Having addressed in detail rebuilding a Gold Star's magneto
, 6-spring clutch
, and gearbox
that leaves the engine. So, this is the first of what will be five separate threads covering the entire rebuild of a Gold Star engine (or any pre-unit B-series single) based on my rebuild of a BB34A. A few months from now, when I hope to have finished this sequence, it will have separate threads detailing the step-by-step rebuild of the:
Although there are a few detail differences (e.g. breather and rocker boxes), for the purposes of rebuilding an engine the procedure is essentially the same for all Gold Stars from the late ZB with separate rocker box through the DBD. Even with the one-piece head and rocker box the early ZB is essentially the same as well. Further, although my 1956 BB34A "Alloy Clipper" engine has a 'B33' bottom end so is lacking a drive-side bearing retaining plate, otherwise the engine is basically the same as a BB34GS (nb. this plate is shown in the Spares manual for the B32 and B34 so variations exist).
The next three images show, respectively, the bottom ends of a BB34A, BB34GS, and DBD34GS.
Comparing these three images in detail shows the great similarity of all three engines. Because of this, even though my 1949/56 BB34A-based "Alloy Clipper"
is in the Projects forum it seems worthwhile to repeat the engine rebuilding information here in expanded form, pointing out where any important differences affecting the rebuild of a Gold Star engine exist (e.g. lipped inner roller bearing on my BB34A whereas Gold Stars have larger, non-lipped bearings).
Since my BB34A came to me in pieces, each thread in this series will be the inverse of usual rebuilds, i.e. they'll end with 'disassemble in reverse order'. Also, as people add to, or correct, what I've written I'll make the appropriate changes in the relevant posts so the information in this thread will be as accurate and self-contained as possible. However, this has to be done within the 5 images/post limitation so I already know that breaks between posts won't always be in ideal locations. Finally, I supplemented the photographs I took while rebuilding my BB34A with additional photographs of parts from the shelf, some of which aren't in great condition, so don't assume all of them are from my engine.Assembling the Bottom End
If you follow the 17 parts of this section in order it will keep you from having to unbolt something you've already bolted together as you assemble the bottom end.Supplies needed:
-- Assembly lube
-- Camshaft lube
-- Yamabond 4 or equivalent
-- Permatex Permashield Gasket Dressing and Sealant
-- Loctite 262 (red, high strength)
-- Loctite 680 (green, retaining compound)
-- (2) Sump gaskets (or gasket material to make your own)
-- Timing cover gasket
-- Oil pump gasket
-- (2) ¼-20 UNC socket head cap screws or BSW bolts drilled for safety wire
-- Safety wire
-- Oil seals for cams and crankshaft in timing cover (two for BB and three for later models)
-- Oil seal for magneto pinion
-- Tape or rubber bands to hold studs1. Inspect all mating surfaces and clean and deburr all tapped holes. 2. Rebuild, true, and balance the crankshaft for the piston that will be used.
[this will be the subject of a separate multi-part section in another thread that I haven't written yet]3. Inspect the following:
-- Condition of tappet faces, and ensure they have minimal runout when rotated. I don't know how much wear is acceptable, but I didn't bother refacing ones for my BB34A that were worn by ~0.002" in the center.