1980 SR250 Build, get Excited

Got some time in the garage during the week and some this weekend.

Stripped the rest of the paint off the rear end


Cut the old shock mounts from the old shock towers and cleaned them up



Laid some beads down on the frame rails and supports, not the prettiest welds but they should be very strong



Cut out the front frame rail braces


Mocked up and started cutting out metal for the new shock mounts



Mid cut I got tired of bending over on my HF 4x6 bandsaw to cut my metal, so I decided to finally make it into a bench top model






I still need to mount the motor for the saw, then back to motorcycle fab business. She'll be standing on her own again soon. :)
 
All work and no updates makes for a boring build thread ;D

So about that gas tank... Saw this one day and liked how it looked, and it was decently priced so I gave it a go


So it didnt line up with the old mounts at all, no big surprise, so I had to get rid of them





And this is how I mounted the new tank: got some dowel rod that the mounts fit on, cut that to the correct size and then copied that to some steel rod, made some mounts to hang where needed and well, the pictures explain

Old vs New


Dowel cut to length



Perfect fit


Transfer to some rod


Brackets and the rod cut


Tacked in place, getting these to stay in place with the tank on so I could tack them was a PITA


Plenty of space down the tunnel, angle makes it look like that tab is close but it's just the angle of my phone, plus it most likely wont stay there


Rear mount, cut some 7/8 tube to the height I wanted it to sit, welded a nut to the back of a washer, welded the washer with the nut facing in to the piece of tube, then I welded the tube to that flat going across the frame. I used the old gas tank mounts for rubber mounts, I drilled them out to the right bolt size and then cut and trimmed one to make a rubber washer for the top bit, and the other I just slid over the piece of tube.



So if you're observant you may have noticed that the swingarm is different. Yeah, thats right, mono shock swingarm from an XT250, bolts right on. I got the shock for around $60 IIRC, its from China and its for a pit bike, 1200lbs spring, all I really care about was getting a shock at the length I needed so I could make the mounts, if it craps out on me I can always cough up for a real mono. I also welded up the front sub frame braces.


Made side mounts that hug the frame rails, and she is standing on her own feet again 8) that shock is pretty stiff



Brace for the underside of the shock mount tacked up, drilled 1/2" holes in a pattern to relieve some weight


Got the rear hoop cut and attached, and yes there are frame slugs in there, I cut slots into the top of the frame and hoop so I could lay a bead down along the entire slug, and then around the tubes


Next step...




Now I just need some foam and wax... to be continued
 
Looking good! FWIW, instead of a slit for the slug, you can just drill a 3/8 hole in both frame and hoop, on 2 sides and plug weld.


Sent from my iPhone using Tapatalk
 
Some welds fer ya


Fully welded shock mounts, rear gas tank mount, and i decided to complete that subframe brace weld



Front gas tank mount welds



Re-welded the backbone, it was pretty weak looking
 
Seat update

Glued the blocks up


Rough shape


Refining


Didn't like how this was turning out for a few reasons:
#1 hot glue is not a good idea to use, it doesnt sand or file easily
#2 i put a cardboard spine in the middle which ended up just getting in the way
#3 I tried using plaster to fill some holes, ended up being a disaster
So I put it in the trash! haha


Take #2








It's taped up in multiple layers everywhere, I guess all that taping hockey sticks for 13 years really paid off :p
All ready for some glassing 8) If this works out nicely I may consider making a simple video explaining the steps in detail, there aren't many out there and the ones that exist are sort of vague
 
The blue painters tape will be stuck to the inside of your glassed seat. You may want to put some wax or packaging tape or something over the blue tape that the resin won't stick to. It will be a pain to remove once the resin cures.

Looking good.
 
Here's how I spent part of my weekend

Laying down some cloth



A few hours later I was able to cut it with a brand new razor blade




Trimmed it to the mold's edge, foam popped out easily and so did most of the tape, some got a little resin on it but it pulled off with some patience




Now I'm going to sand the inside a bit and apply a few more layers of glass to beef it up, it's a little flimsy, then I'll get it a big final sand and apply a few layers of gelcoat to seal it up. I think it turned out pretty well for my first ever attempt at fiberglassing.
 
That seat looks great so far! ;D Can't wait to see what it looks like once you've got it upholstered and secured to the frame. I've been thinking about doing fiber-glassing for my seat for my CM400, but it just seems like a lot of work...
 
I agree - very good job for 1st time. I assume you will also construct a separate seat pan (or platform) to pad and upholster that will attach to the seat. I also assume you will be trimming the front of the seat so that it exactly meets the rear arch of the tank (where the tank mounts to the frame) and not have so much overlap. Or maybe I just need to wait and see ;D.
 
Thanks for the responses guys.

I will be constructing a separate seat cushion that will attach to the fiberglass seat pan, it will be made of plastic PVC sheet 1/8" thick, Ill be using a heat gun to form it, not sure if it will cover the front hump as well, then I will be gluing multiple layers of seat foam and taking it to an upholster to get it stitched and stapled.

For the front of the seat pan I dont think I'll be trimming it down since it wraps around the front and has a hole cut out for the rear gas tank tab, It's a little step-staggered but I should be able to get it closer to the tank than when I was mocking it because the plastic bubble wrap wont get in the way, not really sure at this point, I have to spend some time staring at it.

Anyone have advice for mounting this seat pan, should I fiberglass tabs into the seat pan for mounting to the frame, or should I drill holes in the seat pan?

More to come soon, I have the pieces of fiberglass cut out so I can beef it up from the inside, maybe even adding some bracing.
 
do you have a link to that tank? I am trying to salvage mine but i'm leaning towards buying a new one. also sick build man !!! thanks Hayden
 
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