FJ Racer; Building Page 2



The Flatslide carbs were stripped and cleaned, I plan only to use these if I find a advangate in power as I don’t like the heavy throttle action that comes with it.
As back up, I modified a standard set of carbs by fitting a DynoJet kit so they would run without the airbox (I fitted S&B fitters to aid engine life).
I set it to the stage 3 settings i.e. 112# main jets (though after the Dyno run I fitted 118#), dynojet needles set on number 1 groove. On testing I noticed that from 2,000 to 4,000 revs it was a little slow on picking up due to the increase in air flow so I changed the air jet from the standard 155# to 125# (though dynojet recommend using 139#).
This seemed to work a treat and to double check I checked the fuelling when I did the Dyno run. The peak horse power worked out at a respectable 117 bhp at the back wheel, considering the engine only had 400 miles on and was still had to loosen up, it wasn’t a bad figure. (As a reference an FJR1300 produces 120bhp).

Carbs; note crankcase breather


Originally I planned to use the 3CV forks, so they were stripped and new fork bushes and seals were fitted throughout. K Tech progressive springs were fitted and using 10/40w oil I set the oil level to 150mm (OE level is 169mm). This gave a rider preload setting of 35mm on the minimum fork preload setting.
Once I got the FJ on the road I realised that I would need even better brakes than the 298mm 3CV disc’s could offer so I purchased a FZR1000 Genesis front end complete with yokes from ebay. This allow’s the use of 320mm disc’s and I could still use the R1 calipers without the need of manufacturing brackets to suit the bigger discs.
The rear shock was U/S. It was the original unit and it was well past its serviceable life. The quest was to fit a GSXR1000 rear shock as I already had one in the garage; I had no problem getting it to fit with the aid of the 3CV linkage arm but after many hours working out the linkage ratios etc.. the 8kg spring and the units damping were not up to the job, as a 20kg spring was closer to the mark. So I refitted the FJ1100 linkage unit and fitted a Penske shock (£530). The reason for spending such a large amount of my budget on the shock was; it’s no point having 120bhp and wobbling around the corners on cheap suspension. (I didn’t choose the Hagon unit as for a track bike you need compression damping adjustment which it doesn’t have.)
The Penske unit is a top grade shock with compression and re-bound damping, adjustable pre-load via a locking screw thread. Another benefit was the built in ride height adjuster which would allow me to adjust the rear height of the bike so changing the steering geometry for quicker turning or/and ground clearance. I set the rear preload to 25mm, from a bike with no weight to when I was sat on it. To achieve this I compressed the spring 25mm from its free length. I set the shock ride height to offer another 15mm over stock height, measured from the swing arm.

rear shock

Penske rear shock with compression and rear rebound damping

handle bars

Renthal Handlebars fitted to Genesis 1000 top yoke.

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