[How To] Built my own topcase carrier

elizilla

Guest
(from the other forum, where I posted this on 4/25/2010)

I decided to build my own topcase rack, because I think I can do better than what I've seen ready-made.

I purchased the following:

1. Aluminum flat stock from McMaster-Carr. 3/8" x 12" x 12". 3/8" thick is overkill but I wanted to be able to countersink the holes so the screws didn't stick out. This slab of aluminum was a bit heavy, so I ground away some of the excess metal from the underside, in the areas it wasn't needed, to reduce the weight.

2. SW-Motech Givi adapters. They sell these for their quick release side racks. It's the hardware needed to attach Givi cases. I didn't buy the rack, just this adapter kit. It's got enough parts for two cases, but I only need one. I'll save the others - I have a bad habit of buying bikes that don't have good aftermarket support, so I'm sure I'll do this again eventually.

3. Honda part number 61304-165-013, the square nuts that fit to the underside of the grab rail. They proved hard to find, but this seems to be mainly because the two dealers I talked to were both idiots. I eventually sourced them from the UK, but I've since learned that other people have gotten them from US dealers, so it can be done.

4. A bunch of misc spacers, washers, and bolts from my very good local hardware store, where they have a whole room full of such items.

5. A rattle can of black bedliner from my local auto parts store.

I have a friend who has some machine shop tools. I used his milling machine, drill press, and grinder to build this. I'm a slow machinist so it took me two days, sigh.



There are four mount points on the tail of the bike. Two are visible in stock form. You have to drill holes in the plastic piece on top, to get to the others. The spots are marked on the underside of the plastic, so this isn't too hard.

I built it so I can move it forward and back. When I have a passenger, it can be placed all the way back, so they can lean comfortably on the case. When I am riding solo, I can move it all the way forward, which places it half over the passenger seat. I'd have had to make it larger, to get it all the way forward, and I decided it was better to keep it to a size that doesn't stick out from under the case. If I strap a bedroll in front of the case, I can lean on that. And as long as I was going this far, I included two in-between positions, just in case I decide I need one.

All I need is a 5mm allen wrench to move the carrier. The square nuts have fingers that hold them in their place on the bottom of the grab rail, so I don't have to get a tool in underneath to loosen/tighten the fastening bolts. I did put some duct tape on the underside of the square nuts, just so I don't accidentally rattle them loose and drop them into the black abyss. You can't see the duct tape from outside, and it's not structural - it just keeps the nuts from dropping when I pull the screws out.

I made slots for two of the mount points, and holes for the other two. I thought about making slots for both but decided they were too close together, and that having holes for one set would be stronger. So two of the screws have to come all the way out to move the carrier, but the other two just have to be loosened. The holes and slots are all countersunk so the screw heads don't stick up above the surface.

The Givi case has three mount points. There are two mushrooms that the case slides onto, then it snaps down onto a triangular wedge. The mushrooms are 22.5cm apart, center to center. Those were easy to place. Once I had them placed, I used silly putty to find the spot for the wedge. I made it into a pancake and stuck it to my aluminum flat stock, in the vicinity I thought the wedge needed to be attached. Then I pushed my case onto the mushrooms, and mashed it into the silly putty. I lifted the case off and set it aside, and I could see where the spot on the case was, that the wedge fits into, impressed in my silly putty. I then placed the wedge in that spot on the silly putty, and pressed it down. When I removed it, I could see where the mount holes on the wedge should be. I used a tiny screw driver to push through the silly putty and mark the surface of the aluminum with scratches, in those spots. I peeled away the silly putty and drilled the holes in the scratched spots.

I cut some of the aluminum away from the margins, so the lines of my carrier follow the lines of the bike. And I drilled a bunch of extra holes around the perimeter, that I can use to strap things to it when I am not carrying a topcase. I used the grinder, then a file, to clean up all the edges. I painted it with the bedliner paint, which has a pebbly finish that blends with the rest of the bike, and hides my less-than-perfect millwork. Now if only there was a way to hide how bad I am with a rattle can!

Here it is mounted in the rearmost position:


Here is the forwardmost position:


And here it is with a topcase on it, in the forward position:


I'll run with it for a while, and see how I feel about it. I have the extra parts to make a second version someday, if I come up with any better ideas, or if something about this version turns out to be irritating.
 
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elizilla

Guest
Update on this, as of now...

The bedliner paint didn't adhere well - it has chipped off like crazy.

I'm still pleased with this topcase carrier. I find that I rarely move it, though - it's too much trouble. Still, it's nice to set it all the way forward, when I'm loading up the case for a trip, and leave it back when I am riding around town, rarely carrying weight, and might pick up a passenger. If I built it again I would skip the countersinking - it's not needed; the case sits up high enough to clear the screw heads. And without the countersinking, I could use slots for all four screws, which would make it easier to move back and forth. I would also make the bungie holes larger - it's a pain trying to feed the loops on my Rok Straps through them.

Note the forwardmost position is still not far enough forward to lean on the case as a driver backrest. I could build something strong enough, but it would transmit more stress to those mount points, and I don't think that what you get, on the bike itself, is strong enough to be cantilevering a topcase that far forward, so I didn't do it. If I can figure out a way to put some of the weight onto mount points that are farther forward on the bike, I might do it later.
 
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elizilla

Guest
Oh, and here's some more info I posted, farther down the thread about this:

The most difficult pieces to source, (besides the weird Honda square nuts discussed up-thread, that the Morley's dealer in Houston was so helpful about, and my dealer was so unhelpful about) were the spacers that fit in the extra holes in the grab rail, to keep it from being crushed when you tighten things down against it. There are four structural holes that the carrier plate fastens to. These holes go through the plastic arms of the grab rail that are under that decorative black cover. Metal sleeves are needed because if you just run the bolts through the plastic, it's not going to be durable - the plastic will squish and crack. These metal sleeves are hard to find. The stock bike has hardware in two of the holes already, but you need slightly different hardware for the two holes that are only used when you mount a topcase carrier.

Measurements:
Inner diameter: 8mm
Outer diameter: 12.5mm
Length: 13mm

I was unable to source these even at my really good local hardware store. And if you run without them, it will stress that plastic too much. So, McMaster-Carr to the rescue! I found this part number at their site, for a spacer that matches: 91868A250. They are $9.66 for a package of 25. I have spares. Anyone who needs a pair can drop me a PM.
 
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elizilla

Guest
The holes are for lash points. I did remove some excess material from underneath, to lighten it, but I didn't grind all the way through.
 

dick czmo

Guest
elizilla, i live in the Portland, Oregon area and have been trying to get the two square nuts for the underside of the grab rails. The local Honda dealers have been no help. Could you give me the info on where you acquired these nuts i would appreciate the help. DC
 
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elizilla

Guest
Dick,

Here is the page in the part catalog where they live. They are part #3. When I was doing this last year, that part catalog just said "Call for price" and when I called they were helpless. But I see it has since been updated, and actually does contain a price. Also, I think it was Andy Morley who reported that his dealer was able to get them for him, so perhaps Honda USA has got the supply chain worked out.

What I ended up doing last year, was ordering them from England. Which was expensive and slow. If you can source them on this side of the pond, that's probably better. Why don't you try ordering from that link, and let us know how you make out?
 

DirtFlier

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The installation instructions for the base that supports the Honda top case has no part numbers assigned to the individual parts so it's difficult to imagine being able to order the square nuts through a Honda dealer. I made my own Givi V46 rack adapter using small diameter, square steel tubing.

Katherine - in ref to the crinkle, bed liner paint, I was thinking of painting my bike trailer with that stuff. What made it peel or chip?
 

Igo

Guest
You can get them from your Honda dealer. Take this part number to your dealer and give them $13 for the $4 worth of nuts and they can get them directly from Honda.
61304-165-013
 
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elizilla

Guest
The stock bike has four slots where the nuts fit. Two of the slots already have nuts in them, to hold the plastic on the tail. So you just need two additional ones to get to four total.
 
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I recognized this was an older thread but I'm looking for a way to reduce/minimize the vibration in the topcase assembly. I built the assembly last year, long before I heard about this forum. I'm using the Honda topcase rack, inverted, with a Pelican case mounted to it. No need for details here, but the rigidity could be improved by a different rack.

You've probably had some ride time with it. Is your design as solid as it appears to be? What would you do differently?
 
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elizilla

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I would either give up the sliding functionality altogether, or use four slots instead of two - taking those screws all the way out to move it, is a nuisance, and with it forward it blocks me from getting under the seat. It would also be nicer if I could build the slider functionality so it doesn't require tools to move, but that gets way more complicated in a hurry.
 
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elizilla

Guest
I know what they look like, I have had a Russell seat with a backrest. :) And that is the sort of thing I've been thinking of - the good hardware store near me has drawers full of such items, so they're easy to get. The tricky part is where to put them. Right now my adjustment is also my attachment point, and there's no room for knobs there because the case sit flush on top of it. The knobs have to go somewhere else, which means I need to make some kind of base that bolts to the bike, and a rack that slides on top of it, and maybe have the knobs stick out the side or the bottom? And all of this without making the whole thing too much taller, or getting beyond my abilities as a machinist. Lots of things to consider.
 
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Great feedback, and the "knurled knob" (that's what I've called them since the submarine days) idea is an outstanding one. I've got a Bun Burner 1500 planned to see my son in Reno. Perhaps if I catch up with my domestic delinquencies and let the NT cool awhile then I can improve on my topbox assembly with your ideas.

Thanks.
 
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elizilla

Guest
I'm cleaning my workbench, trying to avoid leaving the place looking like a toolbox exploded. Amongst the remnants of defarkling my NT, I have a couple of extra pairs of the special nuts, Honda part number 61304-165-013. Anyone need these? I'll send a pair of the sleeves with each pair of special nuts, these are McMaster-Carr part number 91868A250. Once you have these, everything else you need to make your own topcase carrier or mount something generic, can be sourced at a good hardware store - these are the only super unusual items. Free, as a community service to this great forum; all I ask is that you post pictures and/or descriptions when you're done. :)

First two PMs get these. Note that I'm leaving town tomorrow for ten days, so you may have to wait a bit to receive them.
 
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I did the same kind of thing when I mounted the JC Whitney base plate, ie, moving it far forward. I knew that it would interfere with removing the seat so I make sure to carry the proper wrench with me at all times (12mm in my case). I was also paranoid about those pesky little square nuts becoming lost when I had to remove the base plate. So, I used some RTV when I put them in place. It makes sure they won't fall out when the base plate is removed.
 
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elizilla

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I just found this. If I were to do this again someday I'd seriously consider using it for my slider functionality. In fact I am tempted to just order some even though I'm not currently doing anything like this. :)

 
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Why not get two bottom mount drawer slides? You can get different lengths, they are designed to separate top and bottom, and are fully capable of much more weight than we have to deal with. I may start looking at that solution for mine as well. I like having the box forward, but, need to be able to remove the seat or move it back to carry an extra duffle.
 
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