Late Model (lift off) Seat Mod and Rebuild

rhkansas

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Part one: Getting to the Bottom of Things..
Please note that this modification is for the late model (1980) and later special and special 2 models with the lift off saddle. I'm also not the greatest at documenting projects as I go along - tend to get involved in the work and forget all about the camera on the workbench - I apologize in advance for any lacking detail in the accompanying photos.
This modification will lower the seating position, and requires sheet metal cutting, forming and welding - but nothing too complicated. There is also some considerable foam work - still nothing terribly complicated. The end result will be a saddle much more comfortable than the stock configuration with support in the right places.
The first order of business is to correct the issue in the foundation of the seat pan itself. The stock pan has a glaring issue in its construction that makes for an uncomfortable seat as the foam is compressed and you're left sitting on some very uncomfortable pressure points. Here's the starting point - Seat in need of rebuild - cover torn and foam beginning to break down.
A-DSCN1056.JPG


Carefully bend out the holding teeth and remove the cover - bend them only enough to get the old cover out from under - I have had most success at bending no more that 45 degrees or so...
C-DSCN1058.JPG


Remove the seat cover and the old foam. Try to remove the foam in one piece, particularly the pillion portion, as it will be re-used. The bare pan now exposes the problem area that needs to be addressed.
E-DSCN1064.JPG

Note the raised center part - this is what you're sitting on when the foam compresses - about 6 inches wide and slanted forward - it will make your backside sore in a short time.

F-DSCN1065.JPG

The next order of business is to mark the perimeter of this raised section - being sure to retain the holes for the rubber bottom bumpers and cut it out. I used a dremel with the reinforced cutting wheels - expect to go through 4 to 6 of them by the time you're done. It will look like this:
G-DSCN1067.JPG

I used a grinding wheel in the dremel to smooth out the ragged edges a bit.

Next, make a cardboard template for a new bit of sheet to cover the hole. The top edge of the back should be level with the top surfaces of the seat mount latch towers on each side. Here's my template:
H-P1010004.JPG


Cut this out of 16 gauge sheet, and then form to sit in the curved profile of the pan - it should sit flat on the pan without rocking or having to be forced into place. When satisfied with the fit, weld it in place.

J-DSCN1074.JPG
Welded on the top - note the upper back edge alignment with the top of the latch towers.

I-DSCN1073.JPG
Welded the bottom. Drill the rubber bumper holes through the new sheet metal overlay.
Of the three seats I have done so far, only one has had the factory vinyl edge protector somewhat intact. NONE have had an intact edge protector at the lower skirt corner where it's needed most. Unable to come up with any suitable replacement, I worked the bottom edges with a file and emery paper so there were no sharp edges over which the cover will be stretched. After all this is done, clean, sand, prep and paint the pan - when the paint has cured, it will be time to move on to building up the foam.

Coming up...Part 2 Fun with Foam
 
Interesting mod. I look forward to seeing how it turns out.
Regarding bending those tabs.... They "work harden" pretty quickly. I've had good luck taking a torch (could even use your TIG welder) and heating them cherry red and air cooling slowly. That anneals them soft again and they can be bent easily without breaking. There's also the added benefit of burning off the rust on and around them. Be careful though... pretty thin sheet. Don't melt them off. :)
 
Part 2 - Fun with Foam - Building a Foam Foundation.
OK - all the metalwork's done, paint has cured, and we're ready to start building the foundation that will provide the support under the cushioning foam. For this saddle, I used 3 types of foam (and the old pillion block). The foundation layer is made up of mid-weight polyethylene closed cell foam - 1/2 inch thick. The cushioning foam is 2 inch thick re-bond, and the outer smoothing layer is 1/2 inch thick luxury hi-quality open cell polyfoam. I sourced the closed cell from a local surplus supply - they had several rolls of the stuff - really cheap. The re-bond and open cell were sourced online from the Foam Factory - the closed cell can be obtained there also. Adhesive used is 3M #74 Foam-fast spray adhesive. I found gluing the closed cell to be a bit of a challenge - the polyethylene required a bit more open time to allow the adhesive solvents to penetrate - sometimes requiring a spray - apply - pull off - re-spray, and apply again, but once it sticks, it's STUCK! Foam working tools include small medium grit sanding drum suitable for a VSR drill, an electric carving knife, a good sharp scissor / shear, and a long straight blade utility knife. I used a Stanley snap-off blade type - fully extending the blade gives you a nice long, very sharp carving instrument.
K-P1010001.JPG
The next order of business is to create some patterns for the support panels - side of pan, top of pan (seat area), back support, and nose filler. Here are my patterns for the top of pan (top) and sides (bottom)
N-P1010003.JPG

and for the back support and nose filler..
O-P1010005.JPG


These patterns are now cut out of the 1/2 inch closed cell foam - 2 each of the side and top patterns - 1 each of the back support and nose filler. While we're cutting foam, cut off the pillion block from the original seat foam, and the two side pieces that fill in the drop off in the pan just above the lowermost skirt point...these are the bits needed....
L-P1010006.JPG

and the pillion block cut off right behind the main seat cushion.
M-P1010007.JPG


Glue the side pieces back in place and trim so they do not cover any of the vertical side of the pan just below. Their purpose is to simply fill in the void of this shoulder drop-off in the pan and provide a full vertical surface for the closed cell side panel to adhere to. Then, glue the pillion block back into place and trim to remove any of the thin layer that may cover the pan sides and flange, and trim the front to achieve a slight back angle that continues the curve of the new pan form. The tool of choice for this work is the electric carving knife.
Now, we can begin to glue the closed cell pieces to the pan - starting with the sides. Align the bottom edge of the side piece with the bottom edge of the pan - once adhered firmly - trim the upper edge as needed to be even with the surface of the pan. Before gluing the top pieces to the pan, bevel the inside edges (the semi-circular part) by marking a line about 1 1/4 inches from the edge, and using the utility knife, cut at a bevel to the line - leaving about a 1/8 inch margin at the bottom edge of the piece. Glue the top pieces in place, aligning with the outside edges of the side pieces and the front edge to the front kick-up in the pan. Finally, determine the desired height of the back support and trim the bottom edge as needed - leaving a tongue to fit between the bottom
pieces (the back support on this saddle has a 1/2 inch margin above the top of the pillion surface - bevel the tongue before gluing. The final objective is this:
P-DSCN1633.JPG

Now, all the outside beveling can be easily accomplished using the utility knife. The final effect is to create a shallow bowl with a rounded drop off to the side just in front of the seat area. The lower edge of the sides is beveled about 3/4 inch up from the edge - the lower edge beveled down to the metal of the pan.
Q-DSCN1635.JPG

Here you can see the line that continues the back angle down to the bottom of the skirt. The side panel will be trimmed away nearly down to metal just behind this line. The foam foundation is done...next up - part 3 - Puttin' the Cush On.
 
Very interesting that high spot in the middle! I always thought the Special seats would be very comfortable until I sat on one for longer than 30 minutes. What annoyed me most was that they lacked any backwards adjustment so tend to keep you close to the tank. But they look nice. When I had a 1B with a standard shaped seat I could just sit a little farther back.

I shall follow this with interest....................
 
Oh, I just remembered something I read on a toilet wall when I was about 10 years old:

"The thing I hate about contour chairs is my contours don't fit theirs"

I should have paid more attention...............
 
80SG Special seat is a one off styled clip on seat although the pan is the same as the later 81-83 seat. These 80SG seats are more comfortable due to the movement allowed because of the seat styling. 81 and later style foam and covering restrict any forward/backward movement and this causes adds to the discomfort on a long ride.
 
Part 3 - Puttin' the Cush On. OK pan's modified, foundation's finished - time to make this look like a motorcycle saddle. By now, you should have a good custom upholsterer selected - one who has experience with motorcycle saddles, and is willing to talk over the look you will want for the finished product. It took me several tries to find one - lots of them who have experience, but not that willing to go over specifics, and you'll get what they decide to produce. Find one that will discuss all the details - seam placement, seam type, welt placement, etc. This mod is a lot of work - might as well get the best final result you can. Now, back to finishing out the foam work...
Measure across the seat at the widest part - cut the re-bond 2 inches wider than this measurement - measure the seat from the front edge of the pan to the top edge of the back foundation support piece - cut the re-bond 3 inches longer than this measurement. Place this on the seat - centered and allow 1 inch of foam to overhang the pan in front - measure from each side. While holding in place, roll back the foam from the back of the seat and hold it - spray the back of the seat and the corresponding area of the foam with adhesive and, after 30 seconds or so of open time, roll the cushion into place - it should stick immediately. Now, roll the front portion back and repeat the procedure. It looks like this:
S-DSCN1638.JPG

After it's glued and set, trim the sides and back using the electric carving knife. Watch the angle of cut closely at the top edge of the back - the front face of the cushion should be higher than the back. Do not trim anything off the front of the cushion - the overhang off the front of the pan is needed to fill the gap between the pan and tank. After trimming to this basic block, mark the desired profiles on the front and sides of the cushion.
T-DSCN1641.JPG

Side profile marked - mark on both sides as symmetrically as possible.
U-DSCN1639.JPG


Now begin carving using the electric carving knife - carve in thin layers, working toward the final desired profile. I find it easiest to carve the forward profiles first and then address the seat bowl. Forward area carving in process:
V-DSCN1640.JPG


When carving the seat bowl, work from one side and then the other - the knife is not long enough to reach all the way across - it will go about halfway. Carving in thin layers allows you to see the position of the blade tip under the foam. The objective here is to have a 1 inch layer of re-bond cushion in the bottom of the bowl.......yes, that's all it takes! Here's a layer being taken out:
X-DSCN1644.JPG

Kind of hard to see, but here's the final profile in the seat bowl:
Y-DSCN1645.JPG

Here's the rough-carved seat set on the bike - no mounting hardware on the seat so it's sitting a little askew, but it gives an idea of what it looks like at this point:
Z-DSCN1647.JPG

Finish fine carving / smoothing with the sanding drum in a drill. Re-bond does not sand well, so this needs to be considered only a refinement step - all major carving has to be done with the electric knife. Drill / sanding drum does very well in smoothing off ridges and bumps that did not cut cleanly.

Finally, cover the entire seat with a layer of 1/2 inch thick luxury HQ open cell foam (smoothing layer & initial cushion).
ZZ-DSCN1648.JPG
The mark on the foam above is the edge of the back support. Cut the sides of the smoothing layer along this line to where it begins to curve over the top - glue the top portion down, then smooth the sides - cut out (dart) as necessary and glue down. At the front, cut the covering foam even with the end of the re-bond and glue in place - then cap with a piece of open cell and trim to match the contour. Use the sanding drum to bevel the edges of the smoothing layer along the sides and back of the seat. Now it's time to pay a visit to that upholsterer.
Here's how this one turned out:
ZZZZ-DSCN1659.JPG

ZZZZZ-DSCN1660.JPG

ZZZZZZ-DSCN2271.JPG
 
80SG Special seat is a one off styled clip on seat although the pan is the same as the later 81-83 seat. These 80SG seats are more comfortable due to the movement allowed because of the seat styling. 81 and later style foam and covering restrict any forward/backward movement and this causes adds to the discomfort on a long ride.
Yes, the '80 did not have the severe kick up in the cushion in front of the pillion.
 
Great write up. Beautiful seat! Um you should let me ride that, for testing purposes only of course. I usually ride a 79 standard seat which has a slight step. Last fall I took Allison's special out for a 100 miles and spent quite bit of time back on the passenger pillion. But that's how it goes with a 36" inseam on a smallish bike.
 
Great write up. Id Beautiful seat! Um you should let me ride that, for testing purposes only of course. I usually ride a 79 standard seat which has a slight step. Last fall I took Allison's special out for a 100 miles and spent quite bit of time back on the passenger pillion. But that's how it goes with a 36" inseam on a smallish bike.
It does lower the seat a bit...but...I have cruise pegs - lets you stretch out a bit once underway. If you plan on being in Arkansas again this April - I'll be happy to let you take it for a little spin.
 
Lovely seat with a subtle modern feel about it, well done!!! I have just checked my SH (US Model) and it does not have the ridge up the middle that you cut out. So basically it just lacks that forward/backwards adjustment. I think I will attempt to make a standard type seat using your techniques
 
Part 3 - Puttin' the Cush On. OK pan's modified, foundation's finished - time to make this look like a motorcycle saddle. By now, you should have a good custom upholsterer selected - one who has experience with motorcycle saddles, and is willing to talk over the look you will want for the finished product. It took me several tries to find one - lots of them who have experience, but not that willing to go over specifics, and you'll get what they decide to produce. Find one that will discuss all the details - seam placement, seam type, welt placement, etc. This mod is a lot of work - might as well get the best final result you can. Now, back to finishing out the foam work...
Measure across the seat at the widest part - cut the re-bond 2 inches wider than this measurement - measure the seat from the front edge of the pan to the top edge of the back foundation support piece - cut the re-bond 3 inches longer than this measurement. Place this on the seat - centered and allow 1 inch of foam to overhang the pan in front - measure from each side. While holding in place, roll back the foam from the back of the seat and hold it - spray the back of the seat and the corresponding area of the foam with adhesive and, after 30 seconds or so of open time, roll the cushion into place - it should stick immediately. Now, roll the front portion back and repeat the procedure. It looks like this:
View attachment 111364
After it's glued and set, trim the sides and back using the electric carving knife. Watch the angle of cut closely at the top edge of the back - the front face of the cushion should be higher than the back. Do not trim anything off the front of the cushion - the overhang off the front of the pan is needed to fill the gap between the pan and tank. After trimming to this basic block, mark the desired profiles on the front and sides of the cushion.
View attachment 111365
Side profile marked - mark on both sides as symmetrically as possible.
View attachment 111366

Now begin carving using the electric carving knife - carve in thin layers, working toward the final desired profile. I find it easiest to carve the forward profiles first and then address the seat bowl. Forward area carving in process:
View attachment 111367

When carving the seat bowl, work from one side and then the other - the knife is not long enough to reach all the way across - it will go about halfway. Carving in thin layers allows you to see the position of the blade tip under the foam. The objective here is to have a 1 inch layer of re-bond cushion in the bottom of the bowl.......yes, that's all it takes! Here's a layer being taken out:
View attachment 111368
Kind of hard to see, but here's the final profile in the seat bowl:
View attachment 111369
Here's the rough-carved seat set on the bike - no mounting hardware on the seat so it's sitting a little askew, but it gives an idea of what it looks like at this point:
View attachment 111370
Finish fine carving / smoothing with the sanding drum in a drill. Re-bond does not sand well, so this needs to be considered only a refinement step - all major carving has to be done with the electric knife. Drill / sanding drum does very well in smoothing off ridges and bumps that did not cut cleanly.

Finally, cover the entire seat with a layer of 1/2 inch thick luxury HQ open cell foam (smoothing layer & initial cushion).
View attachment 111371 The mark on the foam above is the edge of the back support. Cut the sides of the smoothing layer along this line to where it begins to curve over the top - glue the top portion down, then smooth the sides - cut out (dart) as necessary and glue down. At the front, cut the covering foam even with the end of the re-bond and glue in place - then cap with a piece of open cell and trim to match the contour. Use the sanding drum to bevel the edges of the smoothing layer along the sides and back of the seat. Now it's time to pay a visit to that upholsterer.
Here's how this one turned out:View attachment 111376
View attachment 111377
View attachment 111378
Very awsome
 
Really nice write-up RHK!

Can you tell us how you did the Yamaha tuning fork logo?

Pete
Thank you!
I printed the image from google images - took it along to my upholsterer. The person who does their custom embroidery has a set up that scans the image and does the embroidery by a digitally controlled machine. I specified size, orientation, and placement - the upholsterer delivered!
 
Rhkansas, I like those rototiller handle bars - not everyone does. That is part of the reason I want to be able to move farther back in the seat. That photo of the 3 XSs - What is the colour of the front bikes tank? It reminds me of my old RD250 in maroon but too much reflection for my eyes to decide.
 
Rhkansas, I like those rototiller handle bars - not everyone does. That is part of the reason I want to be able to move farther back in the seat. That photo of the 3 XSs - What is the colour of the front bikes tank? It reminds me of my old RD250 in maroon but too much reflection for my eyes to decide.
Front bike is my original 1981 XS650H - New Ruby Red
 
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