Xj900F framy

I may have mentioned before I bought a 900f frame to go with an engine I had previously bought.
Anyway, bit by bit I'm collecting stuff to make this into a whole bike, but not how Yamaha intended. I've allways wanted to go to 17 inch tyres, decent brakes and suspension - although I don't have any issues with twinshock rear, I wanted to try some damper inserts so the front forks can be set up to work, and that might mean going bigger to be stiffer (in terms of flex).
So far I've bought an xj900s rear wheel and arm, an fj1200 front wheel and lower tree (because they were cheap), and a load of plastic bits - battery box, airbox, electrics tray and a few other bits. I have a loom with relays, both switches, although they are for a 600..
Ebay and alcohol has a lot to answer for, and last night, while watching President elect Biden's speech (2.00 in the morning here), Jack Daniels and I bought a set of 600 (yes 600, not 900) front forks. Bugger. £100 mistake.
Anyway, I'm sure I can sell them on. As things progress I might post a picture or two, just don't hold your breath, this one might take a while...

 

Good luck on your 17" wheel conversion. I did that mod last spring 2020. It was a lot of work with the shaft drive (XJ750 Maxim) but really worth the effort in the end. I have state of the art radials tires of appropriate size for a bike of this size and weight
front is 3.50" x 17" wheel with the standard 120/17/70 Pirelli Diablo III and rear is also 3.50" x 17" with matching Pirelli in 140/17/70. Looks great, disc brakes front and rear, and much lighter weight by pounds not ounces (or grams for metric). BTW my forks (complete front end) are 2001 Yamaha R1 properly sprung with 1.0kgm spring from Race Tech. I chose to convert from clip-ons bars to more conventional tubular bars for street riding.
Cheers, 50gary

 

The bitsa is slowly coming together, the xj 900 rear wheel needs some machining to centre it. I've fitted new bearings to the fj1200 front wheel, and with some help from, @FJ111200 managed to find a suitable top yoke. The modified 900 seat goes with the 650 seca tank a treat. Sat on it tonight for the first time, the 900f sure has a long front end - or at least a long rake..

 

A cheap front end for conversion would be Yamaha FZR 600 with Race Tech Emulators and Race Tech Springs (proper tension). Then R1, R6 calipers are a bolt. up mod, then use a Nissin radial master cylinder, stainless steel lines. It will be a new bike. Every 6.4# (2.9kg) you remove from the bike equals one HP.
Cheers, 50gary

 

My bike gained 2 HP this past year, by me losing weight
Only 4 more HP to go.

 

That's an interesting option, too late now though. I'm actually thinking of adding weight to it - turbo, chargecooler and radiator, but am fighting the urge. The 900f frame and fj1200 forks give me 3 choices for turbo placement.
Must fight the urge.....

 

Got my xj900 divvy type yoke on Saturday (ordered in error, not a massive mistake, as things go when mixing and matching). Anyway, it doesn't fit the fj1200, the diameters and widths are good but the offset is at least 10mm different - quite hard to measure...
So in order to keep moving forward I dropped it in my machine vice and took a cutter through it to make the head shaft into a slot. Will decide later if I weld a new insert in or just buy one from an xj6. It means that for the first time it now sits on its new wheels - rolling frame if you like, wheels, seat, tank and rear mudguard. One of the next jobs will be to bring the engine home from work to test the tank fit. (Must fight the urge to fire it up)

 

Pictures?

 

To measure offset of triples put tape (I use painters tape) over the yoke holes at the diameter of the two holes, fork to fork at the diameter of each hole. Then do the same for the third hole (stem hole) now just measure with vernier calipers at the stem hole center to the fork hole line, that's your offset. The measurement will be a T, the base of the T is the center of the stem and the horizontal top of the T is the centerline of the fork holes.
Cheers, 50gary

 

That sound sensible - what sort of errors were you getting (trying it, say 3 times on the same one?) -And, more to the point, do Yamaha use whole mm's, or multiples of 5, or even fractions of mm's? And the big question, did you ever measure an xj6? Or an fj1200? I will try it, let you know my answers, assuming the fulcrum hole is still able to be measured.
Pictures, yes, later this week, I have to get the top half of a milling machine inside tonight before it rains.

 

If you have a pair of Veriners and your forks, put the forks in the triple push them up past the top surface of the triple clamp. Then put any other tube or bolt that is smaller diameter than the stem hole so that it protrudes above the triple clamp.
Place a straight edge on the backside of the protruding fork tubes, then with your verniers measure the overall distance from the straightedge of the fork holes to the tangent (the longest dimension tangent) of the stem. Then subtract half the diameter of the fork tube and half the diameter of the stem tube/pinion. That would be the offset center to center. This would likely be more accurate than the tape across the fork tube holes method. If you get an answer that's in the fractions of a millimeter round it to a whole number.
Cheers, 50gary

 

Went to the workshop to revive this dormant project (I bought a milling machine that had fallen over, it needed some serious repairs, and on top of that some real wear - it’s taken me a year, but working and nearly finished.
I need some rear brake hardware, so took some time to think about it - the problem is the rear calliper stay - it had very little room between the tyre and the rear spring, unless I make it in an “s” shape...
The current rear tyre is a 150, so I’m looking at a less bulbous tyre, maybe a 140 or 130? Then I can machine the wheelcentre to move it across, at least 1/4 inch. I think this will still need the engine moving across to line the driveshaft up.
One plus is at least the engine is home.

 

it is embarrising when you drop your milling machine when out for a ride and come to a red light . hard to restand