Thursday, December 22, 2011

The Shroud of Culin

Or "The Shroud of Cooling," to be precise.

So, what's the first thing that you expect to do when you receive a brand new, $20-some thousand dollar engine? Well, "tear it apart" probably wasn't your first thought.

Mine either.

But when it comes to this, Van's gets to decide 'if', I only have a say on 'when.'

It starts out easily enough: check the 'clocking' on the water inlet fitting at the rear/bottom of the engine and re-position it if needed.

It needed. But it was a piece of cake.

Then a small harness retaining clamp behind a black box called "the ignition module" is removed and the connectors that attach the wire harness to the module are separated.

The first part of this separation involves disjoining the connectors from a metal bracket. It took me awhile to figure out where to apply the blade of the small screwdriver that I was using and in which direction to pry, but once I figured it out the connectors came off easily.

Then the halves of the connectors are separated. Again, once I figured out how to position the blade, it only took a somewhat-more-than-light tug to part them. I wasn't sure if all four of the connectors needed to be parted, so I stopped after the most obvious two. Those are the connectors that Van's had me mark as A1 and B1. So far it seems as if I made the right decision.

The eight spark plug leads are then removed from the spark plugs. They aren't screwed on like they are on a traditional aircraft engine - just tug them off. I was concerned that I wouldn't be able to get them back to their correct spark plugs later, but it turns out that they are plainly marked.

Once they were off, I was instructed to "Pull the lower harness (it should say 'harnesses') as far up between the cylinders as possible." A reason wasn't given, but it becomes apparent later. A combination of pulling on them from above and pushing on them from below got them snugged up into the gap between the cylinders.

Jumping back to the back of the engine, the next step was to remove two cushioned clamps and a spacer, throw away the smaller clamp, the spacer, and the allen screw that was holding them in and replace just the larger clamp using a new spacer and screw. The original lock washer is kept too.

Once that's done, we have to check the gap between "the trigger coil and the trigger cam."

Yeah, I don't know what that means either. For the curious, Van's suggests searching through the Rotax manuals for more info; I decided to just do it. The triggers in question reside behind a plastic cover held in place with three (metric, of course, much to the chagrin of your xenophobic correspondent) bolts.

As luck would have it, the trigger cam was not aligned with the trigger coil.

Putting them in alignment requires turning the crankshaft, and said turning is made easier by removing a spark plug from each cylinder. The fancy looks-like-something-Harbor Freight-wouldn't-even-give-away-free spark plug removal tool provided by Rotax makes this possible, but not easy.

The crankshaft is turned by placing a couple of bolts in the prop hub and using leverage applied via a BFS to turn the crank.

At which point it's easy to ensure the minimum .012" gap (odd that the measurement was provided in inches rather then millimeters - I haven't looked to see if Van's translated for me) and that a .017" feeler won't fit, proving that the gap meets the .012" - .016" tolerance.

I checked the other one too, but I'm not sure that was required. Van's was a little slopped in their pluralities in this instance.

After that brief diversion, it's back to removing the ignition module. This time there are two bolts to be removed. The first is up on top and easy to find/get at. The second is a little trickier - the bolt is impossible to get at, so we remove the retaining nut (only slightly less hard to get at) instead.



This is when it really started getting scary. The eight screws that attach the intake manifolds had to be removed.

The Harbor Freight allen wrenches came in handy for this. One of the screws was in pretty tight (and there some that weren't tight at all - odd, that) so I used the 'Oomphh' setting on the wrench.

You have to keep a keen eye on these O-rings! One stayed in place, one went with the manifold, and two of them split the difference.

Van's suggests using a cardboard box to support everything as the detached manifold and its pair of carburetors gets lifted forward over the top of the gearbox:

I couldn't get it to even go that far.

The problem was that it was tie-wrapped to the water hoses underneath:

Tie wraps are cheap and easy to replace, so I thought about cutting them, but a glance ahead showed that the problem would soon be mooted by the removal of eight screws, two of which are shown here:

This was made easier by the 'finesse' setting on the allen wrench:

The ball-end lets the wrench work from an angle:

Once the entire top-of-engine assembly was loose, I was able to clear off the top of the engine.

All that was left to do was put a locator mark on this bracket so that it can be returned to the same position:

Use the 'Oomphh' setting to loosen the bolt, then turn the bracket 180 degrees:

Damn! I marked the wrong spot!!

At this point, it seemed that the scary stuff was done.

Ha, not by half!!

The next step was to mark one of the grounding lugs on the starter motor to that it could be cut off!!! I spent a looonnngggg time looking at the drawing:

The superfluous lower mark was just the mark I made to identify the correct appendage for amputation, having not forgotten the incident that resulted in the end of my career in Sports Medicine:

There, now the top of the engine is completely bared:

"Why," you ask? Why does all of that stuff have to be removed?

Well, look back to the title of this post. For our next trick, we're going to fit and attach a cooling shroud!

Well, that's not entirely true; first I need to work up the nerve to cut that grounding lug off of the starter motor.

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