May 4th 47UL update: — Linn Motorcycles

Been awhile since we posted anything on the build, so here’s what’s been going on:

Time takes it’s toll, I now use an electric hoist to move the engine from the workbench to the bike chassis. I have the hoist on a trolley so I can lift the engine from the bench, roll along the trolley track, then lower it to the bike frame.

In place, and no paint was sacrificed from the frame in the install!

My build cart is an old railroad baggage cart with big cast iron wheels with molded on rubber tires. I sectioned the cart lengthwise and narrowed it in width to make the size I figured would work best. It also gets a fresh coat of paint every time I use it with my frame rotisserie bracket which fastens to the front. (you can see the stubs the paint frame fit onto is at the right of the pic.

Here’s the hone all goobered up with lapping compound ready to be inserted into the rear exhaust port to enlarge it so the exhaust pipe will fit.

Part of installing the engine is getting the exhaust system to fit. That’s best done when you’ve just dropped the engine in and you’ve got room to see what you’re going to have to bang on to make stuff fit.

The front pipe wasn’’t too bad, only had to make a crease in it where it passes under the motor mount bracket. The frame is actually built to panhead specs, so a flattie motor needs a spacer under the front motor mount for the motor to fit properly. This however, raises the front exhaust port, so the pipe won’t clear the motor mount. Maybe I’m being too kind to Vtwin, but anyway, the front pipe got an extra crease to clear the mount.

However the rear pipe just wouldn’t go into the exhaust port. So reluctantly, I decided to clearance the port rather than try to grind down the pipe. Thus the tool on the drill. The mandrel is actually a 45” mainshaft race shrunk onto some miscellaneous bar stock pieces kicking around. I tack welded stuff on the end just to keep it in place. I figured I would need something pretty hard to stand up to the lapping paste and actually cut the cast iron port. Thus, the bearing race. It did the job, removed a few thousandths and got the pipe to fit.

65A GENERATOR MODIFICATION FOR EARLY 1/4-24 MOUNT BOLTS

Pattern jig on top of end piece to be modified, offset in pic to show amount of mount hole shift.

Here the pattern is positioned over the end cap to be modified on the mill. Just used dead reckoning to position the drill.

Finished end cap with 1/4-24 tapped holes.

I had decided to use a 65A generator on the bike, but am not totally happy with the 5/16 -24 thread insert to allow using standard mounting bolts. So, I decided to see if it was practical to easily move the mounting bolt holes and add a fresh set of mounting holes. Turns out, not a problem, plenty of meat in the casting to get a good set of threads tapped.