XS400 Tracker/Brat Build with Frame Modification


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Hi everybody, first post on the forum so bear with me if I make any mistakes here. Also, sorry about the length, this got way longer than I expected.

Link to imgur gallery here: http://imgur.com/a/8ev4B

At this point, I'm done with what I would consider 'Stage 1' of the modifications to the bike. This means the cosmetic parts have been replaced and the frame has been modified. I'm currently trying to troubleshoot some minor electrical issues (headlight, blinkers and starter motor), but other than that, it's back in one piece... for now...

I'll stick a preview up here, but read on to see the full progress of the build.


About a month ago I bought my first bike: 1981 XS400 Special.


I didn't know anything about bikes and didn't even have my endorsement to take it for a test ride, but the seller cold started it easily and it ran smoothly, so I took a leap and bought it. I rode it every nice day for around 2-3 weeks and loved every second of it.

I have a friend (lets call him K) who has a lot of experience around cars and bikes (built 2 R6's and a couple dirt bikes, heavy performance mods to his car, etc.). From the get-go, he was sending me pictures of ideas for customization.
K sent me a picture of a Tracker build for an XS400 which I thought was bitchin'. We decided to base the build off this.


Once I got that inspiration, I went home and started stripping stuff off.
After an hour, I sent K a pic of my "progress".


He wasn't impressed so he came over the next day and we tore more off.



At this point, I still wasn't committed to frame modifications. I haven't done anything like this before, and the concept of cutting the frame on my perfectly functional ride scared the shit out of me.

Regardless, I ordered some new bars, signals, mirrors, headlight and grips and got them installed. It was starting to look a little cooler.


Eventually K won me over and I ordered a seat hoop and custom seat from Dime City, and committed to cutting up my baby.

The seat arrived last Wednesday, and as soon as work was over Friday, I rode it over to his house to start the major fabrication.

We started by cutting the rear seat support off so we could get an idea of how the new seat would look sitting on the frame, and we immediately noticed a problem. The 'Yamaha hips' the bike has were sticking way out past the sides of the narrow seat. (I wish I had a picture of the way it lined up originally, but picture about 1" of air on either side between the seat and the frame, not cool.

I had seen a build where someone bent their frame in, in order to reduce the flair out. I brought this up to K and his roommates C and J (both also very experienced in car modification and who knows what else) and we debated the merits over a couple beers, and eventually decided "Fuck it" and went for it.

We cut the forward cross-support and bent one side down out of the way. Then we pulled out the heavy clamp.



Once we cut the support, it was surprisingly easy to bend. We would take it in past where it needed to go, then let the tension out of the clamp and measure it against the seat hoop I had bought. It took maybe 5 iterations of this process, each time moving them 1/4" or so closer together.

We used a piece of wood in the front to help the sides bend evenly and to control where the bend happened. The two sides moved remarkably symmetrically, and only took a small amount of adjustment after the clamp job.

Once we had the alignment where we wanted it, we got to cutting off all the mounting tabs for the stuff I no longer needed. Here is K doing some of the cutting.


Finally we measured where we wanted to weld the hoop on and I got my first experience using an angle grinder cutting the back of my frame off. A little nerve-wracking, but fun.

We had decided early on that we also wanted to cut the seat down from 24" to about 21". The seat was made of an aluminum pan with foam, leather and felt glued to it. It wasn't hard to pull all of that back and make the cut. Here is the bike with the cut frame and seat.


Now it was time to bring out the welding torch. We had picked up a couple gauges of steel (thicker for structural parts, thinner for the battery box, seat pan, etc.) and the seat hoop which came pre-bent. C is a self-taught welder who did a totally fantastic job, he also works for beer and small bills, which fit my budget nicely.


The first welds we did were the seat hoop, re-welding the forward support, and fabricating a rear support from our thicker steel. K jumped up and down on the tail to test the welds, comments were made about the land-whales I’ll be able to bring on the back… thanks guys…

We test fitted the seat and everything seemed to fit nicely. This was the first good look I got at how the bike would look when all was said and done.


At this point stuff started to move rather quickly, we cut the rear fender down and fabricated a seat pan. As it was around 10PM Friday night and we are all in varying stages of our 20s, we were all drinking throughout. K and I were sipping beers in the garage while C, J and their roommate S were taking shots in the kitchen. When we called C out to weld he was certainly drunk.

As you can imagine, I was a little apprehensive about letting our drunk welder touch my baby, but I let him do his thing and he did a damn good job. I stopped doubting him at this point.


Unfortunately, at this point we realized that, while we had gotten rid of a majority of the bikes ‘hips’, they were still there more than we wanted. We had to make the frame cuts a little behind the shock stays, so it flared back in slightly before the junction with the seat hoop.

K came up with the idea of making brackets which would cover that dip, and make a clean, blended line to the back of the bike. You can see the plates below clamped in place before welding.


When we called C out to weld this time, he was pretty much plastered. He nearly fell backwards over the welding cart when he came out. Nevertheless, as soon as the mask was down, it was all game-face. Color me impressed.


Here you can see the detail of that part after a little grinding. We pretty much left it here for the night. It was past midnight, and we were all drunk and tired.


We had also fabricated a battery pan at some point during the night, here it is sitting in place. We waited until the next day to weld it in.


It was time to finish the welding. We fabricated a small wire hanger to weld down below the seat pan, as well as… something cooler…

Here is C welding that “something”


Okay, I won’t keep you waiting… We welded a bottle opener under the seat. It’s exactly as awesome as you’d expect.


Now I don’t want you to be getting the wrong idea here, drinking and riding is downright idiotic. Don’t do it.

Now, that being said, I cried tears of joy when I saw how awesome this was. This is my favorite part of the build, and I’ll be walking out to the garage to crack my beers for the next couple months.

Do you remember those gaps between the seat and the frame I was complaining about earlier? Well they were still there, just much less pronounced. Our now hungover welder C added the triangles to get rid of the gaps.


And here is a view of the whole rear end, pretty much completed. The matte paint we were using originally looked dumb and didn’t match the rest of the frame, so we switched to a satin instead.


I had gotten a 4 cell antigravity battery (also from Dime City). It was so much smaller and lighter than my old one, I couldn’t believe it would be able to run the bike.


Here it is installed in the box with the rat’s nest of wires.


We put some rivnuts in the aluminum base of the seat and fabricated a bracket to pin it under the tank. Once we got the seat attached, the major fab work was done.
Here is the completed result.



K has used the tagline ‘Close-Enough Engineering’ on some of his other projects that were not necessarily though out fully, where ‘close enough’ was the standard they were held to. I though this bike really embodied that spirit, and somewhere along the line, we decided to call this bike the ‘Close-Enough Special’. Eventually we’ll make a logo for the tank. Here is what I came up with as an idea.


K is much better at graphic design than I am (talented dude, right?), so we’ll see what it winds up looking like in the end, but this is the basic idea.

(post was too long, cont. in comments)
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I still have a ton I want to do to it. Painting the rims, getting more knobbly tires, custom downturned exhausts, smaller levers, longer rear shocks, some sort of front fender, a better paint job and a full re-wire are all in the future for this guy, but for now I just want to get it back out on the road.

Like I said at the beginning, I’m still having some electrical issues.
I can’t get the headlight to work, the starter hasn’t worked since we first started taking things off (except for yesterday when it would go without the button being pressed???) and the blinkers don’t actually blink. I’m not opposed to using the kick start for the time being, and I’m hoping to have the rest of the electrics sorted this week, so I can take it for a long ride.

All in all, things went ridiculously smoothly, especially considering nobody involved had ever attempted anything like this. We certainly didn’t realize everything we’d need to do at first, but we were able to roll with the punches and I’m very happy about how it came out. There’s not much I’d want to do differently if I was to do it again.
I really can’t thank K enough for taking this modification to heart, as well as C, our drunk and talented welder. I never would have even dreamed this was possible for me to do, but K saw the potential and they both helped me enormously with the actual modification.

Questions, comments and criticism are all welcome. I’ll be updating this thread as I do more, but posts may be few and far between.
Thanks for reading and ride on :).

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love the idea bottle opener under the seat :)

that is a great build and lots of thinking/working went into getting it right :thumbsup: to you guy's
This is a great-looking build; I might have to borrow the idea of narrowing the existing brace when I get to the point of modifying my seatpan.
welcome! looks like a sweet bike already :)

About your electrical issues. The blinkers that don't blink are probably caused by the replacement of high power-drawing, old-fashioned light bulbs in the indicators by the new, either halogen or LED bulbs in your new blinkers. The stock flasher relay needs a certain load to be triggered and the new bulbs don't draw that much power. Two options:

the right way: replace your relay with a LED flasher relay. This often requires you to attach an extra ground wire to the new relay (did this myself)
the wrong way: add resistors to your blinkers to increase their power draw.

as for the start button, you probably have a grounding issue due to the new bars. A lot of the switches ground through the bars to the frame, if your bars are painted they will disconnect these grounds.
The ground for the bars come from the left switch housing. So the paint under both sides must be removed.
Willem, thanks a ton!!

We got the starter working today and I've got a relay on-order!
We also got the headlight working as well, but that was a different issue.

One last thing, since the build was started, the neutral light has stayed on constantly.
Any thoughts as to why?
cool, good to hear it worked out :thumbsup:

don't know where the neutral sensor itself is located actually, but my guess would be that that's off in some way. But I am by no means an electrical engineer like some other guys here..
Yeah exactly. We cut it to the shape of the new hoop and welded it straight on. Pretty much what you see is all there is, since the seat pan and battery box keep everything else clean.
Was that 4cell antigravity actually work with electric start? I know it's only about 120 cca? Thought 190 or so was the minimum
jdizon, I was surprised when I first tried, but it works quite well.
At full charge I could probably crank it for at least 30 seconds before it runs down, maybe up to a minute.
jdizon, I was surprised when I first tried, but it works quite well.
At full charge I could probably crank it for at least 30 seconds before it runs down, maybe up to a minute.

Nice! I'll get the 4 cell instead of the 8 cell if it'll work with the electric starter. Thanks for the info!
What size is your rear tire? Im wondering because i want to basically do the same thing as you guys, all i want to do differently is make it a bit slimmer, or is that even possible? Do the springs hit the tire? Also, when you were bending the frame in, did you worry about bending the springs at all?