So you just cut the front end of a sport tank off, then cut the rear section out for the tail light.
Yes. The bottom of the tank was removed as well.
So what was the process to make the seat fit with the tail section. I see you cut the seat in half, then how did you make a section to mesh with the cowl?
OK, first I chopped the back of the frame a bit. You can see in the pic from underneath that the back of the top frame rails where the rear of the stock seat would be have been cut on an angle so they come up and meet with the tail section platform nicely. The curved rear fender support was cut off and replaced with a flat support.
Then I basically took a piece of sheet metal and welded it to the top of the back section of the frame. This is the platform the tail section would sit on. Actually the tail now slips over the platform a touch but that comes later. To start with the platform was longer and wider than needed.
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Then I cut the seat pan where I wanted & welded a vertical piece of sheet metal to that back of it to support the bum stop portion of the seat. Again it was bigger than needed originally.
Then I mounted the seat pan on the bike and placed a piece of 1/8" steel directly behind the vertical portion of the seat pan and taped it in place. This served as a temporary spacer that I could make the tail section match up to. I needed a bit of a gap to allow for the seat upholstery.
Then just cut, grind, and file the front of the tank (tail section) until it sits flush on the supporting platform and meets up nicely with the 1/8" temporary steel spacer.
If you look at the pic with the seat hinged open you can see I put a bit of a front on the tail section. It’s about 1” all the way around. That made it easier to have a nice straight edge on the front of the piece. Even if my filing and grinding wasn’t a perfect match to the 1/8” spacer, once I welded the front plate on all was well.
Then trim the sheet metal platform so the tail section just slips over top so you don’t see the edge of the platform when the tail is mounted.
Then I drilled the 4 holes in the platform for mounting bolts and welded in mounting tabs on the inside of the tail section.
Once the tail is bolted in place, remove the temporary 1/8” space and grind the support for the seat bum stop until it matches the front of the tail section.
There, I hope that makes some sense. Sorry, I don’t have digital pics of the process.