Al Lighton’s Inner Hard Bag Repair/Reinforcement/Upgrade


10/18/2008 16:32

As posted on Bad Weather Biker’s Website

S3 Saddlebags look pretty nice when mounted on the bike, but the mounting method leaves a lot to be desired. The inner part of the bags are made of ABS plastic and "hang" on indentations molded into that ABS. Metal/plastic draw (or knurled knob) latches keep the bags from coming off those indentations but don't take much of the load as the ABS. They do concentrate the load points and provide some stress risers and it is common for the bags to crack at the latches. As the bag flexes, the ABS is overstressed and cracks occur at the latch points. There are only 4 points of attachment - 3 latches and a bumper. Early bags didn't reinforce that bumper area and the result was usually a hole worn right thru the ABS.

Buell has replaced many failed inners under warranty but it apparently is difficult to get these replacement parts now. If you aren't the original owner with an intact warranty - forget it, it isn't going to happen. If you try to buy them, get ready for some serious sticker shock.

After encountering these difficulties the correcting and repairing the bag's deficiencies seemed the only practical remedy.  This article details how I went about fixing Reindog’s (Tom) and my saddlebags by fiberglassing the inside as a doubler. I did this as a result of a suggestion by Steve Slaughter, and I'm pleased with the results. I should note that only my right bag was damaged, but I highly recommend doing this to all bags BEFORE the bag fails/cracks.

The following photos show some of the typical problems. My bags came from a cheat on eBay who didn't tell me about the damage. The rear bumper plate on the right bag was missing, and the bag was very cracked up at the corner near the bumper. Although it is difficult to see in these photos these cracks were all the way thru and splintered.


 My right bag had a single crack radiating out from the front cam latch. I accented it a little in the picture to make it more visible.

 Tom's bag was very cracked up at the rear latch. Several cracks radiated from his latch. We found some other cracks not visible in this picture as well.

 The Repair and Reinforcement

The first step in the repair is removal of all the inner bag hardware. I removed the latching plates (that hold the outer bags closed to the inner bag) from my bags.  We were able to repair Tom's bags without taking them off.  The cam (or knob) latch hardware that mount the bags to the bike must all be removed as well as the bumper plates.


Next, sand/Scotchbright the entire inside surface that will be glassed. This is to provide a surface that the resin can adhere to.  After “roughing up” the surfaces, wash out the insides with soap to remove all the dust and grease.  It is important to do a thorough job of this as you will want these surfaces squeaky clean. You can see the crack in my bag in the second picture. More Scotchbrighting was needed there to guarantee adhesion.


Next, tape up the latch holes and cracks on the backside with masking tape so that the resin can't escape. The goal here is to provide a single layer of fiberglass over the entire mounting surface, and a couple more layers at the stress points. However, because the cam latches have a fixed grip length, if you build up the thickness more than a few layers the latches won't work. The factory counter bores the latch mounting point to make it flat and the right thickness (see two pictures up), and this contributes to the cracking problem. We can't do that here or we'll lose the strength we add.

I used epoxy resin obtained from a marine hardware (boat-type) store. The stuff is expensive, about $65 a gallon with $20 additional for a quart of catalyst. I read that the much cheaper polyester resins ($25/gallon at Home Depot) MAY work better because they will melt into the ABS a little. I was scared of melting too much of my saddlebags, so I used the epoxy.   My research told me that the epoxy resins are generally stronger and less brittle. There are different weights of glass cloths; I used the medium weight stuff at the marine supply place. Use woven cloth, not random fiber mat, as it is thinner.

I cut a few small pieces for reinforcing the latch points, then put down one big piece in as a continuous doubler. You want to put the small pieces UNDER the large piece.  As you wet it out, some fibers will fray on the edges. Laying the loose pieces under the large piece minimizes the fraying.  See “Note” Below

After laying all the glass in place, I mixed up the resin. I used measuring cups to get the ratios right, but for $20; you can get pumps that properly dispense the right ratios. The next time I go through this I will make an additional investment in the pumps


I used large Ziploc freezer bags for mixing the resin. After pouring the measures of resin in the bag, kneed it thoroughly to get the mixture completely mixed. This is a great way to get thorough mixing and it without making a mess.  When done you can just throw away the bag along with any of the resin you do not use. 

Pour the resin into the saddlebag. It helps to have two people for this; one to pour, and the other to work the resin into the cloth.  The goal is to get the glass mat completely wetted out and laid up to ABS surface without air bubbles or ridges. It will be difficult to get the resin impregnated fiberglass completely seated in the right angle corners, do the best you can. USE RUBBER GLOVES. This stuff is NOT good for your skin and although infrequent, severe allergic reactions can result from direct contact.  Some people are so allergic to this stuff they will get a rash if they're even near it – your mileage may vary (YMMV).


In a perfect world, the whole mess would get a “peel ply” put over the fully wetted out mat, and then the surface would be "vacuum-bagged". This is just a plastic bag that is evacuated, causing the atmospheric pressure to force the excess resin up into the peel ply. After curing, the peel ply is removed, taking the excess resin with it and leaving a reasonable surface. The vacuum bagging adds strength. But I did none of this. I just used lots of paper towels to blot out the excess resin. The excess resin will add little strength, but adds weight, so do the blotting until you can see the cloth texture. It is easier to wet it out with excess resin and then remove the excess with the paper towels than it is to put just the right amount in to start with.

At this point it's ready to cure for 24 hours.   What it looks like now will be what it looks like when it's cured, so make sure you're happy with it. After curing, there will be little bumps and SHARP glass splinters that may be sticking up. A dremel tool will make quick work of them. Be careful, they will slice you (or your bag liners) until you remove them with a sander.


NOTE: After I did all this, I came up with a brainstorm. The molded in ABS ridge that the saddlebag hangs on forms a little trough inside the bag. Nothing gets stored there, it's dead space. I figure that anything that could be done to reinforce that ridge is a good thing. So I bought a short length of nylon rope, mixed up some resin in the bag and worked it into the rope as best I could. I then laid the rope in the trough, and then filled it with resin all around it. It adds a little weight, but makes the bag extremely rigid in this area. If I had it to do over again, I would have put the rope in at the same time I laid in the cloth.  I did it as a second step 24 hours after the doubler layers cured, after roughing the surface of the doubler layers up a bit. Note the paper towel "dam" to keep the resin in the tough with the rope.

After the work has cured, reinstall the cam latches and drill/mount the bumper reinforcing plates with a pop rivet tool.   Getting the cam latch plates (the ones that engage the mounting frame on the bike) in the right position on the threaded shaft takes some adjusting.  You may have to eliminate the assembly’s lock washers to adjust for the extra thickness of the fiberglass.  If you eliminate the lock washers,  I STRONGLY recommend using red Loctite on the nuts that retain the cam plates.