Shaping 82 GS850G seat

[Guest]

Slowly but surely got the confidence to start cutting into my seat. Yes, I know, it's supposedly the most comfortable seat ever, but not for me. Just want to dish out a bit and push my seating position back a bit. Also dish out a little more of the passenger area. I seldom ride with a passenger, but 99% of the time it's my younger sister and I'd like her to be comfortable too. I'll probably pick up some rebond this week and make sure I have enough padding in the couple areas I got close to the seat pan.

Rough cuts only last night. Will try to get in there with the grinder and smooth things out. I have an angle grinder that I'm afraid will take off too much. Has anyone used a sanding disc on a drill or die grinder? Or even a sanding block? I don't mind doing it the slow way by hand if it means more accurate results.

[wymple]

I thought the trick was to carve lightly with an electric knife. That's what upholstery shops use.

[growler]

I used an electric knife (kitchen style, not the fancy one for foams specifically) with decent results. However to get in there and contour the foam nice you need something else. Oh wait! I just remembered watching a YouTube video with a guy that used something similar to a Mason Jar lid drilled with a bunch of holes.

Here's the video. What I'm referring to starts around 4 min.

https://www.youtube.com/watch?v=AEsIVPTkk4g

I thought the trick was to carve lightly with an electric knife. That's what upholstery shops use.

[growler]

Here is kinda what I'll be going for.....

[lurch12_2000]

I use the electric knife but have used a hacksaw blade too. The blades have to be real sharp to cut through foam easily and not shred it. After I then use a sanding block and smooth the lines out and round off the edges a bit. Checking by eye from different angles often as I go. If you do take a lot off then the original cover may not contour and sit properly without extra stretching. But you have an after market stitched seam so it's more forgiving with seam placement to match the contour of the new shape. If you had rolled seams or a seam by your thighs, then it might not align properly. Do a little at a time and evenly from side to side when shaping the foam. Easier to buff a little more off as you go than trying to patch foam back on with 3M special adhesive.

BTW, you'd be surprised that any cut lines will show through the vinyl cover. I've used a thin polyfil liner to mask over the foam before stretching the cover back on. It will hide a lot, but make sure it lays perfect without wrinkles. That 3M spray adhesive can lock it in place.

[Chris G]

This is what I used when I re shaped the seat on my Zephyr, using a knife seemed a bit brutal, if you take too much of I would have been gutted, it took a while and was messy but got the shape I wanted.

[Steve]

First of all, be careful that you don't go too thin on the foam. I remember seeing a brief description you gave of yourself a little bit ago, just make sure there is still enough foam there for a comfortable ride. Remember that the foam will compress a bit over the duration of a ride. You had also described yourself as relatively tall, so I can't see why you would be removing much from the seat at all. A little re-contouring, sure, but you have somewhat drastically lowered it, too.

Second, you don't really want piping along the edge, where you leg will be. That is just a pressure point waiting to happen, and will get uncomfortably QUICKLY. It will also be a wear point, as you keep rolling it back and forth as you get on and off the bike.

.

[growler]

I am pretty tall, you are correct. But I'd like to sit a little bit further back than I do. I have some rebond that I can use in case I cut it too thin in some spots. I'm also saving all the foam pieces I've cut in case I need to glue anything back on. This is more for riding position than looks. Once it's shaped I'll take it on a longer ride and see how it feels. Once everything is ok, I'll add a liner to hide imperfections and smooth it out. I read through the diymotorcycleseat site and there's a lot of good info.

I'm going to make a grater type thing out of a lid and see how that goes. I feel A LOT more comfortable using that vs a grinder, even if it takes me forever.

[growler]

I hear what you're saying here, Steve, but I'm only taking about an inch and a half off. There is still plenty of foam underneath me. The only shallow spot I have is back behind my butt. I will add some rebond or add back a little foam in that area.

Let's hope this doesn't turn into a disaster. Hah!

You had also described yourself as relatively tall, so I can't see why you would be removing much from the seat at all. A little re-contouring, sure, but you have somewhat drastically lowered it, too.