Fastback tail fairing on a 850 frame

I want to fit a Fastback tail piece to my 850, but my frame is one of the wide rear loop ones.

Several years ago, someone in the US used to advertise for a wide version of the tail fairing, but this is no longer available

Has anybody here tried cutting the rear loop to narrow it down?

It looks to be not so difficult. I can see 2 ways of doing it -
Either cut the necessary section out of the rear bend over the mudguard, then bend the tubes just aft of the shock mounting points so that the cut ends meet, then weld them.
Or simply cut the whole rear loop off aft of the shock mounting points and either make a new loop or do the above cut and shut.

Is it necessary to place a short piece of tubing inside the cut as a splint? What about distortion when cutting the frame?

/Steve in Denmark

Joining the tubes, machine a double sided bar to the inside/outside dia of the norton tube, and braze it in, drill a small hole in the tubes to let out the expanding gas.

stronger than weld and align's the two cut halves

Is THAT Neccesary ! ? :x

Measure the width across the frame , and the tail fairing in the same locations .

Likely grooveing / relieveing the inner sides of the fibre glass at tube position
would get it shoe horned on . just a clean up and RADIUSED rebate Where Required .

Fit it and mark poition with builders pencil before sculptureing / carveing work .

I have fitted a fastback fairing to my 1973 850. From memory, fitted back in the mid 90's, I just had to relieve some material from the fairing to get a snug fit. Sorry no pics as I cannot get it to work.

cheers george

Found the frame width dimensions at http://atlanticgreen.com/commandoframes.htm page - he used to do the wide tailpieces:

4. Rear frame loop width. Normal 6 3/4" (will accept fastback tailsection), Wide 7 3/8". Measured between the frame rail tubes 4" forward of the rear of the rear frame loop.

With this much difference in width, its just not possible to resolve the fit by removing a bit of the fiberglass I'm afraid.

/Steve in Denmark.

It would be cheaper and easier to run a bandsaw down the centre of the tailpiece, and resin in an extra 3/4" of width to the tailpiece.
Lot easier and less damaging than cutting and welding the frame !

Unless it (the tailpiece) is already beautifully painted ?

I will check again but measuring both my 71 Fastback and 74 Mk2a got 260 mm at the widest point of the rear loop on both frames.
The Mk3 frames are wider ?

Time Warp said:

I will check again but measuring both my 71 Fastback and 74 Mk2a got 260 mm at the widest point of the rear loop on both frames.
The Mk3 frames are wider ?

Click to expand...

Depends on whether your frame was Reynolds or Verlicchi made, and what day it was made ?
Rear measurements vary, according to DynoDaves table of measured frames...

Rohan said:

It would be cheaper and easier to run a bandsaw down the centre of the tailpiece, and resin in an extra 3/4" of width to the tailpiece.
Lot easier and less damaging than cutting and welding the frame !

Unless it (the tailpiece) is already beautifully painted ?

Click to expand...

No way, it would be far easier and faster to just cut an appropriate size section (symmetrical about the weld that is already there) out of the back mudguard loop, bend the ends together and weld it back up. If you wanted to get tricky with it, once cut you could spread the rails a bit and tack weld something between the frame rails where they start to bend in (to give a node to bend around and some distance to account for springback), then bend the ends in, remove the spacer and weld the ends together. Splitting the tail piece and making it wider may be possible but it would not be easy or fast if you want it to look halfway decent, how are you going to blend it into the tail light lens?

Cheesy said:

.. how are you going to blend it into the tail light lens?

Click to expand...

After you sectioned the Fastback seat,fuel tank and shock mounts,you would do the same to two NOS L679 tail light lens. :lol:

Whats the problem,mark the center line , cut out the difference, brace were you want the bend to start and weld back together. The very rear section of the seat rail is a really high stressed area and your frame may explode due to doing this

Time Warp said:

I will check again but measuring both my 71 Fastback and 74 Mk2a got 260 mm at the widest point of the rear loop on both frames.
The Mk3 frames are wider ?

Click to expand...

Its not the max width that is the problem, on my frame at least the seat rails are parallel until about 230mm back from the main frame tube, then they are angled in to the loop at the back

I gotta say, I'm siding with Matt on this one. To me, making the fiberglass tail section fit the bike is a better way to go than making the bike fit the tail piece. Cj

IF you Really Must ;

you need to do a bit of carpentry . Make some blocks to fit inside the rear hoop / loop , and ones over it . then get out the fencing wire or run over it with the pick up ,
Though a Bottle Jack & a door Frame ( a closed secure gap , to set up for ' the big crush ' in ! :x

RIGHT , a 2 x 4 cut to knock between the shock mount area . More sophisticated would be contured hardwood end pieces , and a knock in 2 x 4 , useing a Big Sledge & GENTLE knocks .
Looking aft , youll need to decide where to fix the width , and carpentrise a spacer with ends contured to mate to rails , Or two to mate rails ( thisll let it CURVE if theyre ACROSS
the spacer , rather than a end ( of them ) on spacer edge . that likely needs tying off to the rear so it wont slip / slide .

NOW , we get a hardwood ? 2 x 4 with a groove mateing the loop tube on inside 4 in , one ea side , outer . And put No 8 wire ' X ' ed . over under over , pin at center , WIND IT ON .
the tautening / tensioning will judiciously 8) pull the sides in closer , evenly ( we Hope :| ( this is where a positve disposition is necesary . If youve not got the better of youreself , youll have to take yr time . Induceing it to bend to your will is required ) )

Alternately , lying it on blocks , prefferably dead horizontal , on the contured packers , with the spacers in .
AND with the bottle ( hydraulic ) jack and a stick ( 4 x 3 ? ) to a BIG rafter or Ceiling RSJ / RHS ,
jack one side in , till it gives a notch , Flip Over , Get other side similarly compying . ( THIS is with the SPACERS IN )
Then you can push one side in say 3/8 , then the other , preferably alternateing as you go quitely TO KEEP IT STRIGHT / On Centerline .

That way you dont have to realign , in the ' re center ' it manner , as its been KEPT on CENTER .

If you happened to go in say 1/8 to far , thats cool , as youll stress relieve it to a degree jacking it OUT a notch .Hopefully . neutral stress at new bends across tube )

The Idea is to have it ( the tube stressing / levering / alignment , PICTURED in Your Mind , so your easing it mildly , not jacking it all over the place .
AND avoiding HARD POINTs , so dont get dings / kinks , packers with spring ( give ) will flex , allowing CURVES , rather than folding it over a hard point .

Likely best avoid the Oxy Gear etc , which can open the pores of the metal , giving future corrosion or inconsistant load bearing ( Kinks Later 0

Its all pretty basic , grabbing a few metres of 1 in Dia. 16 G mild steel welded seam ( Exhaust tube ) TUBE ,
and playing with it in your 6 in Vice with the gloves on , will give you a feel for its propertys .

This is / Avoiding your efforts throwing the rest of it ( forward ) OUT of kilter .

A hydraulic press , like most bike shops have , could be o.k. & holding by hand . If youve a few muscles & keep it flat / square , rather than skewed off .

The Other CAUTION is you DONT want it to ' Spit Out ' or spit spacers / tools OUT , as they could get into your teeth or eyes ,
with the force of the end of a snapped hauser . Ships ones take peoples heads off . So lock up the children or have them wear helmets & goggles if they supervise .

Or just get someone about 20 stone to jump on one side , with it Flat . Then the other . :? :lol:

P.U.I ?

Hi Matt, thanks for the long post, but I'm afraid I really dont understand a word of it.

/Steve.

Or you could make a tail piece to fit...... a lot of work involved in that though

Steve
Hi ,Some time back I built up a MK3 Fastback using a 1973 frame and the tailpiece used I bought from RGM.It was an replica early type (1968) with the rasied section on the rear for attaching a badge,this just fitted straight on with no mods whats so ever.The same can't be said for the piece of crap brand new fastback seat that Fair Spares/Norvil sold me ,Thieving robbers,but thats another story.The frame batch No for my frame is 110026.

Anyway fast forward to 18 months ago of friend of mine was building a 850 Fastback using an original bike and a NOS fast back tail piece,this would not fit over the frame loop. He then orderd a new replica from the UK (not sure where) and this was closer to fitting but still too tight.
So what I did was to remove some of the bonding material form between the inner/under section and the outside skin,wedged it out a little bit without breaking it and rebonded it.Once this was dried and refilled ,I then had to lightly grind the inside of the glass to ease the fit.
I also tried to use some woodwworking sash clamps in an attempt to pull the sides of the frame loop in but this did not work.In the end the tailpiece fitted ,but only just and once the all the paint work was done it became tight,but still fitted on.To this day it is still on the bike and being used.
Hope this is of some help.
Brett

Andover Norton list a Fastback tail as of last month.

http://www.andover-norton.co.uk/News.htm

It might be a exact replica or somewhat universal ?