'81 Yamaha XJ750 Seca w/ monolver rear and Hossack front

Working on suspension / brake force load tests and steering link design.

~1,400 lbs of brake force (2g brake)

Bump showing 5.5 inches trave (waiting on scale for force gauged test)

Steering link model (aproximate)
Steering links are done.


So, I took it for ride, soap box derby style.

Cable actuated master cylinder (a stock part) mounted to the fork so I can run hard lines. Will be using inverted levers to pull the cables. The BMX bars also stay, but will be modified a bit (for ergo and cable exits) - reach as shown in photo is great, but the wrist angle is all wrong.

I have no idea whether this thing is going to be beyond awesome or spontaneously combust but I love the fact that you just keep going with it.
Ended up being a bit of both. I got it running in 9/2017 and it rode quite nice, though the shock was a bit soft. But I blew up the engine when an oil line melted (they run very close to the pipes down near the oil filter). I got new engine is in for $500, and I upgraded the shock to a Huyabuse unit (850 lbs / in vs 650) and was quite happy with it, but only got to do a few short rides before the snow hit. I'm currently adding crash bars and ice studs to go ice riding at Mama Tried!

The first (and only) long ride... so far.

Replaced engine. Replaced front shock with Hybausa unit (850 lbs/in vs 650 lbs/in). Rides much better.

Built crash bars. Still plan a few things. A custom front shock linkage will improve the wheel rate curve to make it slightly progressive, and give me a bit of extra travel.
Bike is back on the road this spring as a daily rider. As designed for, its a fun traffic carver even with lane splitting being illegal - the reduced brake dive makes constant brake / throttle cycling less obnoxious, and it flicks through lane changes at a thought and goes over potholes at a 45 degree lean quite happily. Could use a bit more power and/or better aerodynamics; it does OK off the line but roll on past 60 is disappointing.

I'm planning a ~800 mile trip for this weekend, mostly on boring roads though.

Yeah, I've always been a fan and while I was doing the early build I found out about some local Mad Max themed rides and a big Mad Max themed camping festival in CA. Given my fairly crude fabrication skills, I figured I'd just run with it as an aesthetic.


I got to play on the track with some other Mad Max fans at the Flat Out Friday races in Milwaukee the weekend of the Mama Tried show.

I thought you had given up here. Happy to see an update though. The bike looks as shitty as ever. I mean that in the best way possible.
Sounds shitty too. Gives me a special warm glow the way it upsets the local HD riders. I think I'll go over the dealership for some test rides....
Do I like a bit of good engineering? Yup. Do I like a bit of tastefully applied (sloshed on) flat-black? Heck yeah.

The Hossack front end ticks all the right boxes for me, ever since seeing Robs absolutely mental GSX... (you know which one I mean!)
der_nanno said:
The Hossack front end ticks all the right boxes for me, ever since seeing Robs absolutely mental GSX... (you know which one I mean!)

I actually don't... am not really a regular here, and have a memory like a steel sieve to begin with. You have piqued my interest - link?

spotty said:
you don't mind if i pop in and watch progress do you ?

Course not, but its largely done... at least for this summer. All I currently have planed is mounting a regular (4") headlight opposite the LED and my gauges up on the BMX crossbar. Oh, and a tweak to the front shock link to fix my wheel rate curve.

My detailed build thread is over at customfighters.com and stretches back 5 1/2 years - http://www.customfighters.com/forums/showthread.php?t=61895

Amazingly, I'm still running the same battery as shown in that first post!
Figured I'd pop in with a couple of quick update pics. I put about 4,000 miles on the bike this year and am pretty happy with it. Soon I'll be taking it back into the shop this winter to do a few small upgrades / repairs (I tore up the back fender mounts really bad) and a deep cleaning. Also, my kid asked if I could build a SIDECAR, so if money and time allows, I'll at least be making a start on that! I want do do a full articulated / leaning rig, a bit like the Flexit setup, both for handling reasons and to keep with the mechanical madness.

This pic is from doing intermission entertainment for Flat out Friday in Milwaukee, same weekend as the Mama Tried show.


This one from out at Wasteland Weekend, a Mad Max festival near Edwards Airforce Base.

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