So, before getting it properly painted I thought I'd see how it looked (and it would make it easier to get the whole lot across the the painters) however the straight swap, easy conversion from bi-posto to mono isn't going well. I have all the bits I need (genuine early seat unit, unknown age seat pad plus all the bits from the bi-posto) but something's not right and rather than launch it into the sky I thought I'd ask on here first. The tail piece on the bike looks alright, gap at the front also looks about right as well However, it's only attached with the hinge on the front, it doesn't have the seat catch on and so the tail piece is resting on the sticky up pillion rubber bungs (which you can see most of through the top vents) and the pads near the other vents are resting on the undertray. But even doing this the riders seat still doesn't rest on the sub frame, there's a gap of 3 or 4 mm between the seat feet and frame so if you were to sit on it, the whole lot would bend. I'm presuming it's not supposed to bend and it's probably something simple (like me !) that I've not got right or is missing but I'm buggered if I know what it is. Hopefully someone else will and can point me in the right direction
Here’s a couple of pages from my old 94 916 Workshop Manual. One shows a mono, the other a BP. May be of help?
I had a 748 BP with a mono seat many years ago - seem to remember some spacers under the rear lock plate or some spacers on the spigot bracket on the tailpiece?
As Ricky says you can buy spacers or you can use the seat catch off the BP seat but turn it around 180 degrees which should then get it to line up with and rest on the lock mechanism on the subframe. I’ll try to find a photo. On yours, the parts circled red should just touch the undertray, the rubber pads are to prevent wear, and the parts circled yellow should rest on the subframe, also circled yellow. I suspect that if you can sort out the seat catch the whole lot will fall into place.
The seat locking plate needs to be bolted to the seat and you ideally should use a mono seat plate. You can see both of these in the parts diagram although they are not numbered. You made need some spacers to get the correct seat height and Ducati used to sell these as separate items.
Perhaps my original post was unclear. I have all the parts I need, the problem appears to be with everything fitted the ribbed seat feet don't touch the sub-frame. For my first go, I attached the seat catch with spacers etc but the whole thing rocked significantly which obviously wasn't right and investigation showed that the seat feet were someway above the subframe. I removed the spacers to check their length but I then discovered that even with the pads resting on the undertray (which I know isn't right), the seat feet still don't touch the subframe. Consequently if I sit on the bike with the seat catch fitted or not, my whole weight would be supported on the hinge at the front of the tail piece and a bit at the back and there's no way that can be right. So I must've done something wrong but I'm buggered if I can see what I've done...
The front of the seat catch should lie fairly flat as it effectively moves in two planes hinging up and moving the seat backwards and forwards a little. From my experience, they don't always sit that well on the front of the subframe. Adjusting the seat locking plate can move the seat back and cause it to lie flatter. On some bikes there are washers under the front seat hinge mechanism as it bolts to the frame, if you have them you can remove them and that will lower the front of the seat a fraction. Depending on how high the front of the seat fits away from the subframe you could try using the rubber ties that are used on parts of the frame to hold wiring in place etc. to build up the height under each rubber seat pad. I have also seen it where someone has snipped the rubbers pins off the seat pad rubbers that push into the seat base and glued an extra set onto the originals thereby allowing the "jacked up" pad to actually touch the frame.
