[Tanshanomi]

Continuing to plug away at the seat, trying to make a little progress whenever I get the chance.
It looks a bit amateurish, but I'm not too ashamed of it. After all, I'm an amateur.

 

[woodsman]

It turned out well for the first effort and new tools. You need to be looking for faults to find them, nothing jumps out. You are more critical because you know where to look.

 

[Tanshanomi]

Finished upholstering the seat. My stitch lines are a bit haphazard and the fit is slightly wonky in spots, but I'm not too disappointed. It'll be a perfectly serviceable part, and not horrible looking for my first shot at doing this sort of thing. Now on to fabricating brackets to bolt it to the frame.

 

[Tanshanomi]

I was about to bend stock into brackets to hold the seat, when a light bulb went on. I would basically be recreating single-hole conduit clamps, so why not just buy some of those?

Meanwhile in other news, I started work on my revised steering clamps. I'd previously bought a GS500 triple clamp for one of my other projects [The Aermacchi-Ducati Special]. With just a tiny bit of mathing, I discovered that the GS steering stem is the proper length to fit the Bultaco frame without the kludgy spacer I'm currently using, and without turning down the steering stem. Unfortunately, the GS500 has larger fork tubes and the wrong clamp offset, so the triple clamps are not suitable. Therefore, I bought two additional steering stem/lower clamp assemblies: one GS500, one from a GS650L (what Bultakenstein uses). I ground away the welds on the bottom of the stem on each and pressed them out.

As i suspected, they have identical diameters at the bottom. After a quick swippity-swappo, a quick trip to my friendly neighborhood welder is all that's needed to have a GS650L lower steering clamp wedded to the shorter GS500 stem.

Perfect! Oh, no...wait. The GS650L top clamp doesn't bolt to the other end GS500 stem. I ended up cutting apart a spare adjustment nut to make a threaded collar, and then turned a stepped alloy spacer to make a cap nut.

The whole stack goes together like this, and another sticky issue resolved.

Bultakenstein's existing steering stem won't go to waste. It will get used on yet another project I've come up with, mostly to use up a lot of Bultakenstein's rejected parts.

 

[Tanshanomi]

I mounted the seat this morning. Nothing very high tech, but still a minor milestone.
I hit the conduit clamps with some dark gray paint to make them less noticeable, then I glued strips of 3mm neoprene inside them to give them a snug fit and protect the frame once it gets painted.

I initially tried attaching the clamps to the plastic seat base with self-tapping screws, but that was clearly the wrong way to go. So, I disassembled the seat shell from the base and installed rivnuts into the seat base from above. Even though they're intended for metal plate, they expanded out into the HDPE base material nicely. I could then use 6mm bolts to snug everything up from underneath.

The weight of the seat sits on four plastic furniture feet to protect both the frame and the seat cover snaps.

 

[Tanshanomi]

The revised steering stem setup is coming along nicely. The GS500E steering stem is a snug slip fit into the GS650L lower triple clamp. I mocked everything up, and I just needed to make a couple of tweaks to get it set up.

The bearing-to-bearing distance in the frame is just slightly short for the stem (just a few millimeters). So, I chucked up the stem in the lathe and extended the diameter where the upper bearing fits further down the shaft a bit, to ensure the bearing has room to float once everything was properly adjusted. I also had to undercut the area at the end of the threads, so the nut won't bottom out, and can travel past the end of the threads slightly if needed. (No criticism of the turned surface, please. I bought some new carbide tool tips off Amazon and they are utter crap.)

I was more liberal with the increased travel than I needed to be—about half the thickness of the bearing—but there's really no functional downside to that. One reason I did this was that I mocked up the fit using a plastic analog in place of the bottom bearing. I didn't want to press the bearing on yet, since the stem has to be welded up first, and I also need to make a steering stop adapter that will have to go on the shaft first. I made this HDPE as close as I could to the correct dimensions, but inaccuracies creep in when you do things like this. It would be a total bummer to get the whole thing welded up (at which point I won't be able to fit the stem in my 8" lathe), and then discover at that point I didn't take enough off.

Next step is to re-weld the stem to the lower clamp. I will be dropping the assembled forks by my local welder this afternoon, and he should have the job done within the week.

 

[woodsman]

Once in place your machine work will likely never be seen again.

 

[Tanshanomi]

I got the front end back from my local welder, all nicely TIG'd up. I now need to rework the steering stops before the front end can go back together.

 

[Tanshanomi]

Bultakenstein has taken a back seat to a couple of other bike projects the last couple of weeks, but this morning I started working on a new steering stop adapter for the revised steering stem setup.

As always, watch this space. More to come.

 

[Tanshanomi]

Steering stops complete, and front end reinstalled with new stem and bearings. The result is no aesthetic beauty, but it's a pragmatic and functional solution to a specific issue. The important thing is that the integrity of the steering stem is no longer questionable.

 

[CaTacL1sm]

that looks great.

 

[Tanshanomi]

I rolled Bultakenstein outside for some progress shots, to keep me motivated. Chassis fabrication is basically complete; now it's on to engine work, intake, and exhaust. There have been a lot of changes, re-work, and second guessing my choices along the way, but I can honestly say I'm pleased with what it is at this point.

 

[CaTacL1sm]

This is turning out fantastic.
Easily the longest running project in CR.net history lol

 

[Tanshanomi]

Trying the speedo from a Suzuki GZ250. It's a bit on the large side, but the angle and placement are nice. i think I like it!

 

[woodsman]

It's a nice looking instrument and panel. The neutral and signal indicators are clever.

 

[DrGonzo21]

Diggin 'it.

 

[Tanshanomi]

THE BRIDE OF BULTAKENSTEIN
If you're wondering why progress on my Bultaco has slowed lately, here's the explanation.

I looked around at all of the cast-off parts cluttering my workshop, (most of which were originally bought for this project but got rejected for one reason or another) and got a crazy impulse to do something with them. The Can-Am Qualifier tank, original GS650GL forks, my old set of triple clamps with the machined steering stem, and YZ125C swingarm that were all part of this thread at one point or another are now getting hung on a 1974 SST Panther Black Shadow 175 frame I bought for under $100. The seat was similarly rejected from my CL125S project.

About this time, my podcast co-host Garrett re-powered an old KX125 chassis with a Harbor Freight Predator engine. That got me more interested in industrial motor+CVT bikes. For $99, I scored a new 6.5 HP LCT StormForce 208 (Predator/GX clone) engine originally configured for snowblowers. I swapped the plug-in starting motor to a regular 12V starter.

Unlike Bultakenstein, I'm using new parts where my budget allows. The CVT transmission is a generic TAV2 torque converter off Amazon. The rear brake rotor, handlebar, and master cylinders are all new as well. It's going to have scooter/bicycle style brakes, with the rear brake on the left handlebar and no foot controls. Why? Because I can, so why not? The tires are Heidenau K66.

It's going together without a lot of drama so far. Not only do I have much greater skill and increased shop capabilities as I did ten years ago when I started the Bultaco, but it's also amazing how much easier it is to build a bike when you really don't concern yourself with aesthetics.

Not sure what purpose it will serve, but it's an interesting diversion.

 

[Tanshanomi]

Quite possibly the stupidest motorcycle ever built? 34" seat height and 3" of rear suspension travel. It's like some sort of daddy long-legs. Oh well, it's easier to move it around bolted together into something that rolls than taking up room on my shelves.

 

[CaTacL1sm]

so.... you should turn that into a baby bosozoku bike.

 

[Tanshanomi]

so.... you should turn that into a baby bosozoku bike.