Doc's FJ Racer; New mods for 2007

Winter mods for 2007 season

Winter was the perfect time to prep my FJ1100 Racer and also build Liam’s 1TX FJ Racer, which is a carbon copy of my Racer at the start of last season.

First off, was to try and increase the horse power. As mentioned in the previous Journal, I had got the FJ’s motor up to 132hp at the back wheel (standard 108hp) but to be competitive, with the fast Ex-up’s its racing against, it could do always do with some more. I purchased some 1188cc (standard size) high compression 12:1 Wiesco pistons from the states, the old units were 10.5:1.

The barrels were simply de-glazed so the rings could bed in. I had a plan of getting the crank lightened but, when asking around at the NEC show, the tuning shops were all quoting silly figures of £300, so I asked around locally and was told a car tuning shop was in the next village. He said he had never tried a motorcycle crank but was prepared to give it ago. He placed the crank in a lathe and turned a lot of weight off three of the four webs but I had a phone call saying he was unable to remove material from one of the webs. After some thought there was no choice but for me to set about it with a 10” hand disc grinder, not the best engineering solution but I had a budget and the cost was only my time. After spending all night modifying the crank by hand it was back to the car tuning shop in the morning. Again, to save time and money, I helped the guy get the crank balanced. This took about 3 hours, as I had to grind the metal of each web by hand, until the balancing machine said it was spot on. As a reference, I asked him to check a second hand FJ crank and was surprised that it was slightly out which, by all accounts, is normal and within production limits. The final amount removed from the standard 14kg crank was 2kg.

The cylinder head was removed (as last year) and the valves were lightly lapped back in to get full compression back.Due to the increase in compression I was advised to fit a Dyna ignition system, this is fully adjustable for advance/retard and, with a simple flick of a switch, has six different maps. It has a base setting for a high compression 4 cylinder engine which is what I set it on and have left it at that.The complete OE wiring loom was removed and I manufactured a new simpler and lighter wiring loom. This would also avoid any problems with the 24 year old wiring loom that was not actually doing anything except firing the ignition system.

After the bike was assembled with the rebuilt engine, I did 300 miles running it in and a full track day at Mallory to loosen it up. I finally ran it on a Dyno to see if these mods had made any improvements, the first run showed 138.6 hp and because it was running lean we swapped the 125 main jets to 130. T
his knocked it up to an impressive 142.95 hp, I was advised to raise the jets up further so they’re now set at 132.On the FJ chassis I made a few changes, the biggest was the fitment of a lighter Ducati 999 front wheel with EBC discs. I had already fitted a GSXR rear wheel in replacement of the 17” Exup item (saving a massive 3kgs) at the end of last year. The 999 front wheel saved a further 2.8kg, just shows you how much modern wheels have come on compared to 1990 design and manufacture.
For reference, the FJ racer now only weighs 216kg, this compares with a standard FJ1100 at 250kg (saving over 5 stone), Suzuki GSXR1000 k4 at 196kg and a 2005 Ducati 999 at 212kg.
I fitted a maintenance free FJR battery and placed it on top of the engine to lower the centre of gravity.Cooling this high compression engine has been aided by fitting the ignition coils on the main frame in front of the head stock and the raising of the 10 row cooler, from standard, by 50mm.
This now leaves a large gap for the air to flow over the cylinder head that was being blocked by the coils and cooler. The front number plate has been changed, this now has holes in the lower portion, again helping supply air flow over the top of the engine.
This all may seem like small things but they all add up.Other mods include; the fitting of a gear indicator.This works directly off the gear selector (mechanically). It was easy to fit and now I can see at a glance what gear I’m in, because in racing its not something you have time to work out. Also fitted is an oil temp gauge, that neatly fits into the oil filler cap, so I can keep a check on the engine/oil temperature.
The front brake pads have been replaced with Lucas racing pads as the EBC HH pads seem to fade in the race and as a result the lever would come nearly back to the bars. I fitted a new belly pan, the clubs FJ1100 fibre glass unit, but with extra alloy sheet to make a collection tank as per ACU regs (Liam has my old unit).
The FJ OE seat has been modified so I can sit lower in the bike, helping get the Cof G lower and aiding easier knee down which is very helpful in the wet.Now, all I have to do is hope all these mods will make the FJ a bit quicker, but, then again, I’m sure the other guys competing haven’t been sat around all winter either!


Moved coils to frame to aid cooling to cyl head


lowered seat by using Ducati 916 base


Hign compression pistons but still standard 1188cc

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