999 Bp To Mono

he frame on a mono is shorter if you put it on a bip frame it will stick out some cut it down and reweld it
if you can get your hands on the race unit that will go on a bip frame it is longer than the normal mono unit my 749 bip has one on and the frame is the normal bip wanted to keep it so could put the seat back on if ever wanted to problem is these units are about £700 if you can find one
you can get aftermarket ones which will fit the bip frame with nothing to change will be selling one in next few months if you get right one they can look good

 

I cut the top tube off my bip subframe to mount an aftermarket mono seat. If needed I can post a few photos for you to reference?

 

you wanting to keep it so you can put the seat back on if needed

 

I followed Northan's advice got a mono seat unit and chopped my bip subframe, followed his advice and photo's and it looks perfect and no chance of the sub frame cracking as they are notorious for cracking ( mono subframes ). Kept the passenger footpeg mounts so I can mount my panniers too. If you don't want go back to a bip and take a pillion I'd save ( spend on other things) the cash and cut.
His pictures and advice spot on

 

As far as I can see all parts will swap over. Its just the subframe that is longer on the bip and as explained above it can be modified easily. The proper mono frame is lighter though if this is important to you.

 

That would be my plan also, cheaper too.

 

quite the bloody expert at this......mono subframes are triangulated under the saddle but a single loop to support the (heavy) silencer box. Nipped up tight (even though there's a rubber grommet arrangement), road vibration leads to inevitable fatigue wear of sub-frame and pop, they crack. The silencer is held in three points - all of which have been detached in this sub-frame.

Aluminium is more susceptible to fatigue cracking i.e. a weakening caused by repeated cyclical loading, whereas ferrous and titanium alloys have a limit below which no
further cycling will weaken the material. Useful graph attached.
I suspect on some bikes the precise angle of the exhaust tubes and therefore how much weight is taken by the them and the front two mounts as oppose to the rear mount will impact on the likelihood of failure. This frame went a year or two after i bought the bike (so 2005 bike was around 6 years old - hadn't done many miles before I bought it and used it as intended). Frame actually finally went on a track day at Cadwell... following rider spotted a bit of extra movement from the silencer (i had the number plate hanger and indicators off).

So I bought a beefed up frame from the USA. Basically some additional material alongside the tubes - okay for a few years then that went pop at the Isle of Man last year - probably my fault as I have a firm suspension set up, but like to hammer it through Ginger Hall, Glen Trammen. Had it internally strengthened and welded up with double thickness plates and more external bracing.....
Another summer of trackdays and Lincolnshire's finest roads and then the winter lay up. Hadn't even got it painted yet and second ride out this year.....crack. Managed to move the crack higher - this is where the internal bracing ended.

So


Here they are are - both re-welded, powder coated and strengthened with additional plates. RHS is the beefed up USA/IoM, LHS is pretty original but for the internal webs.

RHS is now fitted on the bike and I've managed a Sunday morning .......

I should put up the white flag and either a) stick to smooth tracks b) fit the Biposto and be damned c0 get a squidgy spring

 

you can see the pic above the sub-frame runs close to the exhaust - it's just resting on the exhaust but is usually closer - plus there's supposed to be a heat shield in there too - so you can't run a web down the Z axis. You're right that would be the strongest.

What you cannot see is they now have internal tubing machined down and welded in situ, and then the visible webs you can see should help disperse the stress. I've also gone for a lengthened mounting bolt at the back to allow the silencer to move a little more freely when hammering across the Lincs Wolds.......and some lock wiring should it let go again

 

and a Titanium silencer weighing around 4kg less on smooth tracks...........we didn't see many 999s do the TT

 

the vulnerable area is always where it goes from the triangulated section under your arse into the single tube - either where the bend is or as from #1 at the cross brace. The leverage from the rear mounting point works on the first point of flex.....my first sub frame is the usual failure. The Corse sub-frame is spot on in the design - square tube and more vertical/ It also has two side mounts for the exhaust not one at the furthest point/sharp end of the subframe. Funny that, racing improves the breed.

Apparently many got Ducati to replace these sub-frames even way past warranty. I was third owner and not so lucky. Spent a few quid now....

 

could you stick your photos here

would be interested to see what a cut Bip looks like vs the (cracked) mono..........

 

The additional AV mounts are for the aftermarket seat unit.