Friday, December 30, 2011

I HATE banjos...

I didn't used to, though. Dueling Banjos? Loved it. That was then, this is now - I'll never be able to listen to it again.

Why? Well, it's all because someone, possibly at Rotax, possibly at Van's, decided that the bolts that act as some kind of fuel line crossing guard look like banjos and should be referred to as Banjo bolts. That in and of itself would not be sufficient to induce my ire; no, I find them rebarbative solely because of the nature of the work on them that I did today.

I'm getting ahead of the narrative, though, so let's start at the beginning. I've spent the last couple of days making repeated trips to the hangar and to Harbor Freight (The Home of Un-Pawnable Tools*) in order to gather up the tools required for the installation of the carburetor drip trays. These seemed easy enough but I underestimated the dependency that I have on the tools that are normally available to me at the hangar, and just how many different metric sized tools that would be required.

Finally ready to go, I started on them this morning after one final trip to the hangar for a #40 drill bit (the pre-drilled rivet holes on the trays didn't align very well at all) and a handful of clecos. As it turns out, I grabbed the wrong size clecos, but fortunately I didn't really need them. The trays get four AN4263-3 rivets each, but none of that size are supplied with the engine kit. AN4263-3.5 worked fine. The trays also require a little filling in the corners to prevent any fuel that may drip onto them from leaking out - that was easily accomplished.

That was the easy part. The next steps involve removing the carburetors (one at a time; I started with the left side) and the rubber flanges that hold them onto the engine. This is all started by removing a spring that apparently keeps the carbs from moving around too much given they they are housed in flexible rubber flanges. It was somewhat hard to get the spring off of the little clamp it was attached to, but I consoled myself with the hard-earned knowledge that it would be even harder to put back on. That's just the way these things work, I've learned.


The next step is easy (no, really!) - it's just a phillips head screw that needs to be loosened. You can (and should) loosen it up quite a bit - the screw is captive in the clamp so you don't have to worry about it coming all the way out.


Once the screw/clamp is loose, it's just a matter of rotating and rocking the carb around to get it loose enough to pull out of the flange.


Next, Van's suggests removing the retaining nut behind the cushion clamp that holds the fuel line. If this looks impossible, that would be because it is impossible.


I found it easier to just wiggle a wrench (11mm) back in there to get as much grip on it as possible and use a 14mm socket to remove the bolt. The bolt comes out in the next step anyway, so you might as well just do it now.


When the flange is off, check to make sure that the O-rings are still in place on the engine and in the flange.



The drip trays fit right in. Replacing the clamp was easy; I just used the indentations in the sides where the bolts pass through to align the clamp appropriately.


It all went back together pretty much in way it came apart: the nut was hard to get at and the spring was a real stretch (heh!) to get back on. And, believe it or not, the other side was actually harder. The big ignition module black box gets in the way. Still, I think it was an hour or so to finish both sides.

Then it was on to the banjo bolts. The goal here is to remove the thingy on the top with the black rubber cover over it, remove some kind of restrictor thingy inside the top bolt, and turn the whole remaining mess upside down. Of the three tasks, it is the third that set me against banjos forever.


The assembly is mounted on an aluminum tube, so any torque applied to the banjo bolts needs a countervailing torque applied too in order to keep from bending/crimping/cracking the aluminum tube. So, armed with two metric wrenches working in opposition, I loosened the first bolt.


I removed the black-covered nipple thingy and set it aside. I finger tightened the bolt back in just to keep track of it and the two washers that had sandwiched the nipple thingy.


The bottom bolt holds two hoses. Here's one of them:


The other hose supported by the bottom bolt doesn't move very much - it's still staying in position under the banjo assembly. There is an allen head bolt on top that gets loosened in order to rotate the assembly upside-down. I loosened it and turned everything over, trying to keep it in the same relative position on the aluminum tube.


Before putting it all back together, I had to take the top bolt back out and remove the little restrictor device.



It was in there pretty tight, so I had to hold the bolt with a wrench while I used a small screwdriver to remove the brass restrictor.


When I tried to put it all back together, I followed Van's order of business, which was to tighten the allen head bolt first. That didn't work out. Van's kind of subtly warns that the fuel lines might not line up very well anymore; this, as it turns out, isn't a possibility; it is a certainty. As such, I found it worked better to leave the allen head bolt loose while trying to get the fuel lines back in place. Because...

Remember how I said that one of the hoses doesn't move very far away from where it was when the bottom bolt was removed? Well, that's because it doesn't want to. It very much doesn't want to. Getting the two hoses lined up with the newly located bolt hole while not dropping any of the washers or cross-threading the bolt was enormously difficult, and it would have been more so had I not been able to move the mounting block easily along the aluminum tube. My advice: get the bolt started, then go back and tighten the allen head bolt. Even done in that order, you'll find it hard to get good tool access to both the allen head and the other bolt. How you're expected to use a torque wrench is beyond me.


The only way I could get the allen head tightened up was to use the allen head socket and a wrench:


It took quite awhile to get it all back together, but it was a perfect opportunity to re-learn a couple of valuable lessons:

- coffee will help you think more clearly, but any benefit from that is lost to nervous, twitchy hands.
- it is better that I write about this stuff than record it on video; the language used to encourage hardware to comply with my wishes would result in an R rating.



* We stopped in at a local pawn shop yesterday on impulse, what with our being somewhat curious as to what we'd find after watching numerous episodes of Pawn Stars on the History Channel (oddly enough, unless you consider that a lot of the items they get are of historical significance). While we were there, a guy came in wanting to pawn a bunch of Harbor Freight tools and the pawn guy didn't even want to look at them.

"We don't buy those," he said.

1 comment:

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