HOW TO: Make your own Knee Dent Tank

I think if one was to be consious about how they hammer, a desired pattern could be reached resulting in no bondo. Im sure with a few hours more work I could get it pretty smooth, Im gona try the other side with a very wide faced round plastic mallet, if it comes out good ill post it up again!.... if not I'll cry like a little girl:thumbsup:
Great post!!! I'll be following this technique to upgrade/fix-a-dent in my old tank this winter! Now only if I could find a way to customize the seat myself, then my XS would truly be my personal frankenstein.
Hi Skillzman,

I just posted my intro in the Garage and this is my first post.

First off, hello. It's nice to talk to someone who gave me a ton of inspiration to buy an XS and even more to make it into the cafe racer I've always dreamed of having.

Secondly, I bought a 77 XS400D, which as you know, has the squared off tank. I want to have a tank that's a little more curvy (and maybe holds more gas), but it seems like finding another tank model that fits is pretty hard.

The mounting bracket on the tank you posted as an example of denting halfway seems to be close to what I have. What model is that tank off of?


Thats a stock XS 400 tank off an 81....mounting tab/bracket is about 3" rearward of a square style tank...just cut the old mount bracket off and relocate it or weld in a piece of flat stock in the correct spot...I went with a square style tank on my 81...essentially the reverse of what you want to do.
If I can get my hands on a few more tanks...I'm going to build to order a few this fall/winter.
LMK if I can help!,Matt

Thanks Skillzman!
Did either of you guys have any problems with the bondo breaking off around the emblem mount? I"m debating on grinding mine out but would like to avoid it, in fear of puncturing the tank.


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I did not have any body filler pop, and even when I laid the bike down at 90mph it still did not pop, even though the tank dented close by. There are many factors that will go into body filler poping around the applied surface. You should take precautions during preparing the tank and scuff up any surface needing filler with 80 grit. It looks like you are using Bondo, which can be also help to crack due to a lack of quality.

I decided to use Evercoat over any Bondo product a long time ago. While I using Bondo I would go through tons of sand paper, and when I switched over to Evercoat I use 2 pieces of sand paper for an entire tank. I used Evercoat Rage for my tank because none of my low spots were over an 1/8". If there will be more than an 1/8th to be filled I would use some kind of body filler mixed with a fiber 'rebar'.

My recomendation is to go ahead and finish the tank as best you can. If you forgot to scuff up the surface before filler you might want to get the bondo off with wire wheel, scuffing with 80 grit, and refilling it all with Evercoat Rage. On the other hand, if you have already scuffed it up before applying Bondo, just go ahead with that process and see how it works for you. It's all a learning process...:thumbsup:
DANG!!!!!! Well you live and learn. I'm gonna finish this tank in bondo and when it falls apart I'll redo it with Evercoat. Hell, makes for more home brew drinking, right? I have a new born so its not like I have friends or a social life. My garage is my social life.

Thanks for the tips guys
Can't thank you enough for the painstaking tutorial. Start to finish it has now allowed me to realize that with patience, and diligence, I could do this. And trust me I have no experience. None other than knowing that what the mind can perceive it can achieve!
G'day Skillsman. I am from South Australia and have just bought a wreck XS400. The tank has a big dent so I was considering knee dents, but not sure if I'm game. I am an old biker from wayback, use to have a couple of Trumpys and a Matchless. Had kids and sold all my toys up.
Good post, Goodonya, Terry