Bottom End Build: Day Off Crankshaft Work

With a day off, decided to attack the crankshaft swap.  Needed to take the "good" one out of the display engine to use in the real bottom end.  I'd put the "bad" one into the display.

Here's why that crankshaft is a no-go:

• It has holes drilled into the flywheels which means it would throw off a stock motor.
• A standard piston pin doesn't fit through the connecting rod!!

The swap went relatively smoothly...

• Added the new woodruff key to the bad crank so I could fit the rotor.
• At first couldn't get the cases to close on the new case but just did it again (and a couple times more).  Just need to get the "feel".
• Installed both thrust washers on the good bottom end.
• Be conscious of the 2 thrust washers on the two sides of the kickstarter gear.
• Ran into a weird problem where I couldn't get the tranny to fit.  Need to make sure to turn the shift drum to full counter-clockwise before installing to set the gears in an optimal position.

Bottom End Build: Busy Sunday

Lot of good work today on the carpet (and in the kitchen).

New toy is an infrared thermometer.  Combine that with the heat gun and use it to heat up the case to install the bearing.  All sounded good in theory, but wasn't sure it would work in reality.  But actually everything went perfectly to plan.

Heated the case with one hand while taking the temperature with the other.  Heated it up to about 215 and it didn't take very long at all.  Did this on top of the stove (on a baking sheet covered with tin foil).  Meanwhile had the 6004 bearing in the freezer.

As soon as it hit 215, I moved the case down to the floor (on top of plywood) and knocked the bearing into place with a 29mm socket with just a couple taps of the dead blow hammer.

Almost too easy, but job done.

Thought about removing the old bearing on the other side and installing the new one, but realized that I didn't have a socket big enough to safely knock the bigger 6204 bearing into place.  Need to get about a 32mm socket or maybe a dowel of equivalent size.


Brought up the crankcase for inspection.  This is the one with holes in it.  Don't know why it never occurred to me before, but now I assume that the holes are a custom mod, not a different type of stock crank.  Did the inspection as per Clymer's and it was all well within the wear limits. 

Broke out the Tusk tools and installed the crank easily.  Actually got the entire case all the way back together but then had second thoughts.  Not really sure what the effect of the drilled flywheels will be on a stock setup and may not be worth the risk.

Thought about pulling the crank from the model engine and swapping it with the custom one, but honestly just too much work!


Ended by swapping our the rusted cable arm on the clutch cover with the one from the model engine.  Learned something new: there's a little clip on the arm that holds it in place.  Easy to miss if you don't know it's supposed to be there.

Motor: Holey Cranks

Downstairs just long enough to take this side-by-side of 2 cranks showing the differences in the flywheels.

Some debate on the Yahoo Group as to whether the extra holes are for purposes of balancing or whether they help with assembly (alignment).

Spares: Cheap Parts

Unboxed a couple items today: the $15 cylinder for use as a prop, and the $20 eBay crankshaft.

The cylinder was in rough condition, but that's exactly what I was looking for (and what $15+$12 shipping will buy you).  I wonder if it can be re-bored down the line, though.

All I need is a head cover (on order) and Ivy will have her mock engine.

Might even install this crankshaft.  It's got some light surface rust and one bearing turns very roughly, but should be fine as a "placeholder" part.

Also measured all the cylinders and heads I have and they are all 65cm diameter.  Hoping that means that Astrid's cylinder will also fit onto any head.  What about bottom end, though?

Spare Engine: Puzzle Pieces

Did a little inventory of the other parts that came with the spare bottom end.  So looks like I have:

1. left and right crankcase
2. complete transmission (but missing the thrust washer)
3. kickstarter
4. primary driven gear and circlip
5. clutch basket and hardware
6. crankshaft and connecting rod
7. cam assembly (no chain, but one came with Roxy's spares)

The oil filter in the clutch basket.

Assembly of the kickstarter.

Took awhile to figure out where this bearing went.  For reference, it goes on the end of the countershaft into the recess in the left crankcase cover (on the opposite side would then go the chain sprocket).