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Added reply in a thread YZ125 1979 Race build 10/30/2014 7:18 AM

Most of my time is being spent on the spare cylinder. Bringing it up to 1979 National specs as developed by Moto-X-Fox. I'm using that as a beginning guideline, but doing a little of my own updates. The head is a side project that I've just begun on.

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Added reply in a thread YZ125 1979 Race build 10/29/2014 9:00 AM

The shock on the '79 125 is the same as the 250 and 400, but with the addition of a 1/2" spacer between the piston and seal head which limits wheel travel to about 9". So, when I rebuilt the shock I just eliminated that spacer and gained back the lost ... more »

Added reply in a thread YZ125 1979 Race build 10/28/2014 9:45 AM

The only pics I have are what's above in this thread. I just disassembled it, inspected and cleaned it. Installed RT valving and used RT seal head. I cleaned up the reservoir inside and out. Then assembled. I'm running 175psi of nitrogen. I also used ... more »

Added reply in a thread Guy Cooper's Factory 91 RM250 sx bike resto 10/23/2014 7:20 AM

Did somebody say cavitation? Oh yeah, it was me! At least I'm right once in a while...

Added reply in a thread Guy Cooper's Factory 91 RM250 sx bike resto 10/22/2014 8:58 AM

LMAO, I'm so old school I was thinking piston not bladder! Yeah, that makes sense... I love how these works bikes are full of mysteries and conspiracy theories.

Added reply in a thread Guy Cooper's Factory 91 RM250 sx bike resto 10/22/2014 6:15 AM

Interesting about the shock. Is it a one-off casting? There was probably some casting flash getting in the way and causing cavitation or something.... What does the shim stack look like? It's coming along nicely, Nate! Looks precariously perched on that ... more »

Added reply in a thread tool for measuring bore: what's it called? 10/10/2014 10:56 AM

66.4mm (Stock) , 67mm, 67.5mm, 68.5mm and 72mm. Not a bad spread of choices compared to the newer machines.

Added reply in a thread tool for measuring bore: what's it called? 10/10/2014 10:14 AM

You made me look... since we're miles off topic anyway... Wiseco offers a standard bore piston at 66.4mm and two oversizes: 68.5mm (265cc) and 72mm (293cc) for a 2007 KX250. What year is your KX?

Added reply in a thread tool for measuring bore: what's it called? 10/10/2014 8:46 AM

Yep, I thought I said that. Wait, I did say that lol! Sometimes my thoughts don't come out as well in typing.

Chromed cylinders and ported iron cylinders can be effected because the port really is at an angle to the Cyl wall.

Added reply in a thread tool for measuring bore: what's it called? 10/10/2014 7:46 AM

If the Exh port roof is at a 45* angle (very steep, but for instance), then the change in port timing will be equal to 1/2 the bore change. A shallower port angle = less of a change. In your case, a bore change of 1mm = .0394". Divide by 2 and the difference

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Added reply in a thread Anyone have a source for DOW 9 coating? 10/10/2014 7:14 AM

Here's a good guide for the different types of Magnesium treatments: http://techplate.com/magnesium_processes.htm It's interesting to note that the Dow9 (type IV) is dark brown to black in color. All the coatings or processes provide no better than "Fair" corrosion resistance. But all ... more »

Added reply in a thread tool for measuring bore: what's it called? 10/9/2014 6:49 AM

That depends on the port angle. Just stating the obvious here... The more modern style transfers have a flat roof, so there shouldn't be a problem there. The exhaust port is the one I'd keep an eye on. Good call. I would definitely mention it to the ... more »

Added reply in a thread WTB 1990-1991 mugen me125 kit 10/8/2014 12:58 PM

The back of that cylinder looks like an XR100 head haha. Maybe that's Mugen's trick?!!!

Added reply in a thread tool for measuring bore: what's it called? 10/8/2014 12:55 PM

I don't use expensive tools. I think my 2-3" mics are SPI brand. The trick is how you use them: All my mics came with their own gauge. For example, my 1-2" mics have a 1.000" gauge that I can use to verify nobody has used them as C-Clamps when I wasn't ... more »

Added reply in a thread Guy Cooper's Factory 91 RM250 sx bike resto 10/7/2014 9:38 AM

Wow, nice work Hubb! I thought the only yellow bike you'd own is that MR50 or maybe a Fox XR75!

I hope you ran some Ar / Co2 mix inside the pipe while tracing the welds...

Added reply in a thread YZ125 1979 Race build 10/6/2014 9:21 AM

I didn't go directly through Race Tech though because I wanted a little vintage know how and help setting up my LUFT reservoir. I contacted Thor and we figured some stuff out before ordering RT parts. He was a big help. This picture is all I really had

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Added reply in a thread YZ125 1979 Race build 10/2/2014 6:11 AM

Hey Ken, The bike came out great. I'm very happy with the handling and suspension. The YZ250 forks with RT emulators gave some more travel and are perfect for MX. The rebuilt RT shock with the old school Luft reservoir works great as well. The motor

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Added reply in a thread 2014/15 Throwback Gear? 6/3/2014 10:12 AM

I switched from the REIGNMX shirt to the Oneal one for the second moto. The one with the skull on it. It breathes very nicely! And I don't mind the skull at all.

Added reply in a thread 2014/15 Throwback Gear? 6/3/2014 9:32 AM

ReignMX makes a nice shirt! I'm running the JT helmet too. Found it for about 1/2 price on ebay. It's the most comfortable helmet I've owned in many years! I got the JT chest protector from a friend on Marks MX site. Answer boots and THOR pants that

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Added reply in a thread 1977 Moto Villa MX 380 11/25/2013 9:24 AM

Very nice work! I like that you ride it instead of making it a museum piece. The Countershaft is a mile away from the Swingarm pivot. How is the chain? Sloppy?