Scraps - Building a Seat

I wasn't able to find a complete Yamaha YG1-T seat for use on Scraps, so I decided to build a new seat pan and mounts for a seat that could accept a new vinyl cover for the Yamaha seat.  I ended up finding a bunch of scrap metal in the "free" bin at the local steel yard, so I set about cutting, grinding, drilling, and welding.

Then I made a few brackets for mounting the fuel tank, seat, and a luggage rack off a C100.  Nothing is pretty at this point, just raw steel in the correct shape.  I'll need to spend some time rounding off corners and making things much cleaner looking.  the front bracket mounts the rear of the tank, and the front of the seat pan. Like the Yamaha seat, I used slotted brackets up front that slide over a horizontal bar.  Then the rear of the seat bolts to a bracket.

And then this morning, I started fabbing up the exhaust.  I wanted a mid-pipe, and I was able to use a bunch of different curved pipe scraps to build the thing from cylinder head back to where I plan on mounting a simple muffler.  It hugs the frame pretty tight, and I gave it a gentle turn around the rear shock.  The whole thing will likely get wrapped and have a small heat shield in the general leg area.

New seat pan, made from scrap sheet metal

Front bracket mounts tank, and front edge of seat

Start of exhaust build.  Simple mid-pipe

El Guapo - More Exhaust Fabrication

I spent the morning out in the garage working on the exhaust. I made great progress, in fact I finished it up, save for some final cleaning up and a wrapping.

Roughly 8 cut and bends in total make up the full exhaust:

The rear portion of exhaust bends inward, to clear the shock. This keeps everything nice and tidy:

Rear mount it tucked up under the seat:

El Guapo - Exhaust Fabrication

I wandered out to the garage this evening, pomegranate mead in hand, and decided to start fabbing up the exhaust on El Guapo. I literally had zero stock exhaust parts for any of these S90/CL90 bikes this is based on, so I have to fab everything up from the header flange on back.

I'm doing a high pipe, like any good scrambler should have. So far I've used a piece of precurved pipe from an old mop bucket handle that broke at work, to a scrap header pipe from a CB160 that was damaged, to a large washer that was drilled and cut down to act as the flange.

It is a little hard to see in my fuzzy cell phone pic, but the header and uppipe are in place. Those are the most difficult items, since they have the tightest radius bends. I need to grab some 1" thin-walled conduit for the rear portion of the exhaust, which will make a bend in and around the rear shock, to keep things nice and tight to the body. I'll likely use a muffler that came on a cheap ebay XR50 exhaust I bought to use for parts on the Trials bike.

As you can see from the mess, it takes a lots of parts and tools for this portion of the fab work.

Miyata Details - Exhaust

This is one of the parts on the Miyata that is quit a bit different than any of the other bikes I have. The header pipe is conventional, but the main exhaust expansion chamber has a mount built into it, and a silencer. The rear part of the expansion chamber actually fits over the end, and is secured with a nut that attaches to the long threaded rod sticking through the middle.

Main diameter is 1", then expands to 2.75".

Kawasaki Exhaust Part Deuce

I decided to hack apart the stock exhaust and fashion myself a new one. I used the front half of the stocker, and built a new rear section using the calcs I put together for a proper expansion chamber size/shape. It went rather smoothly.

I even fashioned a little aluminum heat shield, and wrapped everything up in the leftover exhaust wrap from the BS-7 project.

As mounted:

Kawasaki Exhaust

I cleaned up the stock exhaust and mounted it up last night. It isn't my favorite look, as it seems to be about 6-8" too long. It has the expansion chamber shape built into it, then a muffler chamber at the back that also contained a spark arrestor. It isn't terrible, just not my favorite.

It does tuck up nicely to the frame, and even has a notch to clear the rear shock. So My leg has tons of clearance when sitting on the bike.

If I get lazy enough this weekend, I may sketch up a different design, with a fatty expansion chamber shape.

Bridgestone BS-7: Exhaust Finished

I got out this morning, before it got hot, and worked on the exhaust. I wrapped it with exhaust wrap, then built a little aluminum heat shield. Nothing too exciting, but i fun to shape the heat shield out of some scrap aluminum sheet.

I also fit a new carburetor Thursday evening, as the original was acting goofy after I cleaned it out. I had a spare 20mm Keihin carb, but it is a bit bigger in overall outside dimensions compared to the stock 15mm that came on the bike. I built a new intake manifold that was just a tick shorter, and angled up about 5-degrees. This allowed the carb body to clear the frame on top, and the engine case on bottom.

I'll likely see if I can kick it over tomorrow morning.

C'

Bridgestone BS-7: Exhaust Options

A couple options for the exhaust on the BS-7.

The stock setup, with the original chrome downpipe and muffler. It weighs 9 pounds, plus a pound for the rather robust mounting bracket, and is very much built for low-end performance. It also makes it harder to package the rear brake lever and footpeg.

Something I cobbled together over the weekend. It uses an old S90 muffler as the basis, cut into pieces and welded back up into the desired shape. It is built to give peak power a bit higher up (6,000rpm) in the range. It comes in at 4 pounds, and mounts to an existing hole in the frame. I plan on wrapping it in exhaust wrap, and building a small heat shield to keep my right leg from getting burned.

I prefer the high pipe, as it will make more power, and gives more clearance.

Bridgestone Updates: New Exhaust

I have a few updates and upgrades to make on the Bridgestone. Including revising several items I've fabbed up recently. Such is life.

What I've realized is that my footpegs are too high, so I'm not comfortable on the bike. Way too much weight up on my wrists, and my legs are too cramped. Also, I had no real good way to attach a rear brake light switch to the brake lever I built. Normally I build a brake lever that mounts behind the swingarm, with the toe peg poking out below the swingarm and above the exhaust. Unfortunately, there was no room with the stock exhaust. So step #1 was to build a new exhaust.

The result is shown below. I used the spare header pipe and an expansion chamber I had in the parts bin from a YSR50. Since the YSR50 is a very peaky 50cc engine, this expansion chamber actually closely matches the dimensions Bridgestone shows for building a hot rod exhaust for the 90cc engine with a lower rpm peak.

Exhaust mounted up, just shot with some high temp black paint for now:


Tons of room for relocating the footpegs and brake lever downward a few inches:


I'll likely wrap the exhaust once I finish fabbing up the rest of my mods.

C'