'Round The Campfire > General Technical

Ever Drop Your Bike & Scratch Up The Engine Cases?


I have a Yamaha FJ1200 that is difficult to push around due to its size & weight. Both the previous owner & myself have dropped it onto its left side scratching up the engine case pretty badly. It's a real shame because the bike is a real cherry other than that. Here is a picture of the damage.

When the bike fell on me, the side stand had collapsed due to a weak spring. I have since replaced the spring & relieved the side stand stop so the side stand would extend forward a bit more instead of almost straight up & down. But the scratches really bothered me.

Today I decided to try to do something about the scratches & pulled out my sandpaper collection & some masking tape. I carefully masked around the side case & part of the belly pan to protect those areas. I then started with some 80 grit to remove enough material to remove the deep gouges & the pits. I used a criss cross pattern & dry sanded across the gauges instead of with them. I then switched to 320 grit (it was the only choice that I had readily available) & began sanding the remaining scratches out. This took some time & I experimented with both wet sanding & dry sanding. I couldn't really tell if one technique worked better than the other. I eventually swapped to 400 grit & started seeing a "grain" to the aluminum. I sanded with the grain until the previous scratches were gone & then switched to 600 grit. More of the same sanding & then I switched to 1500 grit to finish up with. These just happened to be the grits of paper that I had on hand. Once I was done with the 1500 grit paper, I used some McGuires Fine Cut rubbing compound/cleaner & rubbed that into the surface then buffed it out. It took me about 1.5 to a couple of hours total, but I think the results are well worth the effort. Have a look for yourself.

Good luck

Did a similar job on the clutch cover of my Ascot this summer.  When I bought the bike there was a rather large and deep gouge right across the middle of the cover.  I had been holding off on replacing the cover as I also suspected that the clutch basket was badly toothed and I was slowing gathering parts to completely replace the clutch.  In any case, I finally got around the putting on the new cover last summer.  The replacement cover was in reasonable shape, no scratches or gouges but the aluminum finish was looking pretty grim and there were lots of paint chips.  I sanded the aluminum finnish part clean and polished it up then masked it off and painted the rest of the cover with PJ1 case paint (after overall sanding of the cover).  It turned out reasonably nice except I made one mistake: I had stored the cover in my relatively cool garage so before painting it, I let it warm up in the sun for a while.  This actually made it a bit warmer than ideal so that when I painted, any over-spray immediately hardened so that some parts of the cover have a slight 'pebbly' look.  Not enough for me to do over at this point but I will probably re-do the next time I put a clutch in (which will hopefully be never).  The replacement cover looks much better than was was there originally.

PS: in the end, there was nothing wrong with my clutch basket (i put a new lower mileage one in anyway because I had it on hand at that point). The severe gabbiness I was experiencing with the original clutch was due to two things: thoroughly baked metal clutch plates which I replaced along with new fibers and the damping spring was missing (fortunately the low mileage used clutch that I purchased on EBay included the damping ring).  Doesn't say much for how a previous owner treated the bike.


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