"The 70mpg FJ1100" - Getting more from your FJ1100

[Anti-Dive Dave]

The following article was published in the British bike magazine "Practical Sportbikes" - Issue 26 - December 2012

I have posted it here in general discussion, and a moderator/Admin can move it to the relevant file section (Modifications or Maintenance etc)

The 70mpg FJ1100

You don't need to buy a boring modern bike to get parsimonious fuel figures.  Phil Hackers 25 year old FJ1100 has been made frugal and fun.

PHIL HACKER is not a man to back down from a challenge.  He does, after all, race an FJ1100 that regularly beats R1s, and makes his living specialising in the venerable air-cooled Yamahas.

So, when he decided his intention to get 70mpg from an FJ1100 at 70mph, and 60mpg at 80mph, few batted an eyelid, let alone doubted his ability to deliver on his promise.

"The BMW F800 and Honda NC700X seem to be the only bikes offering reasonable fuel economy.  Modern cars manage more than 50mpg, yet are five times the weight of a bike," says Hacker, "so the question I asked myself was, 'why can't my bike do 70mpg?'"

Phil feels that we only have ourselves to blame. "We've never demanded decent fuel economy from the manufacturers.  We all seem to want 150bhp and 180mph in something the weight of a crisp packet...or do we? On our busy roads, we generally ride around at 80mph, so what is the benefit of my FJ having a 150mph top speed?  I knew I'd gladly trade some top end for better mpg."

First step in the project he'd dubbed "mission Impossible", was for Hacker to look at the FJs fuelling.

"Dyno testing over the years has shown that the FJ runs rich.  This was a deliberate ploy on the part of Yamaha for engine longevity in hot climates," says Phil.

A baseline run showed that the FJ was delivering 44.8mpg at 80mph. Dropping the needles one notch, advancing the ignition four degrees by slotting the backing plate Burt Munro style, and fitting smaller jets specified for the Swiss market helped it to 55.37mpg – a 23 percent improvement.

At 70mph, the FJ now gave 66mpg – a huge improvement over the previous 54mpg.

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The next weapon in Hackers armoury was gearing, lowering the engine rpm while still maintaining the target mph.  Standard gearing is 17/40 and after some experimentation, he settled on 19/38.  Phil is also a fan of the "Broquet fuel catalyst" and gives that some credit for 80mph consumption of 62.6mpg at that point.  A slight flatness in acceleration above 3000rpm was corrected by enlarging the carb diaphragm slide hole.

Around that time, a Dyno run revealed that the 80,000 mile engine was down to 97bhp.  A good standard FJ makes 108bhp.  Compression was still tolerably good at around 90-110psi (cold).

"Kent cams" had been very interested in Hackers "mission Impossible", and had reground a set of OE camshafts for better fuel consumption and increased torque at low rpm.  In the process of fitting the Kent cams, it was obvious that the FJ had had a seriously stretched cam chain, and this and the power loss eventually led to a top-end overhaul.

Meanwhile, a Metzeler ME880 160/80-16 rear tyre with its larger diameter helped to lower the gearing to give 80mph at 4000rpm.

Testing the FJ against the Honda NC700 at 80mph saw the Yamaha deliver 63.6mpg against the Hondas 70.7mpg.  There was still some way to go to match the frugal NC700, but Phil wasn't done yet.

"My next step was fitting a set of XJR1200 inlet manifolds.  The theory was, that the reduced inner diameter of these manifolds would quicken the flow of fuel and air and aid combustion, but I was worried about it affecting the 80mph goal.  I reduced the idle mixture and the size of the air jet to richen up the mixture at low revs.

The final pieces of the puzzle were restrictors in the headers to increase back pressure, and a home-made 38T rear sprocket to give 80mph at 3700rpm.  Phil fitted a non O-ring chain, and reverted to the standard air jet and filter.

The result?  At a steady 80mph, the FJ1100 now returns 69.12mpg.

Having exceeded his own target, you might think Phil would be happy?  Well, almost.  "There's more to come yet," he promises.  With Phils track record, we believe him!.

Practicle Sportsbikes, Issue 26, December 2012

[Flying Scotsman]

Wow impressive.
Best I ever got was 42 mpg I think.

[movenon]

 

[Arnie]

70 mpg from an FJ is very impressive. 
58.8 mpg for US gallons is also pretty impressive.
25.01 Km/L , again impressive
as is 4.0 L/100kms

All above numbers describe the same fuel use economy.

This is a UK magazine and you should be aware that they are almost certainly using UK gallons.
I really don't care what units you use as long as you identify which of them you are using.

Cheers,
Arnie
 

[Flying Scotsman]

 
Run those gears at 10500 rpm and I think thats 204 mph.If you can keep the back wheel planted and not spining.
Would not help fuel consumption though.

[carsick]

Do keep in mind that those MPG figures are dyno steady state numbers, no wind or front tire resistance, already up to temp (no choke) and never a start/stop. HUGE difference from real world MPG. Can you run a 19 front without cutting the cover? And yeah, like Arnie sez, UK gallons. 

[1tinindian]

 a Metzeler ME880 160/80-16 rear tyre ?

I bet that fit like a saddle on a sow!

[Anti-Dive Dave]

a Metzeler ME880 160/80-16 rear tyre? I bet that fit like a saddle on a sow!

I am currently running on the back of my FJ1200 (1987 1TX), an Avon Azaro AV36 160/80-ZR16.  As you can see, it's ZR rated, and I will never ever get the benefit of the money that was spent on it.  It's perfect for those who run around at warp factor 4 speeds all day....but not me.

My next tyre choice will be the Metzeler ME880 160/80-16.

It's not hyper speed rated at the V, VR, ZR etc, and is more commonly found on the likes of Goldwings and other large tourers.

But, for those who don't ride fast, this rear tyre will suit me to the ground.  I've heard a lot of good reports on em.

Personally, I think it's a waste of money fitting high speed rated tyres if the rider won't get the benefit from them.  Understandably, it will only affect the performance and handling of the machine if I ride the bike like a loony, with crazy speeds and hard cornering.  But I don't ride like that, so, according to many motorcycle magazine reports, they also agree it's a false economy spending money on a high speed rated tyre, if yer never gonna reach those speeds.

As I am a laid back, "Captain Slow" rider, I like the fuel saving side of things and a tyre that can spread a heavy load occasionaly. Forget chicken strips...I still have the whole bloody bird on each side of my tyres.

Since riding, I have kept every fuel receipt and have worked out my fuel consumption.

I average around 45-48mpg (UK gallons) riding at between 55mph and 75mph. Which for an old bike and heavy luggage, that's pretty good to me.  The main speed I stick to is around the 55/60mph.  The occasional overtake at 100mph and a silly cobweb blow out sometimes around the 120mph mark.  I use the engine to brake a lot, rarely touch the actual brakes and try to keep the throttle on "tickover"...which means the bike is appearing to move under it's own momentum, and I only use the throttle to keep it up to speed.

Sounds daft.  But if you drive a car, and get up to speed, THEN take your foot off just a little so you are not physically driving the engine, you'll find the car will pull itself along.  You can use the gas peddle to then feather the vehicle along - thus saving fuel.  Maybe someone can explain in a more technical way.

ANYHOO - for those in the UK wanting to calculate your MPG:

1. Fill the tank to the brim.  Set Trip.
2. Re-feul to brim after journey.
3. Take the amount of litres it takes to re-fill.
4. Convert litres to gallons - divide by 4.5864
5. Take mileage of journey, and divide by 4.5864 = vehicle return mpg.

The faster you go, the more fuel the bike uses...and the more money you have to spend on filling up more often.
The faster and harder you ride, the quicker you'll fuck up your chain and sprockets - made worse if you are a sloppy gear changer. (you hear many riders pulling away on fast sports bikes, rev...rev...REV...and then it's 1st-2nd-3rd-4th-5th before they are even 100 yards down the road.  LAUGHABLE to hear them, seeing how fast they can go through the gears, and still only be doing 30mph in a built up area.  That uses fuel and makes you look like a dork. (in my eyes)

I block gear change on my bike.  I pull away in 1st ONLY if the need takes it.

Once away in 1st, I change to 3rd, and then 5th.  You will save fuel like this, if the gear changes are smooth and match the engine speed.  To slow down, look WAY ahead at the traffic, and use their brake lights as a guide to slow down - leave the gears alone (and the clutch leve - NO coasting), and just roll the throttle off.  A good rider can be followed by an examiner, and on bends/corners/the front rider rarely lights up the rear brake light.

[SlowOldGuy]

If I wanted gas gas mileage, I'd go buy a scooter.  That's not the point of owning an FJ, even though they "can" get very good mileage when ridden conservatively as you describe.

I communte to work on FZ1 and ride between 70 and 80 mph for about 20 miles, then another 10 miles on side streets.

I average 48 to 50 mpg which is about 3X what my truck gets.  Delivering that kind of economy plus the fun it provides on the backroads on weekends, it's a pretty good deal.

Like I said, if it was just about mileage, I'd be riding a scooter.

Also, I got great mileage out of a Dunlop D401 in 150/80-16.

DavidR.

[93fj1200]

a Metzeler ME880 160/80-16 rear tyre? I bet that fit like a saddle on a sow!

I am currently running on the back of my FJ1200 (1987 1TX), an Avon Azaro AV36 160/80-ZR16.  As you can see, it's ZR rated, and I will never ever get the benefit of the money that was spent on it.  It's perfect for those who run around at warp factor 4 speeds all day....but not me.

My next tyre choice will be the Metzeler ME880 160/80-16.

It's not hyper speed rated at the V, VR, ZR etc, and is more commonly found on the likes of Goldwings and other large tourers.

But, for those who don't ride fast, this rear tyre will suit me to the ground.  I've heard a lot of good reports on em.

Personally, I think it's a waste of money fitting high speed rated tyres if the rider won't get the benefit from them.  Understandably, it will only affect the performance and handling of the machine if I ride the bike like a loony, with crazy speeds and hard cornering.  But I don't ride like that, so, according to many motorcycle magazine reports, they also agree it's a false economy spending money on a high speed rated tyre, if yer never gonna reach those speeds.

As I am a laid back, "Captain Slow" rider, I like the fuel saving side of things and a tyre that can spread a heavy load occasionaly. Forget chicken strips...I still have the whole bloody bird on each side of my tyres.

Since riding, I have kept every fuel receipt and have worked out my fuel consumption.

I average around 45-48mpg (UK gallons) riding at between 55mph and 75mph. Which for an old bike and heavy luggage, that's pretty good to me.  The main speed I stick to is around the 55/60mph.  The occasional overtake at 100mph and a silly cobweb blow out sometimes around the 120mph mark.  I use the engine to brake a lot, rarely touch the actual brakes and try to keep the throttle on "tickover"...which means the bike is appearing to move under it's own momentum, and I only use the throttle to keep it up to speed.

Sounds daft.  But if you drive a car, and get up to speed, THEN take your foot off just a little so you are not physically driving the engine, you'll find the car will pull itself along.  You can use the gas peddle to then feather the vehicle along - thus saving fuel.  Maybe someone can explain in a more technical way.

ANYHOO - for those in the UK wanting to calculate your MPG:

1. Fill the tank to the brim.  Set Trip.
2. Re-feul to brim after journey.
3. Take the amount of litres it takes to re-fill.
4. Convert litres to gallons - divide by 4.5864
5. Take mileage of journey, and divide by 4.5864 = vehicle return mpg.

The faster you go, the more fuel the bike uses...and the more money you have to spend on filling up more often.
The faster and harder you ride, the quicker you'll fuck up your chain and sprockets - made worse if you are a sloppy gear changer. (you hear many riders pulling away on fast sports bikes, rev...rev...REV...and then it's 1st-2nd-3rd-4th-5th before they are even 100 yards down the road.  LAUGHABLE to hear them, seeing how fast they can go through the gears, and still only be doing 30mph in a built up area.  That uses fuel and makes you look like a dork. (in my eyes)

I block gear change on my bike.  I pull away in 1st ONLY if the need takes it.

Once away in 1st, I change to 3rd, and then 5th.  You will save fuel like this, if the gear changes are smooth and match the engine speed.  To slow down, look WAY ahead at the traffic, and use their brake lights as a guide to slow down - leave the gears alone (and the clutch leve - NO coasting), and just roll the throttle off.  A good rider can be followed by an examiner, and on bends/corners/the front rider rarely lights up the rear brake light.

Different strokes for different folks. Personally, if all I was thinking about was mileage, I would go out and buy a new little car like my 70 year old mother did.  She gets 55-60 mpg.  I am interested in knowing the mileage of my bike so I will know how far I can go before filling up again and not being stranded on the side of the highway but it is not a determining factor in why I drive my bike or how I drive my bike.  And before I changed over to my 17" 5.5 Suzuki rear wheel, I was running a 180/70V16 and it was great.  Not as good as the 17" by any means but better than stock size.

[Anti-Dive Dave]

If I wanted gas gas mileage, I'd go buy a scooter.  That's not the point of owning an FJ...

You mean the whole point of owning an FJ (be it an 1100 or 1200) is to ride it balls out everywhere...ride it like ya stole it...thrash it to within an inch of it's life?

I think when it was launched, it was classed as a "sports tourer".  Giving the owner a choice whether to hammer it down freeways and motorways....get his knee down on a corner of a race track, or, use it for plodding round the planet in comfort and style.

I bet there are many FJ owners who just use the bike as a get around.  A town bike.  Never toured or been on a race track.  Some never seen the ton.  Some, like me, are not into the sports performance and tweaking it to get that extra 0.0000005 bhp.

I ride it cos I like the look of it.  It fits my lanky frame, and has 2 wheels.  It has the capability to haul HUGE heavy loads that other bikes in my past have failed at.  It returns reasonable mpg for its age and it handles better than "some" modern bikes.

It was cheap to buy (although I spent shitloads getting it roadworthy), and it's cheap to run (ish).  Insurance is cheap too.

I am not a biker, but a guy who rides bikes.  Scooters only manage 30mph and have dangerous little wheels.  So, I went for something that has that little extra poke should I need to.  It alkso doesnt take me 4 hours to cover 30 miles and all I can fit on it is a half eaten sandwich under the seat.

Horses for courses Mr David Sir!  Every rider is different, but the end result is the same: We all choose to ride bikes.  It's just that not all of us choose to ride like there's no tomorrow!

Remember:  Being 5 minutes late in THIS world, is better than being 5 minutes early in the next.

[fintip]

The FJ was launched as a balls out superbike, and was hailed as the winner of the superbike war of '84. It was only because Yamaha went with another platform that they slowly started repurposing it as a sales tool as a sports tourer...

I HIGHLY doubt there's an FJ in existence that has never seen the ton.

I rode  125cc scooter 350 miles in a day once, mostly at 60 and 70 mph. Got damn good gas mileage, too... And I had a milk crate to fit as much as I ever needed to carry (obviously didn't tour on it...)

Not being 5 minutes late isn't why I ride hard. I ride hard because a life lived as safely and conservatively as possible is a life wasted...

As for gears, I don't rev at the lights and I shift up to 5th as soon as possible in town, unless I'm in stop-and-go... You get the best economy in 5th. You're the one who sounds like a dork to me...

[Anti-Dive Dave]

 

[fj11.5]

 

[SlowOldGuy]

If I wanted gas gas mileage, I'd go buy a scooter.  That's not the point of owning an FJ...

You mean the whole point of owning an FJ (be it an 1100 or 1200) is to ride it balls out everywhere...ride it like ya stole it...thrash it to within an inch of it's life?

Where did I say that?  Perhaps you need to work on your comprehension.

My comments were directed at Hackler's mods.  I'll bet when he's finished he's going to have an FJ Turd that a Chinese knockoff scooter will outrun.  I also like his comment about cars weighing 5 times as much.  Weight has minimal impact at speed, it's wind resistance.  The aerodynamic drag coefficient of most cars is a fraction of what a motorcycle is.  He'd probably do better to work on bodywork drag instead of engine efficiency. 

I remember an article back in the '80s when a lot of bikes started coming with full fairings.  Someone calculated that at 150 mph, it takes only 12 HP to overcome the internal friction of the drivetrain.  Unfortunately it took about 150 HP to push the air out of the way.

My point is the FJ delivers decent mileage in stock trim and is fun to ride as fast (or as slow) as you want to.

Let me put it this way:  I'm going to mod my FJ for maximum fuel mileage ... yawn ..... zzzzzzzzzzzzzzzz

DavidR.