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Here is one of the wb shocks.
I also roughed in the Boyesen ports a little more, blended the transfers and re-aimed the secondary transfers. Almost done with the hard part.
34mm Mik from an '82 and a YZ400D reed cage blended with a little epoxy should make a difference... I could have gone with a MT or Rad Valve, but I want to stay period correct. I will use Boyesen dual stage reeds. Anyone have a suggestion whether to keep the reed stops or eliminate them?
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Mossbarger is making reed blocks if you are going for period correct
I think the price is pretty reasonable too
That's pretty cool you are rocking a boost bottle
How are you connecting it? Back in the day we had no problem hacking right into the reed boot with a wad of silicone. 30 years later I'd still do it but I'd sure be a lot cleaner about it
I worry about the reeds opening too far and fraying from hitting the insides of the reed cavity. I guess I'll have to see what it looks like when it all goes together.
The holes not only allow the reeds to close faster, they allow them to open farther and faster than without the holes drilled. It eliminates the air pillow that gets trapped between the stops and the reeds, but also lets air between them so they don't get vacuumed open, sort of.... Hard to explain.
Anyway, I will get better pics and show some finishing work when I get the time. I'm also considering a 1/4" reed spacer so the reed block doesn't block the boost port.
I will turn a spigot from 6061-T6 and install it into the boot. Probably seal it with black silicone, maybe even turn threads and add a nut to secure it. I use an ice cube to smooth the silicone since water won't hurt the RTV. Works great.
A service bulletin I found on the 79 yz 125 says 15 kg cm 2 for pressure. This converts to about 213 psi. Does that sound right?
Do I fill all the way with oil like a new shock...or is there a specific amount?
Thanks
It has not had a remote reservoir added.
The 37 year old oil didn't look too good!
I've seen worse oil, but that's pretty ugly. Are you revalving the shock?
My other bikes are more of a priority to me and I only ride the yz a few times a year. I know I could wrap a bunch of money into the suspension but I think I'll just start with some fresh oil!
Pit Row
I wonder If so I could do similar with the '83 YZ100 cylinder.
But yeah, I did the same on a YZ80 cylinder and it made a difference even with small Boyesen ports. The size of the port is limited by the stud location and layout, plus you don't want to port until you see daylingt lol! There is such thing as too big.
These ports are an evolutionary thing. Invented in the late 70's by Eyvind Boyesen and used by Honda I believe first. It took Yamaha a while to catch on, or rent the patent (early-mid 80's). The ports help pipe effect and performance overall.
I myself would not use the press method......a race tech dealer ( who shall remain nameless at the moment ) pressed on my shock and broke the lower spring mount ....the dremel method is just as fast and much safer
that nasty 30 yr old oil coming out of the shock sure does SMELL
I wasn't going to change the port timing at all, but after cleaning up all the garbage in there, I figured I'd at least map it to see how bad they really are. Most of the ugliness is from the bad job I did in the rubbing and tracing, not the actual port clean up. Need to re-do for a more accurate map. One step forward, two steps back!
Does anyone know what the rod length is on this bike?
Got the Cylinder all set, 34mm Mikuni, 6-petal YZ400D reed cage and a modified '74 Penton ISDT125 radial head, and added the RF boost bottle.
Gained a bit in the mid, but top end just shreds. Never had a 125 wheelie up a sand hill in 3rd! New head kept everything nice and cool. #300 main.
Had the head welded up by Leominster Micro Welding, so I could relocate the plug and stud holes. They're the best welders I've ever worked with. Amazing.
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