OzVMX Forum
Marque Remarks => Yamaha => Topic started by: Tahitian_Red on June 02, 2012, 05:51:08 am
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I'm thinking of lengthening my stock 1970 DT-1 swingarm. It is the square tubing type. (our "stock class" rules allow adding 1 inch to the stock swingarm, no aftermarket or other model arms allowed)
:(
Would it be best to add length to the flat axle mount pieces or at the the tube sections in front of the shock mounts?
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I'm not sure on whether the DT-1 swingarm has a section of the tubing that is parallel to the wheel or not, if it doesn't you'd end up with a wider arm by adding your length there which would throw out shock alignment etc as well as changing the position of the shock mounts on the arm
Personally the flat plate would be easier, you could trace out the shape of the flat plate then add in your required amount & have new plates made up before removing your old ones which should be the strongest method
Lengthening TY175 swingarms is quite common & Feetupfun has done a good job of explaining how it's done here
http://www.trialscentral.com/forums/topic/34503-lengthening-ty175-swingarm/page__hl__%2Blengthening+%2Bty175+%2Bswingarm__fromsearch__1
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i did a DT1 swingarm a while back and cut the old plates out, fabricated the new longer ones and then welded them in.
it seemed the easiest option to me. the bike is no longer in my possesion and i have no photo's of it either.
sorry bout that...
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Can't you find an RT1 arm?
They are a bit longer I believe.
pancho.
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Pancho,
'71 DT-1 same as '70-71 RT-1, but '70 DT-1 is different. (bolt, bushings and collars all different parts)
It would have been an easy fix.
:(
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Back in my Mooebank days I got hold of a 250 Jawa road bike wth 16 inch wheels and the swinging arm needed to be extended to accomodate a 19" rim, so un-subtle me cut the arm, found a piece of handlebar hammered in quite well and then bronze welded in place did the job!
Actually didn't look to horrible with a bit of paint over it!
With a bit of engine work I found that the whole F******* adventure was a total frustrating episode what with no guts and endless battles with PAL elecTRICKs. Plus it tried to do me in at Sorbent Hill by blowing a cranckase seal at a critical time!
pancho.
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Because I worked for the government and had TIG and MIG welders and a plasma cutter at my disposal as well as the time and and a sympathetic boss allowing me to do it as a foreign order I spent a lot of time lengthening mine by extending the rectangular tube section 2" behind the shock mount. By adding the length behind the shock mount the suspension mounting points remain in their original place keeping the rule Nazi's happy. One offshoot from extending behind the shock mount is that rear travel is increased, something I hadn't considered until the bike was protested at the first Cherabah Nats. After checking, the travel came in at 4.25" using 14" Curnutt shocks. The scrutineers on the day dismissed the protest as "frivolous", deeming a quarter inch over didn't make me a cheat.
I used a section of 2" x 1" square tubing for the job, and two 2" lengths of flat 1/8" plate to slip inside each wall of the swingarm and new tubing to act as internal sleeves. I then carefully cut out the axle flange and fitted it into a slot in the new tube section. In the end it was a lot of work involving making a wooden jig to keep it all straight. The job took me about 10 hours and If I was to do it again I'd do it the same as Vandy did, a much simpler, lighter way of achieving the same net result.
I'd take some photos of my swingarm but the bike's in storage under a pile of crap which puts it in the too hard basket right now.
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Vandy was that the bike you sold to me ? if so I can get photos for you . Iain
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that'd be the one Ian.
funnily enough that swingarm origionally came from Freaky.
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hey dont drag me into this sorded mess.......
i just ride the bloody things
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So, I'm going to make a Freaky built, Vandy ridden, Ian owned, replica swingarm? This is getting convoluted.
Are you sure Firko wasn't involved somewhere in the process?
;D ;D ;D
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so that'd be an "ex Freaky, Vandy modified, Firko inspired , Ian owned, Tahitian Copied swingarm then?
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Yes! LOL
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Modification to YZ250B (modern Cycle March 1975)
(http://i427.photobucket.com/albums/pp359/vintage_addict/Share/yz_swignarm_extend1.jpg)
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Are they extending that B or are they cuttign more axle slot to pull the wheel up closer ? saying 1 1/4 inch seems a random statment, but i guess that picsa , comment is part of some kinda sequence ?
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Quote from the article:
"A fishtailing problem that we thought was caused by the combination of tire/power band, can be easily solved by extending the trailing arm one inch on a diagonal cut. Refer to the photo for details."
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this is the Freaky s/arm in the Vandy framed , Iain built , Firko and many site members input DT1 pre 70 Yamaha (http://i1134.photobucket.com/albums/m612/Iain_Cameron/DSC_0090-2.jpg)(http://i1134.photobucket.com/albums/m612/Iain_Cameron/DSC_0092-2.jpg)
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I like it, I have the engine, but know frame
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dave the frame is chopped and lowered by 45mm by Vandy . Iain
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Wrote a long winded story & sent it to [dunno where!!] so start again.
Not long after the first DT1 arrived at the shop [december "68] something turned up from USA on modifying the square arm which was add an inch & step it 'up' an inch [to rake the front out more] Think there idea was to give it more stability for desert racing. So i did this to mine & the boss's bike. Also we altered the forks [steel slider first model] as per instructions which meant welding up damper holes & drilling smaller ones. Recall that after that we had to run less oil [think 190mls as opposed to 2something] or couldn't get full travel--doesn't make much sense now but anyway. Also [wish i knew where it got to] was an air cleaner box to make [not by me], had a large 'still air area' between filter & carb & used a car type paper element [which was useless in dust but we didn't know any better--till the Filtron green filter came out]. Mod to arm was done at the axle plate, sort of a Z shape plate, [not a Z but straight down & 1 inch wide then contoured top & bottom so it looked right. These days i'd just go back an inch without stepping it up!!. Might start another DT1 story [thinking]. Cheers Morley.
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The mods you mentioned where in Dirt Bike in 73 the story ran over 6 issues . the z plate was used to get the s/arm in a parallel plane to the ground then they used Girling shocks . Iain
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"73's a bit late to be thinking of modifying the square arm, [broke mine more than once by then haha] did ours in probably 69/70,maybe "71, might be wrong, december "68 on ownership papers but damn it i scrapped the frame many years ago, so bike as it is--is a bit like an axe with a new head & new handle!! & numbers don't relate. Just sulking looking at your YZb photo, remember getting a couple of A model redundant stock bikes to sell where i worked, think sold for $800 or something after the B model then MX models came out. If only we could turn the clock back. Morley.