FJ on a Diet

There's no way around it; by almost any standards, the FJ is a heavy bike. Maybe in 1984 the FJ1100 was an average weight bike for its size—but by 1986, bikes were already getting lighter, and the FJ only got heavier with every generation.

Why is this so?

The Perimeter/Lateral Frame was one of the first of its kind on a production bike (and in that sense was a trendsetter; it's the frame of choice on crotchrockets to this day). And while completely stable at all speeds (not something to be taken for granted in the 80's), the frame wasn't designed with weight as a concern. A steel alloy was used, instead of the aluminum that came into vogue later in the 80's (not always successfully at first, and never as durable). Modern engines are designed with lighter components inside, substituting metals like magnesium for steel wherever stress is low enough to allow; the FJ was instead designed with durability and simplicity in mind.

Basically, lightweight and durable are at opposite ends of a gradient. The FJ engineers leaned towards durable almost every chance they got, and often in excess. Rims, swingarm, exhaust, etc.; all are far heavier than their modern counterparts on modern bikes.

What can you do about it?

Well, the easiest and cheapest way is go on a diet!

Assuming you've gone that route, however, there are several options[3].

Switching the stock exhaust out for, example, a Kerker 4-into-1, saves 21 pounds according to the source above (and this source[4] as well), while the RPM exhaust will save like 25 to 30 pounds according to Randy's measurements. The stock exhaust of an '86 has been weighed at 35.8 lbs., Randy's prototype at the time weighed a little less than 10 pounds. (His production exhaust is expected to weigh more like 6 lbs.)

The next biggest weight savings is likely to be made by swapping out rims for modern options—and generally, the more modern, the lighter. 6-11 lbs (3-5 kgs) lighter. This thread talks about weight of rims and a 1990 FJ, as well as weight distribution.

Removing the ABS system on models equipped with it removes ___. Removing the anti-dive also saves a small amount of weight.

After that, generally swapping out anything for a modern equivalent on the bike will lighten it—from handlebars, to lights, to calipers, to the rear shock, forks, gauges, swingarm, you name it.

More extreme options include lighter screws, material removal, crank lightening on a lathe, frame modification/refabrication (or just drilling out holes of material), subframe chopping,

Doc's FJracer


Pictured above is Doc's racing-modified FJ1100. He gives a complete list of all of his modifications on his website[1]. He did everything imaginable to lose weight, from switching exhaust, removing stands, fabricating a new gas tank, new rims, shaving down and balancing the crankshaft (from 14 kgs to 12kgs), and so on.

On weight, between 2006 and 2008, he finally says,

"The standard weight of an FJ1100 is approx 250kg. The 2007 racer weighted in at 210kg, with the new 2008 mods that was reduced to 198kg fully wet including 6 ltrs of fuel."[2] That's from about 560 pounds to 450 pounds. The FJ1100 was the lightest of the FJ's; later models weighed as much as 590 pounds. For reference, the 2010 R1 weighs 448 pounds wet, though the 2005-2006 model was a bit lighter.

Later, he drills holes throughout the frame (a cheap alternative to manufacturing an aluminum alloy replica), and replaces all fasteners with titanium equivalents. The next year he hacksaws off every non-essential bracket, and replaces the engine mounts with home-made alloy pieces. He also replaces the battery for a tiny lithium unit.

Some other mods may have added some weight (a new head with steel valves, et al), but he ends up with a 192kg (423lbs)(!) FJ, about 125 lbs lighter than stock, and lighter than the lightest 430ish pound R1 from '05/06.

Replacing the rear shock with RPM's replacement saves 3 pounds. [5]

German FJ track bike???

This beauty was reduced to 190kg (420lbs) as well, but little is known about it in English speaking communities. Fairing is believed to be off of an FZ750, swingarm off of a GSXR.

What i've found out so far!! German built, 191kg, PVM alloys, GSX-R750 K3 swingarm, original frame/subframe modified/shortened, front end KTM 990 Superduke +, all fairing FJ (partly modified). except screeen (MRA), mudguard, one-off seat and bellypan, remus pipe with scorpion end can, 41mm Mikuni flatslides

the fairing looks more like a modified FJ600/XJ900 fairing than an FJ1100 or FZ750…jmho…one of the most amazing FJ's I've ever seen!!! Is it in the Fastbikes magazine? If so, what issue?


"XJR1300 pistons, head work, Mikuni TMR36 flatsides, akropovich 4-1 with scorpion silencer, strengthened frame, KTM superduke forks, RC8 radial brake calipers, PVM wheels w/ continental slicks, swingarm is GSXR750 K2 (but want to fit an SRAD swingarm), wheelbase 35mm less than standard; new swingarm 40mm shorter again."

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