

Also you will notice the forks are later mono ones

post-2285-1261587841.jpg

Edited by bo drinker
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Many thanks for the info.

I am reading Frank's questions and the reply, and I am very interested since I am preparing a 434 model for this spring: engine done (new rod kit, piston, ring, bearings and seals ) no autolube that Mikuni carb mention earlier, footrest repositions , the 360 DT piston job will be the next fall project.

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

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