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Challenge with rebuilding a 1976 750 Supersport

cary911

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I am almost complete done with my rebuilding of a 1976 Cb 750 Super Sport. Last time it was licensed was 1990. Stored in a damp basement until I rescued it in 2015. I only have body parts to finish and a little electrical work. The original seat was covered in cat claw holes and the seat frame was rusted and not usable for recovering so I bought a new seat from 4into1. Product quality is good, seat frame is plastic. For those of you familiar with the Super Sport from 1976, you might remember that there is a section located directly behind the seat made out of plastic. It is a small storage compartment and is suppose to be attached to the end of the seat and rotates up with the seat when the seat is lifted up. The problem with this seat is that there are no attachment locations on the seat to secure this plastic compartment to the seat. Anyone out there run into this same problem and come up with a solution? I really want to maintain the look of the back so leaving it off the bike and leaving the back end naked just doesn't look right. It's interesting that the seat I purchased is molded to take the plastic compartment but did not create any attachment points. The new seat has attachment points for the hinge and locking pin but that is it. Again, any suggestions would be appreciated.
 
There's a few different styles of fasteners of this type. Rivnut is the most common, but the Versa-nut looks like it has a larger flare on the backside that would give more support in the plastic pan than a standard Rivnut. Be careful when drilling the pan that you don't drill through the cover!

They should not have to be very big. The stock mounting studs and bolts for the tail section were only 4mm in diameter.

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May find something in a well equipped Ace hardware store, I've found several fasteners of that type at mine. If the plastic is thick enough and solid enough, may even use short sheetmetal screws like used to replace the plastic 'cutting' screws specific to myriad car parts now, the plastic screw is essentially a sheetmetal screw with modified threads. I use sheetmetal screws all the time on plastic parts on cars now and sized right they last forever. Any hole needs to be properly sized to not be too big or small though and easy.

I use fasteners of that type all over my crackerbox cars now to replace the stupid one time use pop fasteners the OEM uses, I commonly bolt parts down much more solid.
 
I can't get the Versa Nut USA distributor to answer their phone so I tried the Fastenal store near me. They don't carry the product and don't have anything like it. Thinking about a nylon washer as a backing plate and a nylon nut epoxied to it and then expoxying the washer to the seat bottom. Thank you guys for your thoughts and recommendations.
 
Shouldn't work, for one, true nylon is an oily based plastic and generally epoxy doesn't hold it for spit. BTDT. Depending on the plastic used on seat same issue. Unless you can get between the seat plastic and the foam to get the nut on backside of seat plastic. You said it was a complete seat though.

http://www.acehardware.com/product/index.jsp?productId=1292485

Look at Hillman parts there, and they come in more than one size and depth, you'll want shallow. I've bought some there that once collapsed only stick in the foam maybe 3/8" inch or so. Boxes there but they sell them individually as well. The picced part in link is long but the long screw then pulls it to very much shorter and the sharp teeth under head lock it into place. The teeth point straight down but you can make the bite shallower by bending them around a 45 degree angle to still bite enough to collapse the part, then you toss the longer install screws and use much shorter ones that don't poke up into your plastic seat as far to not puncture the cover from below. Installed correctly those parts will hold a great deal of weight, I have them holding entire bumper covers on cars when the OEM pop fasteners turn into loose rattling crap after the second use. Pop-in type OEM fasteners are not intended to be reused.

I went to custom one-off 3 inch long pods instead of 4 inch on my CB550F (inside spring rebent and cut and outside foam too) and kept the OEM airbox in place which then became a stashbox for plugs, wrenches, parts, etc. I plugged the front where the air cleaner main boot left a big opening with those Hillman fasteners. Also used them to plug the top air duct hole to box too, the box became 100% waterproof with some rubber gasket added made from tire tube material. Looks like it came OEM on the bike.
 
I think the biggest problem you are going to have with any expanding/crush fastener, even the versa-nut that I linked to above, is that the area of the seat you are going to want to fasten to happens to be the point of thinnest foam. There is not much space between the seat pan and the cover at these attachment points and there may not even be enough room to accommodate the collapsed fastener, let alone have enough room to insert the fastener in its fully extended state.

How is the cover attached? Can you dislodge the cover, insert a fastener from above the seat pan, then reattach the cover? Maybe consult a local automotive/marine upholstery shop?
 
I may have to find a local upholstery shop. I am currently not real happy with the matching up of the two contours between the end of the seat and the beginning of the storage compartment. I have finished painting the hinge and lock and will mount the seat on the frame to start seeing what adjustments I need to make to the compartment. Temperature here in North Carolina has been in the 90's for the last two weeks and been sort of tough to work in the garage. Looks like middle of this coming week temperature will lower into the 80's and I can get back to the challenge. Thank you both for your help and suggestions. DSC_0076.jpg
 
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