Chris O'sullivan edited a doc in the group: Yamaha FJ 1100 1200 and 1300 sport tourer - LATERAL FRAME CONCEPT -.

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Hi guys, as you`ve seen the odd photo of a partial FJ with YZF750sp swingarm i`ve posted, i thought i would post an overview and progress thus far.

Bike in question is a 1990 3cv FJ1200, currently with 44000 miles on the clock, it was 100% stock when i bought it 3 yrs ago, first mod carried out was the front calipers upgraded to the gold spot R1 calipers with steel braided lines, then the rear was jacked up by 2" which in turn was followed by the GSXR slingshot 5.5"x17" rear wheel and then the 3.5"x17" front wheel from the yamaha exup, which is straightforward, just needs a bearing change and insert shims for the spindle. well worth doing and transforms the handling, bringing the bike bang up to date, at which point, i was happy and thought i was done fiddling, then someone told me they had the YZF750 swingarm lying around.........

The build plan is to fit a YZF750sp rear end and a Thunderace front end to Rex, and to paint him up a bit, ideally to be instantly recogniseable as a FJ1200 3cv but make people come back and scratch their heads

YZF750sp swingarm is a straightforward swap, the pivot dimensions are identical and the shock placement is central too, and that is where the easy bit ends. you need to change the rear shock for a slimmer one, i ended up using a YSS unit from a XJ900 Diversion, the top mount needs two 5mm spacer washers as its 10mm narrower than the FJ shock, and the shock is 15mm longer than the FJ so the std dogbones can be retained and still keeping the 2"lift at the back. the battery mount spar on the top shock mount needs to be removed, as does the remote adjuster mount on the RHS of the frame. and the RHS inner mudguard mounting lug, the inner mudguard also needs trimming back by 4" to clear the bracing boss on the swingarm, the footpeg/exhaust hanger plates only just clear the swingarm so i made up new kickplates and rearset mounting blocks, the pillion footpegs are alloy pegs from a YZF750 so a mounting plate has to be made and welded to the subframe. the sprocket alignment was easy enough to sort, just by reversing the front sprocket from a honda blackbird and machining the boss from the outside to allow the retaining nut to fasten up. that is it so far, I will update as and when, also update bearing numbers etc, as well as the L-ion battery that i use for its smaller dimensions. budget is tight so it may take a fair few months to complete.

So far the parts fitted are as follows

YZF750 swingarm, rear wheel, disc ,caliper,hanger and torque arm, sprocket and spacers ( fj sprocket can be used) 6206 2RS bearing for sprocket carrier, 2off 60/28 2RS bearings for rear wheel and a 40-62-6L seal for wheel. 2off TA2525z needle bearings for swingarm pivot, and 2off TA1715z needle bearings for shock pivot (dogbone)

11 feb 2016

since my last update, things have progressed a fair bit, the thunderace front end fell by the wayside and in it1s place, a 98 R1 4xv set of forks were fitted to a yzf750 bottom yoke, the headstock shaft was pressed out and replaced with the FJ stem which fits straight in. top yoke is from a later model FZ1 for the time being as the cost of having a stepped top yoke machined is out of my budget range for now, a thunderace front wheel has also been used so as to keep the std speedo, for this the inner boss on the LHS fork leg has to be machined off to allow the speedo drive to be fitted. i then drilled and tapped a hole to take an M5 x 8mm bolt into the fork leg to act as a retainer to stop the speedo drive rotating and fitted FZ1 bars to the top yoke. front end is now in place and everything works as it should up front. R1 discs,calipers and fork legs, thunderace front wheel and speedo drive, YZF750R bottom yoke and FZ1 top yoke and bars. once the paint is finished and bodywork screwed in place i can check the lock stops and adjust as needed.

13 March 2016

so near yet so far away, bodywork is back in place, and for the time being i have decided to shelve the rearsets and modify the standard footpeg hangers slightly so the rear brake gubbins clear the swingarm, this means machining a recess into the base that the rear master cylinder bolts to, as well as where the brakelight switch clip sits. this will be done tomorrow. Fred Greenlee has sent me a rather tasty screen for my fairing and that should hopefully be arriving this week, as will the exhaust cans (carbon ones). and out of respect for my advancing years i have gone all mushy and hi-tec and purchased some heated grips.. test ride within a matter of weeks i hope :)

06 April 2016

Test ride complete.... nothing fell off,bottomed out or self destructed, that`s the good news. a few niggles came to light, nothing major, just tweaks, firstly, the thunderace speedo drive runs through a reducing compensator, which on the FJ reads 40mph flat out in 3rd gear, now even running 16/40t gearing, i should be well north of 80mph at this stage, secondly, the 16t front sprocket might be a tad small, so a 17t will be fitted, and the rear sprocket adjusted accordingly, and i need to replace my rear brake light switch which has decided to pop its cloggs through sitting in a drawer for 8 months. final measurements on wheelbase tally in at 56 & 7/8ths inches, 2 & 1/2 shorter than stock. handling is a lot sharper, front will lift on demand but still feels stable ( once roadworthy certificate has been issued i will do a proper roadtest) forks still need tuning for optimum performance, and the yss rear shock seems to do what is asked of it. all in all i am very pleased with the transformation

%d comments
  • before the stripdown

  • with swingarm fitted and one of the paint designs i was toying with

  • You'll get there Chris :-)

  • Hi Chris, you might find that you will need different dog bones when the Ace forks go in, they are shorter than FJ ones by about an inch so the steering really quickens up. I know 'cause I have ace forks in my FJ.

  • thanks Chris Pocock, will take that into consideration, so far i`m still getting the rear end sorted, the fun obviously starts once the build is complete, that`s where the fine tuning and really usefull info will be found

  • How are you liking the YSS shock?

  • Haven't had it on the road yet. Hopefully in the next month to 6 weeks

  • Ohh you went the YSS route . let me know how you get on with it mate . I was going to go that route til i found the 640 . Looking good mate !!