What I built this weekend

Ever since we did a rebuild of my bikes on a new frame in 2005, the meter console had never been quite right - We'd replaced the original wiring and console of the Lightning with the Thunderbirds.

The chromed plastic bowls had been quite scratched and the mounting stubs broke, and so we ended up taping the meters together with duct tape. In time I replaced the tape with a strip made out of two red bull cans. Skillfully disguised, but still tacky...

So this week I had Thursday and Friday off, so I decided to build a new console - I started with this :

A 87mm inner dia copper pipe (funny that my bikes piston is exactly this size! )

I'd looked for aluminum or brass, but no one was selling me a piece shorter than 12 foot. Steel and SS is just too painful to work by hand.

First sawed it with a hacksaw, filed and deburred the edges, made a three inch piece for each meter

The pipe pieces were slit lengthwise to allow the meters to fit in.

Another segment cut and drilled to join the two together - Phew! Sawing this 3 mm pipe by hand is a real bitch.

Bolted together with some SS fasteners salvaged from an old motherboard.

Added two more bolts, threaded into the copper - The screws are tough enough to cut their own thread. A slot was cut in both sides and the bolts washer slots into it.

A spacer is bolted across the two pieces and the thick SS bolt holds the entire thing stable. It's well below the bottom of the meter innards.

An L shaped bracket made from some scrap I had lying and a aluminum thingamajig to fit the ignition key switch.I had to drill that hole with a Stanley power bore bit, it managed quite well in aluminum. Not the most sturdy thing, but it will do.

Spray painted the whole thing matte black.

Found a part of the old console and cut the piece of it, drilled holes for LEDs and wired them up, replacing the old bulb based indicators.

It took me three days to build this, I used a hacksaw, files, a drill machine, and a Dremel moto tool. It's not the most perfect thing with sub millimeter accuracy, but it works and looks good!!

Back and forth, left and right

There's a lot of riding folklore out there, passed on from the mists of time... Not all of it is accurate or logical.

One of the most common myths is about the use of the front brake - Indeed as a kid, when I first rode a bicycle, I was told by my friends "Never use the front brake! The bicycle will somersault!"

I was too dumb then to realize that physics does not bear this out. Indeed I never ever did use the front brakes on my bicycle ever, for the brief time that I did ride one!

When I graduated to a motorbike, however, I had read enough at msgroup.org and various other locations on the internet to realize that the front brake is where it's at.

My first motorbike was an Enfield Bullet Lightning 535 as seen here (this is not my bike)

It's essentially a beefed up 500 bullet with :

• 535 cc's - Bore 87mm vs the 84 mm of a 500, producing a claimed 26 crank HP, and bigger oil rocker feed lines.
• Fritz Egli design "high speed" forged piston - a real lemon - this piston is prone to seize or become very loose and clattery - also they cost a fortune. Thankfully I never had one seize, although the first one cracked - I've since "downgraded" to a solid UK made cast piston, cheap and robust..
• Disc brakes
• "Cruiser" styling

When I first rode the bike, I fell several times, almost always by locking the front wheel on sandy patches. For some reason the cruiser style handlebars and the seating made for a vague front end, similar to the Bullet Thunderbird, and totally unlike the way an old Standard 350 Bullet handles.

The default Dunlop ribbed front tyre didn't help the cause much - for a while I doubted my ability to ride, and was chided by several (non-biking) peers about my "incorrect" braking technique.

After a big T-bone accident I had at about 50MPH  (which bent the frame down tube by sheer impact force), we rebuilt the bike onto a standard 350 frame, while retaining the original handle tee.

Since then the bike handles perfectly, and last year, after the addition of a Pirelli MT60 front tyre, I have never been able to get the front wheel to skid, even under relentless braking. Meanwhile the rear wheel can break traction even under over-aggressive down shifting.

So the whole "use front brakes unless you are in a curve" theory is vindicated.

What I've never been able to figure out completely is why the Thunderbird style seating and handlebars give rise to front end instability.

Here's an interesting observation though - If you trace the paths of ends of the handlebar from lock to lock, you will find a big difference between that of the Thunderbird and the Standard Bullet and how my bike is set up :

Figures are not very accurate and a bit exaggerated since the handlebar is a complex shape, but the idea is pretty clear.

Something radically good in terms of control seems to happen when the handlebar ends are between 9 o' clock and 3 o' clock positions. Gets progressively bad as they come towards 6 o'clock, as evidenced by the better handling of the Standard as compared to the Thunderbird and even better handling on my bike which has the Standard handlebar mounted in the Thunderbird tee yoke.

Perhaps is as simple as the fact that the further ahead the bars are, the more forward the rider weight goes, or maybe its the arc that the arms trace - consider driving a car with the hands on top of the wheel vs. hands at the bottom.

It could be the fact that close to 9 and 3 o clock, lateral movement of the hands is almost nil, only forward backward motion is involved.

Whatever it is, it's quite surprising that mild change in seating position and handlebars alone can affect the feel of a bike so much!

Comparing bananas and lemons - Part 1 : Power

When it comes to motorbikes, there is a lot of partisan attitude, some fanboyism and cliquishness…

Right here we have the Bullet chaps (moi included), the Yezdi/Jawa fans (me included), the RD350 lovers, and the RX boys – Inevitably, there is debate about the relative merits of each and much bragging about top speeds and ¼ mile times.

But, the problem is: How would you go about comparing say a 100cc Hero Honda Splendor with a 1300cc Suzuki Hayabusa? It’s all very well to say that they’re made with different aims and can’t be compared, but actually they can – even though the only common thing about the two is the fact that they’re Japanese designs and 4 strokers.

Looking at the fundamental aspect of a motorbike – the engine – we can define certain parameters that let us place a bike as a point in some multidimensional space and see how it compares to others along different dimensions.

Power

The scientific definition of power is “Work performed per unit time” – no doubt this is the absolute measure of a bike, but then things are also relative – Which is more impressive? An elephant lifting a quarter of its weight, or a slim weightlifter hoisting four times his own weight overhead?

Thus, to measure different classes of bikes we need to normalize the power values.

An engine produces a certain amount of power at a certain RPM with a certain displacement – Ideally, (and this is true to a large extent as you will see later) we should assume that if you double an engines displacement, and maintain the same RPM, you should expect twice the power. The same applies to doubling RPM while keeping the displacement same.
The reason is simply because an engine is essentially an air pump, and the power it produces is purely dependent on how much air flows through it.
 

Thus, the correct way to measure relative power output is to divide the actual value by RPM and displacement.

For example: If a 100cc engine makes 7.5 HP @ 6000 RPM, we should expect a 200cc engine of similar design to develop 15 HP at the same RPM, since it displaces twice the volume as the former in a given interval of time.

Thus one of the first variables we can derive (in no meaningful SI units) is HP/Liter-KRevs - Namely, how many peak horsepower are developed per liter of engine per 1000 RPM – We will call this the K - factor

Let’s look at some famous (mostly from the Indian market) 4 stroke bikes past and present and see where they fare… Note that this data is gleaned from manufactures specs and some of it from reading wheel dyno charts, and adjusting upwards by around 15% to get crankshaft figures.

Japanese bikes

Model`	CC	RPM	HP	K
Hero Honda CD100	100	7500	7.5	10.00
Bajaj Pulsar DTSI 220	220	8500	21	11.23
Honda Karizma ZMR	223	7000	17.6	11.27
Yamaha R 15	150	8500	17	13.33
Honda CBR 250	250	8500	26.4	12.42
Honda CB750	750	8000	67	11.17
Suzuki Hayabusa	1300	12000	190	12.18
HD Sportster 883	883	6000	50	9.45

What can we read from this?

The ubiquitous Hero Honda, seen as the epitome of efficiency in India, is actually close to the bottom of the list – The CBR 250 does 24% better. If you metaphorically grafted 2.5 CD100 engines together and revved it up to 8500 RPM, you would get 7.5 * 2.5 * (8500/7500) = 21.5 HP – The CBR makes 5 HP more! So either more fuel is being burnt, or fuel is being burnt better.

In fact, the Hayabusa is quite astounding! If you grafted 5.2 CBR250 engines together and revved it to 12000 RPM, you would get 26.4 * 5.2 * (12000/8500) = 193.8 HP – Just about 2% more than what the Hayabusa makes on paper – Getting 1300cc to rev at 12000 RPM is no joke, it’s hard rocket science to be able to scale up an engine so well! The Hayabusa is an engineering marvel.

The R15 seems quite amazing, with only 150 cc, it makes almost as much as the 220 Pulsar – Seems like the most advanced engine amongst its peers.

The Harley is nowhere near the rest, even though it is a highly engineered design, but then again it’s a pushrod engine with an extremely under-square design, built for an almost flat torque-curve.

Let’s look at the two popular mid level bikes Pulsar and Karizma – Isn’t it startling that despite all the state of the art technology, fuel injection and what not, a 1970s CB750 of much larger capacity comes within 1% of the figures in terms of our metric?

I tell you sir! They don’t make ‘em like they used to! They just hype ‘em louder.

Of course, we aren’t looking at fuel efficiency (yet), so perhaps this conclusion is flawed; perhaps the bikes that have higher K are burning much more fuel. But nevertheless, if the question is: “How much power can you get out of a liter of engine regardless of fuel consumption?” then the above table shows the answer.

Royal Enfield’s

Model	CC	RPM	HP	K
Diesel bullet	435	3600	7.5	4.79
Std 500	500	4750	22	9.26
Std 350	350	5000	18	10.29
Lightning 535	535	4750	26	10.23
Enfield CL500	500	4750	27.2	11.45
ACE Fireball bullet	535	5750	42	13.65
Hitchcocks 612 stroker	612	5750	45	12.79
Enfield Constellation	700	6250	51	11.66
Enfield Interceptor	750	6750	56	11.06

This had to be in a separate table!

Not much to say here, except that Tom Lyons’ (aka ACE) Fireball kit can take a Bullet well beyond Jap bike territory: The dyno charts for the Fireball charts show about 36 wheel HP, so 42 engine HP is a reasonable estimate.

The Hitchcocks stroker 612 does great too, despite having an even longer stroke, and the CL500 is much better than the old Enfield’s, even considering it has to contend with Euro 4 emissions norms.

Quite surprising that the Connie and the Interceptor of yore do so well for air-cooled long stroke parallel twins.

These numbers are derived from observing several wheel dyno charts, rather than manufacturers specs (which are quite off), 6 HP added to get crankshaft horsepower estimate.

Legendary Classic Brit bikes

Model	CC	RPM	HP	K
BSA Goldstar	500	7000	42	12.00
Velocette Venom	500	6500	41	12.62
Triumph 650 twin	650	6500	46	10.89
Norton 650SS	650	6800	49	11.09
Vincent 1000	998	5500	55	10.02

Just astounding! These were mostly OHV pushrod bikes (except the Norton which was an OHC), ranging from the 40s to the 60s.

The Velocette even beats the Hayabusa in this metric! No doubt it ran on “real gas” but even so – this is a 50s bike with 8.75:1 compression! It still holds the 500 cc 24 hour endurance record at an average of 100 mph+, that too with a stock engine. All the employees of Velocette rode these bikes themselves and the build quality was so good that a stock bike was race ready. A few years after this record, they attempted it again with a souped up 350cc bike, which was going great for hours, unfortunately after 6 hours averaging > 105 mph, the piston blew ( this was not a Velocette manufactured one, but sourced from elsewhere) and the record attempt was thwarted.


The ACE fireball is on par with the Goldie on paper, and that speaks a lot about its potential performance!

I ask you!

Two strokes and four strokes

A four stroke has one power stroke for every two revolutions of the crank, whereas a two stroke has one. That means that a two stoke will (ideally) pump twice as much air as a four stroke of the same displacement at a given RPM.

Thus if we want to measure using the above metric then we need to include a factor of two – This is unfair because usually a 2 stroke of a given displacement makes only about 30 to 50% more than a 4 stroke cousin of the same volume – For e.g. take the Yamaha RX100: It makes 11.5 HP vs. 7.5 for a CD100 – that’s 53% more power, which is impressive, but still not double, even though it displaces twice as much air per unit time!

But fair or not, that’s the metric so let’s look at 2 strokes of all kinds:

Legendary two-strokes from India

Model	CC	RPM	HP	K
Jawa 250	250	4750	12	5.05
Yezdi Roadking	250	4750	16	6.74
Jawa 350	350	5000	23	6.57
Yamaha RX100	100	7500	11.5	7.67
Yamaha RX135	135	7500	14	6.91
Suzuki Shogun	108	8500	13.8	7.52
Yamaha RD350	350	6750	30.5	6.46

The RX 100 is the absolute champ here! Squeezes out every ounce of power from that 100cc, the Shogun does quite similarly. The Roadking has its reputation as a rally and motocross bike and for a 70s design, it is quite impressive.

None come anywhere close to the four stroke bikes, so it’s obvious that if you ride a two stroke, you are throwing a lot of fuel down the exhaust chute…. But then again a two stroke has an exhilarating, almost linearly increasing torque curve all the way up to the top, and who can not be enchanted by the coarse whine of the RX, the scream of the RD350 or the burbling purr of a Jawa?

Really amazing bikes

Model	CC	RPM	HP	K
Maico 760	760	4000	43	7.07
Maico 760 @ peak torque	760	1200	26	14.25
Suzuki RS67	124	16500	41	10.02
Honda Rc 165	250	10500	60	11.43
NSR500	500	19000	240	12.63

Yes, all those numbers are correct! The Maico 760 was a two stroke single, the largest ever made, and perhaps the most “gruntiest” of any bike that I have ever heard of… It makes even a thumper like a Bullet look like a revvy whiner. Stomach churning torque, I say! Look at the K factor at peak torque! That is true “bang” for the buck! Only 6 were ever made…

The other Japanese race bikes are again crazy - the RS67 had 4 cylinders, 12 gears and hit 137 mph – unbelievable!

The NSR 500 is probably the most powerful two-stroke made anytime, anywhere and needs just about 2cc to make a HP!

One thing that’s quite clear to me from real life experience is that manufacturers’ figures are way off reality; we all know how optimistic our speedos are… Dyno results are the most believable, and even they have some contradictions.

Read on to the next part where we talk about power to weight ratios…