1913 Veloce motor disassembly
The motor came apart easily, even with all the dried up grease on the crankcase screws. I’m now measuring up the various bits, deciding what needs to be rebuilt, replaced or used as is. The cast iron piston is in very good shape. Just a few small scrapes on it.
The good news is that the motor is complete, with all parts. And none are broken. Some are worn, but that is to be expected. As this bike will be kept forever, I’ll be replacing bearings, etc as a matter of course. My kids can fix them again in 30 years when the bike belongs to them.
Compare this motor to the 1913 Premier in this article. Piston is different (three top rings vs one top and one bottom), magneto is out front, etc.. And of course the cams and followers are completely different.
The Veloce motor will look very familiar to owners of a Trusty Triumph! (PS, if you have a pre WWI Triumph, please contact me via the comments link).
Cams are internal on the camwheels. Not much of a cam profile, just a fairly simple cut. But there isn’t much room to increase the lift by changing the profile. Cam followers are hardened rollers to reduce wear. As they roll, they do not skid on the cam, which makes both parts last a lot longer. The ‘16 Excelsior has a similar setup, but with conventional external cam lobes.
The upper end of the cam followers (rockers) have a hardened flat that lifts the valve tappet. Tappets ride in long bronze bushings in the crankcase. Then the tappets lift the valves. It all adds up to be a lot of rotating and reciprocating mass, which moves with ever other rpm of the motor. Accelerating and decelerating that mass takes power! And each bushing has some friction… Overhead cams eliminate a lot of this stuff, which only helps their power output. Desmo types even eliminate the valve springs, which is bit more force, a bit more power. Ping me if you’d like further details on this stuff. I’m a bit too busy with the project to do a full article today on OHC benefits. Some more cam stuff is here. Or read some of Kevin Cameron’s articles in Cycle World.
This is a clever method to keep the pinion gear on the end of the crankshaft. The shaft is hollow with an internal taper, and the draw screw has an external taper. When the screw is tightened, it forces the crankshaft to flex outward, locking the gear in place. To time the gear, a small key fits into one of the expansion slots in the crankshaft. It is basically the same setup that Bridgeport milling machines use to hold cutting tools in the quill, an R8 taper. Since the screw is held tight in the taper, it does not have to be a left handed thread, which makes it simpler to cut the thread and to source a replacement screw if needed. You’ll recall that the left hand treaded screw on the Premier came loose in the Mohave desert and did some damage…
One small puller was needed to remove the inner half of the engine pulley from the crankshaft. When you do this job, be sure to use the correct puller. Don’t be tempted to use two screw drivers and pry it! And you don’t have to spend a fortune to get the right tool. Just $5-$10 at Harbor Freight for a semi-disposable tool. Better ones are available for a price from all the good tool shops.