Part XI: Blue Smoke!

Mechanical Meditations

Saturday morning I sprang out of bed and was at the workbench by 8:00 am. The frame was back from the Doctor's and the only thing keeping me from starting the MB5 for the first time was assembling the thing! I forwent my normal morning mountain bike excursion and dove headlong into building up the MB. Progress was rapid; I had just about everything bolted up in a little over two hours. The final (I hope) parts orders arrived earlier in the week, so I had all the bits for final assembly. This close to completion it was great to find everything in just two locations. Bikemaster had most of what I needed: Clubman-style drop bars ($24.95), a replacement battery ($16.95), a #420 chain (cut to length for only $11.95) and two sets of mini turn signals to replace the MB's massive OE units ($29.90 for two sets). Motion Pro came through with one of their throttle assemblies and made up a custom cable to connect it to the Mikuni carburetor. The stock throttle cable has a splitter to run the oil injector pump, but I'll be mixing my own gas/oil so I pulled the pump and plugged the hole in the case.

[My neighbor Mike swings by every time I'm working on the MB, and this time he arrived just in time to lend a handlifting the engine into the frame. With the wheels on, engine in, bars installed and seat on it finally looks like a motorcycle! I hooked up the fuel line to the carb, poured in some gas, flipped the petcock on, and kicked her over. Halfway through the third kick she lit off with a pop and a big cough of blue smoke. After stumbling for a few seconds the bike settled into a reasonably smooth idle. The MB5 lives!!!

There are as many engine break-in procedures out there as there are engine builders, and after surveying a few mechanics and reading the recommendations at mopedarmy.com I chose to put the engine through three stationary heat cycles and two low-load heat cycles before calling it ready to flog. The Mikuni came jetted lean so I just opted to remove the main jet and run the needle in the richest position for the initial running – I'd rather soak my spark plug than seize my expensive Italian big bore kit. During its maiden voyage around the block the MB's crackling exhaust note garnered quite a few looks, most of them accompanied by an amused smile. Even with the stock pipe the MB puts out quite a bit of noise, which after 6 months of tinkering is literally music to my ears.

[With the carb set up as it is the bike will idle but runs so rich above 1/3 throttle that it immediately drowns.I know for certain the 97.5 main that came in the carburetor is dangerously lean (the stock 16mm carb runs a 105), so as difficult as it is to do, I’ll have to park the MB5 until I can pick up an assortment of jets. Hopefully I'll have some video for the next post!

Resources:

Bikemaster -Quality affordable parts
bikemaster.com

Dr. John's Motorcycle Frame Straightening
Singlehandedly responsible for putting the MB5 project back on track!
drjohnsmfs.com.com

Sudco International
Replacement electrical components, Mikuni VM22 carburetor, perveyor of quality replacement parts for vintage bikes
sudco.com

Michelin Tires -Gazzelle moped tires
michelinmotorcycle.com

Caswell Plating
Epoxy tank sealant - the best there is!
caswellplating.com

Treatland.tv-Malossi
70cc kit. Moped parts superstore.
treatland.tv

Perk LLC -Case Gaskets and technical advice. Supplier of hard-to-find moped parts.
perkllc.com
(317) 371-8530

Rusteco-Rust Removal treatment for the MB5's gas tank.
rusteco.com
(800) 787-8326

Haynes Manuals
Invaluable technical information and diagrams.
haynes.com
(800) 242-4637

Huntington Beach Honda
Various OE parts such as gaskets, grommets, and seals. hbhonda.com
(714) 842-5533

Mechanical Meditations
Mechanical MeditationsMotorcyclist
Mechanical Meditations
Mechanical MeditationsMotorcyclist
Mechanical Meditations
Mechanical MeditationsMotorcyclist
Mechanical Meditations
Mechanical MeditationsMotorcyclist
Mechanical Meditations
Mechanical MeditationsMotorcyclist