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Author Topic: Pre-65 YDS VMX project.  (Read 8316 times)

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Offline Nathan S

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Re: Pre-65 YDS VMX project.
« Reply #15 on: June 30, 2009, 11:20:00 pm »
 :D We've already had that discussion...

Lozza: "You could....[long list of things], and then it would really howl".
Me: "I'm lazy and I'm a tight-arse. How about we just tweak the porting and get the pipes and ignition right?"
Lozza: *grumble, grizzle* "OK".

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Offline Lozza

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Re: Pre-65 YDS VMX project.
« Reply #16 on: June 30, 2009, 11:32:05 pm »
Hardly a challenge firko, just lots of dull grinding and lots of swarf ;D.The end result keeps you going a bit like painting the house. I wonder what's inside that centre lab seal thingy? The worst case is you remake the clutch side splined shaft, EDM a hole in the RD RH crank web and press the new splined shaft into the RD web.Done.
The only bad news is a can't find a 20 X 26 X 105 rod to replace those things.Only one that has the big/small ends correct is 117mm long. If your piston supplier has rods grab them.
I'll take that RD crank and any air cooled centres in the box. ;D
Me grumble and grizzle? When.......................................................... :D
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mx250

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Re: Pre-65 YDS VMX project.
« Reply #17 on: July 01, 2009, 06:01:04 am »
This is looking all very interesting. If you are gonna press things apart the 270 crank sounds an interesting potential. And if the ignition side is the same as an RD modern ignitions shouldn't be too hard to find and fit.

The RD had a 54mm stroke; what's the YM?

Fitting larger carbs (period of course) to the spigot mounts and/or mods to the mounts I see as another interesting challenge. 
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mx250

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Re: Pre-65 YDS VMX project.
« Reply #18 on: July 01, 2009, 06:16:30 am »
I'll answer my own question; RD and YM are 54mm stroke, whats the YM rod length? how close is the RD rod to the YM rod?
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Offline Lozza

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Re: Pre-65 YDS VMX project.
« Reply #19 on: July 01, 2009, 07:09:02 am »
I think Nathan said they are 105mm the RD/RZ has 110mm, RD 400 has 115mm the RD's have a 22mm crank pin YM a 20mm Crank has 13 splines like a TZ.
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Offline vandy010

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Re: Pre-65 YDS VMX project.
« Reply #20 on: July 01, 2009, 09:37:23 am »
yammie 125s have a 105mm rod length. not too sure about the hole diameters though.
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firko

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Re: Pre-65 YDS VMX project.
« Reply #21 on: July 01, 2009, 10:07:59 am »
Maybe I've missed the obvious but what's wrong with the original rods? What do the road race chappys use in their early TDs?
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Offline Nathan S

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Re: Pre-65 YDS VMX project.
« Reply #22 on: July 01, 2009, 10:15:35 am »
They're rooted.

I have not yet found any replacements - at least not any described/advertised as being for this motor.
As Lozza says, the 20mm big end pin is unusual in the world of Yamaha.

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firko

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Re: Pre-65 YDS VMX project.
« Reply #23 on: July 01, 2009, 10:29:46 am »
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mx250

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Re: Pre-65 YDS VMX project.
« Reply #24 on: July 01, 2009, 07:36:49 pm »
Quote from: Nathan S on July 01, 2009, 10:15:35 am
They're rooted.

I have not yet found any replacements - at least not any described/advertised as being for this motor.
As Lozza says, the 20mm big end pin is unusual in the world of Yamaha.


Have you asked the guys at the Yahoo group?
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Offline paul

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Re: Pre-65 YDS VMX project.
« Reply #25 on: July 01, 2009, 08:59:09 pm »
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mx250

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Re: Pre-65 YDS VMX project.
« Reply #26 on: July 01, 2009, 11:18:22 pm »
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Offline mboddy

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Re: Pre-65 YDS VMX project.
« Reply #27 on: July 02, 2009, 08:12:42 am »
Quote from: Nathan S on July 01, 2009, 10:15:35 am
the 20mm big end pin is unusual in the world of Yamaha.
Why not bore it out to take the 22mm crankpin.
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Offline Lozza

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Re: Pre-65 YDS VMX project.
« Reply #28 on: July 02, 2009, 08:31:32 am »
To do that properly you have to EDM the crank pin bore,not simply bore it out. That would be up to Nathan's discretion.
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firko

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Re: Pre-65 YDS VMX project.
« Reply #29 on: July 02, 2009, 09:58:42 am »
What about a stepped crankpin?
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