Author Topic: Straight cut gears DT1, where?  (Read 395 times)

0 Members and 1 Guest are viewing this topic.

Offline John Orchard

  • Legend
  • *****
  • Posts: 2793
  • ^^^ Jan 1984
    • View Profile
Straight cut gears DT1, where?
« on: January 25, 2019, 04:51:50 PM »
If I wanted to replace the primary drive gears on a DT1 with straight-cut, where would I start looking, anyone know?
Johnny O - Tahition_Red factory rider.

Offline OverTheHill

  • Legend
  • *****
  • Posts: 788
    • View Profile
Re: Straight cut gears DT1, where?
« Reply #1 on: January 26, 2019, 07:21:00 PM »
  YZ250A & B. Had some on mine from some leftover A bits i was given many years ago. So far as where to look, they'd be as scarce as Hens Teeth. That's assuming, come to think, that your talking clutch & crank gears which i dare say you are. Cheers.

Offline OverTheHill

  • Legend
  • *****
  • Posts: 788
    • View Profile
Re: Straight cut gears DT1, where?
« Reply #2 on: January 26, 2019, 07:54:54 PM »
Just incase you're not aware, the gear change on the A & B has a shorter throw. I'll put a link to the two parts which are pretty obvious anyway. I 'did' have those bits but buggered if i can find them now. I never used them as i liked the amount of movement of the original DT1. My theory probably was--seeing i never use the clutch, the dogs need as much help as they can get to [Get in There] so less lever travel means less leverage. Stupid theory i know. Probably just thinking back to my Triumph Metisse that had a very long movement.
No8 in first link & No24 in the second. Reason being they changed the position of 31 so it is closer to the pivot point, if that makes sense.
https://www.partzilla.com/catalog/yamaha/motorcycle/1974/yz250a/shifter-2
https://www.partzilla.com/catalog/yamaha/motorcycle/1974/yz250a/shifter-1
link below to the clutch & crank gears while i'm at it. Intersting thing is i see they've drawn the crank gear helical like a DT! which is wrong but can see in the cluch link they've drawn it straight cut. Both 431 if that means A or B so must be right. Hope i'm not confusing everyone woffling on.
https://www.partzilla.com/catalog/yamaha/motorcycle/1974/yz250a/clutch
https://www.partzilla.com/catalog/yamaha/motorcycle/1974/yz250a/crank-piston

Offline OverTheHill

  • Legend
  • *****
  • Posts: 788
    • View Profile
Re: Straight cut gears DT1, where?
« Reply #3 on: January 26, 2019, 08:17:06 PM »
But wait there's more lol. The crank wheels are Tricker. Not sure if they're lighter but should be as are sort of hollowed out where you can't see. Thought i'd lost mine but found them recently in my short stroke 360 [325] when changing it back to the full 360 crank. Just realised i still have a rough set in my trademe listings so here's a ink if you want to look. Not sure if its these wheels or my other set but by memory i slid either the lead weight out or the alloy tube bit [think that bit] & was hollowed out behind it. So thinking the outer rim might be or must be a separate item fitted on after. Seems like a hell of a lot of trouble to go to to save weight & no doubt all added to the cost. also if i remember right the crank pin is a mm or two bigger than a DT1. They used a 360 pin & a roller cage with small rollers. well essentially just a 360 roller assembly & crank pin. as same rod ID as the 250. Sorry getting off track & lost. You'd better double check my info but nothing wrong with my long term memory--i think. Forgotten the question now.

Offline John Orchard

  • Legend
  • *****
  • Posts: 2793
  • ^^^ Jan 1984
    • View Profile
Re: Straight cut gears DT1, where?
« Reply #4 on: January 26, 2019, 09:54:20 PM »
Thanks heaps, all great info !

l wonder if l could modify/cut/weld to make my own short-throw shift linkage? l look at that next week.

What is the "trade me" link?
« Last Edit: January 26, 2019, 09:56:23 PM by John Orchard »
Johnny O - Tahition_Red factory rider.

Offline OverTheHill

  • Legend
  • *****
  • Posts: 788
    • View Profile
Re: Straight cut gears DT1, where?
« Reply #5 on: January 27, 2019, 08:07:23 AM »
Brain fade lol. I'm in NZ. Link here to TradeMe which is our version of Ebay. Might have to copy & paste this link if not live.

https://www.trademe.co.nz/Browse/Listing.aspx?id=1920464638

Catch ya later. Off to spectate at our annual Woodville MX which is probably our countries biggest event with riders from all around the world some years. Here's a sample. Been going 58 years & think i rode from "63 if that adds up lol. Became an international from "63 with british, swiss, german riders. Great days those. Alky burning BSA 500, missed a gear & bent the valves. Head off in 5 minutes & front axle out then punched the valves straight & carried on for the day no problem haha. Cheers Morley Shirriffs. ps, i see your message, worry about it tonight.

https://www.youtube.com/watch?v=HjwykJcNVi4 8)