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Sebspeed's 750 Slingshot

30K views 209 replies 20 participants last post by  SEBSPEED 
#1 ·
I've always wanted to build a slingshot... now I get to build 2!!

This one is a 1990 750. When I got it, it had already had 07 gixxer front and rear ends grafted on. The front looks legit and the rear is not bad, but incomplete.

Once I get the chain line straight and the rear wheel centered, I'll move on to fitting an R6 tail and an MT03 headlight.

The motor is going to be mostly stock, I'm adding k&n pods and a sidewinder header. Can tbd.

Also adding some modern controls, lots of braided hoses with fancy fittings, Koso speedo, and a paint job.

While I'm taking breaks from all of that, I'll be scrubbing the frame and swingarm with Scotch Brite to give them a nice satin brushed finish.

This is how I got it:


Paper proof of start date:




Sprockets a bit off



More tomorrow...
 
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#6 ·
In order to straighten out the rear end, I started by getting the sprockets in line. To do that, I had to flush up the inside right frame rail.





Nicey nice



Chain is now straight



Time to find out where the wheel is



Nothing a 3/8" offset sprocket can't fix



Probably going to use this one

 
#8 ·
PBI 3/8" offset 15t front sprocket ordered today, as well as a 45t steel Vortex rear.

Turned up an AL spacer to fit where the link for the 07 swingarm used to. Tuned the length of the adjustable links.

Next step is to cut the right side swingarm spacer, but need the rear sprocket first.

Then jack the ride height up to where it should be, then it can come off the lift and start fitting the subframe.
 
#10 ·
Only got a little in on this today, was in the paint booth working on CB900 case covers.

Got back and turned up the right side swingarm spacer.



While I was hunched over the lathe I cleaned up a spare 22mm socket to prep for milling teeth later, will be the tool to tighten the swingarm nut.



Sprockets arrived, fitted front



Need to trim the inside of the left frame rail to fit the arm, then mark out the frame for trim to fit chain run top and bottom.

Rear sprocket will be flipped so the relieved side fits against the wheel, this brings the chain .140" closer to the wheel/tire.

 
#12 ·
Hate to say it, but I got caught up in other things, only done a quick mockup of the tail.

The seat will be a ton of work.





 
#17 ·
Re: Sebspeed's 750 Slingshot discussion

you still can, just make new bolt holes :)
best answer ever!
agreed though the seat unit looks great and 4" shorter will look even greaterererer
 
#18 ·
Finally got some hours in today. Removed 3" total from the subframe. 2" wasn't enough*.



Will make for a nice transition line in the bodywork









Makes seat work easier



Template for mounts



Looks good, transfer to aluminum



Fleshed out





That's a sexy mount!










* that's what Yan said :oops:
 
#19 ·
In order to weld them on, I needed to figure out a way to hold each mount at the same height. I prefer fixturing vs working off dimensions and scribe lines. Fixturing always seems to turn out better.

Easiest thing to go off of was the rear set mount hole... but I didn't want to waste time cutting and drilling a temporary structure... the closest handy item did the trick



All I had to do was cut a taper in a bolt head to center it up, and add a piece of drop to the jaws to set the height.







Worked out well









Top mounts next
 
#23 ·
Right, let's get this subbie mounted, I want to sit on it!

I cut some scraps of cardboard till I was happy, then rendered the top mounts in aluminum.



Not bad for non-cnc equipment if I do say so myself





In situ



Tacked



Before I tacked the mounts, I drilled and tapped them for M6x1 bolts.

Once they were glued in place, I transferred the bolt hole location to the subframe rail.



I had to dress up the subframe rails a little to make room for the bolt heads





And all back together...

 
#81 ·
Re: Sebspeed's 750 Slingshot discussion

I hope I'm in the right slingshot discussion... :D

Those subframe mounts you made look great. Really nice work, man. But are you sure one M6 bolt is enough to do the trick? Looks like you have plenty of meat for two M8's on each upper mount. Just a thought. :)
Oh, so you were planning to weld them on eventually. I see now. Six months later. Good to know
 
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