Carburetor Modification Part 4

One of the benefits of installing the smaller Scrambler tank is, since it is physically smaller and sits higher on the frame, I can now perform all the carburetor tuning without having to disconnect hoses or prop the tank up. Following the results from the last round of carb testing, I determined that the idle/slow jetting is slightly rich (fixed by adjusting the air screw), the midrange is too lean, and the top-end of the bike still surges and stumbles.

Much more room now with the small tank

 I solved the midrange problem by installing the next higher-size needle jet (P-6). For the top end, rather than change the jetting, I reinstalled the sheetmetal baffles in the float bowls and lowered the float height. Both of these steps will lean out the mixture (and make the carburetors stop leaking fuel!)

The shakedown ride I took following these changes was encouraging. It now idles perfectly and accelerates strongly right off the line. There is still some stumble at full throttle, but it can now cruise at 60-65mph with no hesitation. I'm sure the correct setting is within reach, but I'll have to wait for warmer weather to really open it up and test it. The current carburetor settings are:

Mikuni VM26-8074

Main Jet: 130
Pilot Jet: 35
Needle Jet: P-6
Needle: 5F21
Air Jet: 2.0
Slide: 2.0
Float Valve: 2.5
Air Jet Turns: 2
Needle Notch: Center
Float Height: Approx 17mm

Hard at work with a cup of hot tea

CL450 Racer - Installing the Original Tank

When I purchased the hulk that would form the basis of my 450cc land speed racer, it was incomplete and didn't come with a gas tank.

Among other things

I had a larger CB500T gas tank installed on its original motor-less chassis, so I swapped it onto the new frame and modified the mounting points to suit. That tank served me well, until I stumbled on an original CL450 "Scrambler" tank on Craigslist.

That seat came from a junkyard and is WAAAY worse than it looks.

The inside is surprisingly clean

I was browsing for a donor tank to put onto the rolling chassis I assembled in my previous post, but the opportunity was too good to pass up. I decided to refurbish the scrambler tank, put it on its correct chassis, and return the 500T tank to its original home.

CL450 with the 500T tank

Lean and mean with its original sheetmetal

The scrambler tank weighs 5 pounds less than the 500T tank, and holds around 1 gallon less of fuel, so now the bike handles brilliantly :-D . Next up is to refurbish that seat, so I can actually use this machine regularly on the road.

Machine Tool Spotlight - Star Lathe

Over the Thanksgiving holiday, we picked up a vintage lathe from a friend who had snagged it at an estate sale. This one is a true antique, and makes my '40's vintage Hardinge look modern by comparison! We also picked up a small Craftsman lathe, which will be featured in another post.

This is a Star Lathe, made in Seneca Falls NY circa 1900. The bed has several patent dates cast into it, the most recent in 1896.

Original paint is still there under the grime

It is equipped with auto feed in both axes, babbit bearings, a 3-step flat belt pulley, and an auto-oiler for the main bearing that appears to have been borrowed from a steam engine. This bad boy is Victorian Era state-of-the-art.

The oiler is particularly interesting. It is made of a glass cylinder sandwiched between two brass caps. A knob on the top adjusts the size of an air hole, which alters the gravity feed rate of the oil. This allows for continuous operation without having to constantly stop and check the lubrication.

When this lathe was first produced, electricity was still relatively new and rare. Because of that, it came in two versions. The first is this one, which could be run off of a common belt or motor. The second version is treadle-powered, similar to early sewing machines.

This machine is in incredible original condition. None of the parts are damaged or excessively worn, and the original paint is still present. Therefore, I think the "restoration" will only consist of a general cleaning and re-oiling of the moving parts. I may also check the various bearings and bushings for any debris or damage before repowering it with an electric motor. Although, perhaps I could dig up a pedal drive...

CB500T - The Resurrection

After reassembling the 450/500T frankenstein, I was left with alot of spare parts, and the remains of the 500T parts bike. I didn't have any takers on craigslist, so rather than scrap it all or have it clutter up my shop, I decided to reuse all the leftovers to build a new race chassis. I have no idea what I will use it for, or even what kind of fuel it will run on, but at least it puts alot of junk to good use!

The hulk

Stripping the front forks.

Pressing in new fork seals

1 down, 1 to go

Forks, new tire, and center stand

Rebuilt a spare wheel and installed. All that's left is a new tire, reinstall the fender, and I can put it in storage.

KZ400 Diesel - Rebuilding the Electrical System

The last major repair I wanted to make to my diesel bike, before putting it into winter storage, was rebuilding the wiring harness. I got the bike as a bare frame, so I had to make a harness from scratch. At the time, I had no experience building an electrical system, nor did I know what proper wiring practices were. I was a simple mechanical engineer, and all I knew was (shudder) electrical tape, zip ties, and hard plastic spade connectors.

Since I didn't originally intend to make the bike road legal, the first system was a crude total-loss setup to turn the headlight and taillight on. As the project progressed, I added new circuits and zip-tied them to the original wires. By the time I had finished the bike, I had added brake lights, a horn, and a charging circuit, and the harness looked like this:

Good luck tracing THAT out

Why on earth would I put the fuse THERE?!

Different angle, just as bad...

 Obviously, something needed to be done. I had used a mash up of different wire colors, none of which matched, and it was nearly impossible to find any shorts that occurred. To fix the problem, I bought 5 different wire spools, a box of Honda-style bullet connectors, a real crimping tool, and set to work.

This is a beautiful sight to me. That is why I'm a geek.

Much Better

There! Not bad for a mechie.

Carburetor Modification Part 3

Jetting a non-standard carburetor for an engine, especially when no one has tried the combination before, is an extremely time-consuming process of trial and error. I reasoned that the original jetting would be a close match, or at least a decent starting point, because the three carbs had previously been mounted to a Triumph Trident, with each feeding a 250cc cylinder. What I didn't take into account though, was the possibility that the previous owner may have jetted it TOTALLY WRONG.

This is becoming an annoyingly familiar sight...

 Mikuni carbs have three main fuel circuits: the pilot circuit for 0 to 1/4 throttle, the midrange circuit for 1/4 to 3/4 throttle, and the main circuit for 3/4 to full. After weeks of fiddling, testing, and tinkering, I have determined that the pilot circuit was JUST ABOUT right, the midrange was extremely lean, and the main was extremely rich. In fact, the disparity between midrange and main was so large, that it created the illusion that it was jetted correctly, but had an air leak/low range stumble. The rich main supplemented the lean midrange and they compensated for each other, while causing poor power and a tendency to stall at low throttle.

Needle Jet Swap

Seriously, I've had enough of propping the tank up...

I think I'm pretty close to getting it dialed in mostly right, and will post the final settings when I have them. Though, I think I should bring it in to a tuning shop and have them doublecheck it...and also rebuild the brakes....possibly replace the clutch plates...sooner or later it will be "done"!

Loring Timing Association 2013

This past July we made our annual pilgrimage to northern Maine for the Loring Timing Association's Maine Event. It is held on the former SAC runway at the decommissioned Loring Airforce Base; 12,000 feet of smooth, flat asphalt. It is so flat that, because of the curvature of the earth, you cannot see end-to-end!

This year, we set records with both the diesel bike and the CB450/500T Frankenstein. The diesel managed to just break 60mph, and the 500 was limited to 92.3mph due to nearly overheating from an intake air leak. I'm posting some of the pictures here, and the rest can be found at my friend's smugmug page:

http://dfalk.smugmug.com/Photography/2013-Loring-Timing-Association

RIP Bill Warner

The Perewitz's and their monster.

Somewhere in there is a BSA Scrambler

A sample of the madness

Barbecue!