Join Date: Jan 2016
Location: North Central Ohio
Budget Topcase Latch Repair
I have recently acquired a 2002 K1200LT. Among other things that need attention, the topcase latch had the typical dogleg broken off. If BMW offered the latch handle as an individual part for replacement, I might have considered that option, but they don't. Therefore, I will share my procedure for repairing the latch on the cheap.
I drilled out the rivets, removed the latch, and studied the latch movement to determine the cause of the break and potential repair options to fix it and keep it from happening again. I am aware of the aftermarket "fix kit" that is available, but I'm cheap and besides, I like a good engineering challenge.
It's apparent that the dogleg, being cantilevered from the thin handle surface, can put excess stress on the thin area of the latch handle. The interesting thing to me is that in most threads that I have read that the assumption is that the load is most severe when latching, but looking closely at the latch motion the stress could actually be greater when opening the latch if the latch is pulled upwards with excess force after it hits the stop.
In either case, it appears that the dogleg needs to be supported more fully and tied back into the main structure of the latch. The aftermarket machined billet "fix kit" looks like it does a great job of doing this. But did I mention I was cheap?
My solution was to cut a couple vertical ribs that are as thick as the dogleg, and extending them the full length of the latch down to the horizontal rib at the bottom. (See first picture.) I cut these ribs out of 1/4" thick steel, but aluminum would likely work fine too. I spent some time contouring the ribs to fit snugly between the dogleg, the horizontal rib, and the latch surface. I then epoxied them in place with JB Weld. (See second picture).
After the JB Weld had dried, I was planning on drilling a couple holes through the dogleg and into the new reinforcing rib so that I could add a couple steel pins to reinforce the dogleg further. But after evaluating the strength of the JB Weld joint, I thought the pins might be overkill.
I cleaned up the rough spots of JB Weld and applied some rattle can semi-gloss black paint. (See third picture). I also decided to tap the top three bosses with 6mmx1.00 threads for bolts instead of trying to get washers and rivets aligned for reassembly. (See fourth picture). Reassembly included the three 6mm bolts at the top and four rivets and washers on the front face.
Picture 5 shows the latch in the open position with a view of the right hand rib. Since I had a piece of scrap metal on the shelf, a half rattle can of black paint in the cabinet, and a few rivets in a jar, this fix cost me next to nothing. The ribs took about an hour to cut out and fit, and it took an additional hour to clean up the JB Weld, paint, and reassemble.