Motor Part 3: Reassembly and Regulation

So, we have the motor components all done.

Let’s reassemble the motor and get this sucker running!

If you have been careful in documenting how you took everything apart, then putting it all back together should be a snap! If you haven’t….well, consider it a free lesson from the school of hard knocks. As we say around these parts: “that’ll learn ya!”

To summarize:

• stripped down the trunk, repaired any damage, sealed channels, lapped and lubed the face
• recovered, lapped and lubed slide valves
• repaired, rehinged and recovered pneumatics
• clean and polish all hardware
• replace and lube all bushings of various flanges, arms, valve guides

And so. After verifying each individual pneumatic independently for airtightness, let’s glue them back on to their home base. Probably good to get that out of the way, right off the top. You don’t need to get fancy or have an awful lot of pressure in this situation; here’s my solution:

gluing and clamping pneumatics back on air motor

Now with that done, test again, to make sure pneumatics are still tight. Close them and then seal all the trunk intake channels. If they offer stiff and continued resistance as you pull them open (firmly, but gently), and you don’t hear any hissing, leaking noises, you should be good. If ever you get the odd leak at this stage, you can probably bet (by process of elimination) that it is between the pneumatic and the trunk. If you can localize it you should be able to then neutralize it, with a few drops of Phenoseal — ask me how I know! (wink, nudge)

Now remount the hardware, again being careful not to bend the crankshaft as you reassemble everything. Next the slide valves. And you’re done! Or are you?

Last but not least, let’s check the timing. As with comedy, timing is everything! There is a mechanical sweet spot to be had, where the motor works at optimum efficiency (just like any combustion engine, including the one in your vehicle).

There are a couple of different ways to look at this, but basically you want all the valves set the same, and you want them all to begin the “powerstroke” just after the valve closes. You can refer to Reblitz 41 for more details, or also John Tuttle’s tidbits here, or here.

Once you feel confident, you can take it for a test drive! It should run fairly smooth, even at very low speeds. You can use a vacuum cleaner if you don’t have a test pump, but note that this is not the ideal testing device. It may make the motor appear to turn in a lurching manner. I have read that most of the good motors are overengineered to run even if not perfectly regulated, so as long as you get it as good as you can, that’s probably good enough!

Here’s what mine looked like, as an initial test run after rebuild: