Works Ohlins Yamaha YZ360 doesn't meet minimum friend requirement for Farleigh

I have been hesitant to put this build on this forum, because to be totally honest, I don't like most forum people, so we can just get that out of the way. The few of you out there who know what you're looking at, this ones for you. The few of you who maybe don't know what you're looking at, but are interested in learning more, this is for you, too. The majority of you who'd rather argue the ramifications of Ken Roczen not tagging his current underwear sponsor in his latest IG post probably won't find much here.

There will be a lot of text. Feel free, rather than complaining, to just look at the pictures. I got a degree that way, so you can look at dirtbikes that way without bitching, if you're not into reading. I'm not even reading this.

Just saving folks some time on the front side, I know how precious a commodity that is.

There won't be perfect chronology. The bike is 90% complete as of 8/26/20.

In the early 90s, I decided that the Ohlins 360 was the coolest thing I had ever seen and eventually I'd build one. Larry Brooks, Kyle Lewis, and Shawn Kalos holeshotting works 500s on Noleen 360s just resonated with me in '93. They seemed so much more nimble, and entered corners like a 250, but exited like a 500.

In 1988, Ohlins developed an open class kit to address Yamaha's lack of a water cooled Open bike. The idea, it would appear, was to use Yamaha parts, virtually all Yamaha parts, save for the cylinder and head itself, and a 360-specific exhaust. There were, or so I've heard but not verified, 999 of these made.

There are a lot of common misconceptions with this set up. The two big ones I hear a lot are:

"It's a big bore kit." - No, its really an entire engine package that uses 250 cases and transmission. Drop this cylinder, head, piston, and rod into a YZ250 and it wont make it across the yard in one piece.

"It uses anything from 88-98" - Ha, only if you have something against your boost port and enjoy blocking it. Otherwise its 88-91 cases.

I never owned a YZ250. I decided it would actually be better to build an entire bike from scratch. I wouldnt use much from a used bike. This bike is almost all NOS. Not sure if anyone reading this has done it, but its an exercise in insanity if you've done it with a YZ. The Hondas are like "Skill level 2" models..theyre dirtbikes, but they have 30 years of parts commonality. Everything fits everything else, it almost seems like. Almost. Yamaha builds 1 year "transition" bikes from new to old model. They've done it since the 70s. The 96-01 is 3 different bikes. Forums think radiator shrouds denote bike changes. Between the 125 and 250 there are about 6 different swingarm part numbers there alone.

The basis of the motor is:
-88-91 YZ250 cases (go ahead and run 92+)
-YZ250 crank counterweights
-YZ490/WR500 conrod, pin, bearing
-1979 YZ400 piston (a one year transition piston, 82mm)

The intrinsic drawbacks are:
-Adding a ton of weight to a rotating assembly, in the worst possible place requires lots of balancing and the addition of tungsten.
-Renders motor incredibly oversquare at 82mm bore x 68mm stroke, no bueno for MX twostrokes
-250cc crankcase volume very low for producing high RPM power with 360cc.
-Every secondary and tertiary engine/chassis component designed around 41hp engine

"If you don't balance that thing perfectly, its like standing on the brake at 8,000 rpms."

-Doug Dubach, US Factory YZ360 development rider 1989

Initial Thought Process on Set-up and parts combination:
- "Man, I really loved the 1997 YZM400, too bad it had that piece of shit lump that tried to kill the guy til they beat it into submission in mid 98."
- 96-97 Chassis for best parts commonality. 1998 is a one year bike/frame. With 96-97 I get two years on most things, save for some small items like the chain guide. (telling you, Yamaha is all over the map)
- Handmade swingarm +25mm length, 1991 works YZM design, for increased length & lateral rigidity to accommodate increased torque.
- Alloy tank
- Ohlins Suspension, front and rear
-Showa HPSD (Honda Progressive Steering damper) fixed to chassis.

Well, on with it.

So I found a 97 chassis, very lightly used, and began modifying it.
-I first, taught myself how to weld. Once i was satisfied with my own ability to stick two pieces of metal together on something im going to jump The Leap on. Get the giggles out now, it wont be funny for long.
-Then I removed the CDI hanger, the rear brake remote reservoir interfaces.
-I added 3 skid plate tabs for a 05 GYTR skid plate and water pump guard. Fabricated them simply by best guestimation on how thick i needed to make them to jusrt tap directly through, and strong enough to not bend under the weight of the bike on the stand. I then measured and welded the mso that the glide plate hangs ~5mm lower than the cradle, so the cradle doesnt sit on the stand anymore.
-I measured and fabricated the HPSD mount and welded it on. It's not pretty, but it blends in with the rest of the birdshit OEM Japanese welds and wont break. Plus, I didnt have to leave it at some asshole's metal fab shop for a week, so he could explain to me 400 reasons why this one weld is harder than building an offshore oil rig in a tropical storm and he has to charge me $100 for 11 minutes of labor...like 3/4 of them do.
-I also reinfoced the footpeg pin orfices. They're press-fit (with a firm hand) now. No vibration.

I achieved the color by:
1. Media blast with aluminum oxide so my frame isnt embedded with a bunch of silicate based shit.
2. 180 grit...220 grit......400 grit..... Scotchbrite... you know the drill.
3. Torched the existing welds to get a nice blueing, then saturated the hot metal in a lanolin based penetrant.
4. I am anti powercoat. if building bikes is art, powdercoat is crayons. But there isnt a clear on the market strong enough to withstand the beating of moto. so, i conceded this once. I pre-baked it to remove impurities (penetrant) and thats what gave it that bronzed overtone.
5. Sprayed it
6. Baked it
7. Chased and tapped everything twice. Dont like threading hardware into a sugar cookie.