Yamaha TW200 2006

I'm looking at changing my rear sprocket to increase my road speed and
decrease engine rev at highway speeds. I currently have a 428 chain with
a 50 tooth sprocket. I am looking at a 428/40 sprocket. What speed
change can I expect with 10 less teeth on the rear? Will there be a
noticeable change or should I go to a 30 tooth sprocket? Anybody tried this?

 

You're probably not going to improve the TW200's "road speed" much by
fitting a different sprocket.

You don't also happen to own a Honda 350 or 360, do you?

If you *must* experiment with sprockets, change by a smaller number of
teeth, going from a 50 tooth to a 40 tooth rear will make your top
gear useless. Don't even think about putting a 30 tooth rear on there.

 

Well, they sell a 49, 48, 47, 46 etc sprocket. Does one tooth make that
much of a difference? I'll search the web and try to find out how much
this changes the gearing ratio.

 

*Boggle*

For the same road speed, your RPMs will be proportionally lower by
the new tooth count divided by the original tooth count.

So, if you are running 5000 rpm at 60 mph with a 50 tooth rear
sprocket, the new RPMs at 60 mph with a 48 tooth sprocket will be:

5000 RPM * 48T / 50T = 4800 RPM

For constant RPMs, your road speed will be speed * (50/tooth count):

60 mph * 50T / 48T = 62.5 mph

But remember, you have a 200cc single there, and it's not an unlimited
power source, as you decrease the RPMs you decrease the available
power. The folks who picked the gear ratios for that bike knew what
they were doing.

 

With the same chain pitch, a 40t vs a 50t sprocket will give you a
20% change in ratio.
Not something I would recommend either.

To calculate the gearing ratio change for various sprockets, divide
the original (50t) by the size you wish to try. e.g. 49t = 2%, 48t
= 4%, 45t = 10% ..... etc.

regards
S.O.B

 

Well in my opinion the bike should have had one lower gear for off road
and one higher gear for the highway. Or else a 2 speed rear wheel.
So now I have to get a larger sprocket for off road and a smaller one
for highway. I mean, it's ok the way it is but it could have been just a
little better.
I see a 14 tooth drive with a 50 tooth driven gives a 3.57 to 1 ratio so
1000 rpms is reduced to 280 rpms.
A 40 is 2.85 to 1 or 350 rpms, a 30 tooth is 2.1 to 1 or 460 rpms.
A 49 tooth drops to 3.5 and 280.5 rpms.

 

Thank you all.

 

Well, Broderick, you're spinning your wheels if you expect to get much
help from the trolls that hang out on Usenet. There is a TW200 forum
you can go to, and it isn't full of assholes.

http://tw200forum.com/forums/

Your rear wheel is a 180/80-14, so if you multiply 180 X 0.8 X 0.3935
+ 14, you get the rear tire diameter, which is 25.347 inches.

25.347 divided by 12 = 2.112... feet (rear tire diameter)

2.1123 X pi = 6.635... feet (rear tire circumference)

5280 divided by 6.635...=795.678...(tire revolutions per mile

Now, we have to multiply the primary drive ratio X 5th gear ratio X
final drive ratio to get the overall gear ratio.

3.318 X 0.821 X 3.57 = 9.725:1 (over all gear ratio)

Tire revolutions per mile X overall gear ratio = engine RPM at 60 mph

795.678 X 9.725 = 7738 RPM at 60 mph. Hey, that's no problem! If your
red line is 9500 RPM, why worry about it?

Yamaha knows what they are doing with their short stroke engines. Your
TW200 has a 55.7mm stroke.
55.7 X .0394 = 2.19 inches.

The formula for calculating Mean Piston Speed is Cm = .166 X stroke in
inches X RPM, so

..166 X 2.19 X 9500 = only 3453 feet per minute!

At only 3453 feet per minute, you're not hurting the engine, you'd
have to rev an engine with a 2.19 inch stroke up to 13,700 RPM to
reach the dangerous 5000 feet per minute piston speed that wears
engines out very rapidly.

Piston rings begin to flutter around 4500 RPM, they don't seal the hot
gasses above the piston top, the film of lubricating oil gets burned
off and the rings wear out quickly.

Engineers at Ducati had to turn their 998 Corsa engines at 12,000 RPM,
and the mean piston speed was around 5000 feet per minute.

The expected life span of a 998 Corsa engine used for racing was
around 30 hours.

But Yamaha's YZF600R6, with a 45 millimeter stroke can run almost
forever at a 15,000 RPM redline because the piston speed is so low.
The problem that high performance engines are running into now is
piston pin boss cracking. The rings don't flutter, the pistons crack
at 15,000 RPM.

The TW200's maximum torque is 11.1ft-lb @ 6,500 rpm. Horsepower =
(torque X rpm) divided by 5252, so your horsepower at the torque peak
is (11.1 X 6500) divided by 5252 = 13.73 horsepower.

But your engine doesn't just suddenly stop breathing at the torque
peak. The torque peak will be spread out over at least 2000 or 3000
RPM. If you work out the same formula, you get 16.351 horsepower at
7738 RPM.

If your engine is still breathing good at 9500 RPM, your engine would
be putting out around 20 horsepower. But the torque curve probably has
dropped off quite a bit by 9500 RPM.

You could retard your exhaust cam so the exhaust valves opened later
and closed later to move the peak of the torque curve to a higher RPM,
but that's a job for a really knowledgeable speed tuner.

Here are some links to look at:

http://tw200forum.com/forums/2/2954/ShowPost.aspx
MORE SPROCKET OPTIONS !!!

http://tw200forum.com/search/SearchResults.aspx?q=primary drive&f=&u=
RPM and Speed calculator


http://www.totalmotorcycle.com/photos/2006models/2006models-Yamaha-TW200.htm

http://www.cycleworld.com/article.asp?
section_id=12&article_id=128&page_number=3

 

Not familiar with your particular model of bike but in many cases it would
be quicker, easier and cheaper to change the front sprocket.....up one
tooth. Often there is enough adjustment available so that you don't have to
change the chain either.

 

I don't have a tach on it. It red lines at 55mph. That's why I want the
higher gear ratio for the road so I can cruise at least 65 or 70 without
having the piston fly out of it.

 

How do you know the engine is reaching the red line, if you don't have
a tachometer?

The piston is NOT going to fly out of the engine. I explained to you
that you have a short stroke motor that has very low piston speed.

Are you sure you're getting into 5th gear? One time I took a Yamaha
dirtbike motor apart to overhaul it, and I saw that the circlips that
located some of the gears were kind of sloppy. But I didn't feel like
going down to the dealership and buying new circlips. When I raced the
motorcycle in the desert, everybody passed me because I couldn't shift
into 5th gear.

Count your shifts 1 > 2 > 3 > 4 > 5. You should shift four times to
get into 5th gear.

5th gear has a 0.821:1 ratio. That's overdrive in a motorcycle
transmission.

Go to this website: http://www.650ccnd.com/calc.htm

The default numbers are for a V-Star 650, you have to use these
numbers in the yellow boxes:

Primary reduction............3.318

1st gear is........................2.833

2nd gear is......................1.789

3rd gear is.......................1.318

4th gear is.......................1.040

5th gear is.......................0.821

final drive w/stock gearing is...rear 50 divided by front 14 = 3.571

rear tire diameter..............25.347 inches

If you type 6500 in the top of the first box, and hit the recalculate
button at the bottom,

1st gear speed is 14.6 mph

2nd gear speed is 23.1 mph

3rd gear speed is 31.4 mph

4th gear speed is 39.8 mph

5th gear speed is is 50.4 mph

If you use 8000 as your maximum RPM, and recalculate,

1st gear speed is 18 mph

2nd gear speed is 28.5 mph

3rd gear speed is 38.6 mph

4th gear speed is 49.0 mph

5th gear speed is is 62.0 mph

And, if you want to rev your engine up to the 9500 RPM red line (which
won't hurt the engine, you can cruise at redline all day if you check
your engine oil frequently),

1st gear speed is 21.3 mph

2nd gear speed is 33.8 mph

3rd gear speed is 45.9 mph

4th gear speed is 58.1 mph

5th gear speed is is 73.7 mph

 

Um, this isn't the greatest advice in the world. Sure, revving to the
redline won't harm an engine, but running it flat out all the time will
wear it out rather faster than it would normally, oil changes or no oil
changes.

Not the best thing to tell a newbie.

 

Oh, FSS! This is the 21st century, we're talking about a modern
motorcycle, not some 1966 CB-160.

The short stroke, oversquare TW200 is designed to run at high RPM
continuously, and it has to run continuously at greater than 6500 RPM
to produce the 16 or 17 horsepower necessary to cruise at 68 mph. It
only produces about 13 horsepower at the torque peak of 6500 RPM.

The old rule of thumb of one more tooth on the front sprocket or three
less teeth on the rear sprocket WILL NOT WORK because of the 26%
overdrive fifth gear.

He would have to drop six teeth and install a 44 tooth rear sprocket
to get gearing that reduces RPM by 13.6%. Then he'd be able to reach
about 68 mph, on the flat, with no headwinds at around 7400 RPM in
fifth gear.

But the 26% RPM drop between fourth and fifth gears means that he will
have to rev the engine to around 8500 RPM to avoid bogging it down on
the shift and having to go back to fourth gear.

Why go through all that crap, if the engine is designed for cruising
at 9500 RPM redline?

The whole idea of horsepower production is that you repeat the
operating cycle as often as possible. That translates into: "to get
the horsepower you need, you have to run the engine at the highest RPM
it can stand."

The newby will get the high speed cruising he wants without buying any
new sprockets at all, if he just learns to appreciate his engine in
the way that it needs to be appreciated, i.e., at the higher RPM it
was designed to cruise at.

Personally, I wouldn't recommend riding at highway speeds on those
knobbly tires, though...

 

And this is you speaking! Wow.

Fair enough.

Because that's not what "cruising" is. 9500rpm is maximum revs, and
running *any* engine flat out all the time will wear it out faster
than if one ran it for some (any) of the time at lower revs. This is
basic common sense, and is the point I am making. The engine is
designed to run at that speed without the valves bouncing into the
pistons, sure.

You claim a (semi) aeronautical background, don't you? Why do you
think aircraft have "maximum" and "cruising" speeds quoted?

Because (fanfare of trumpets): there's a difference!

Let me get this absolutely straight: are you seriously saying that
running an engine at max revs all the time will result in a shorter
engine life, compared with a lump run at lower revs? Be very careful
how you answer.

 

On 18 Apr, 11:03, ,

Heh. There should be a 'not' in there somewhere, obviously.

 

Yes, this is me, trying to adjust your point of view to the technology
of the late 20th/early 21st century.

OK, in order to move the vehicle through the atmosphere, the available
rear wheel thrust has to match the total aerodynamic drag
plus rolling resistance plus whatever work is encountered in raisng
the vehicle from one elevation to another.

I'm not going through all the math just to prove a point to a
professional skeptic like you.

The engine belongs to the owner, he gets to decide how he will treat
it. Frequently taking the RPM to the red zone is expected with small
displacement engines whose development was based upon the displacement
limits of the FIM.

Anybody who doesn't believe in using the powerband of a small
displacement engine and shifting gears to keep the engine in the
powerband should be riding a H*****y D******n.

Some concerned riders asked Honda about the meaning of the red zone on
their tachometers back in the early 1980's. Honda told them what I am
telling the newbie: you can run at the red zone as long as you want,
just keep an eye on the oil level and change oil frequently.

Modern Japanese engine development has certainly been concerned with
reducing the weight of the valves, using lighter valve springs, etc.,
but the real barrier to achieving high RPM in the 1960's was the
development of thin, low mass piston rings that wouldn't flutter
at high RPM.

On the recommendation of the part$ guy at the Yamondakawazuki dealer,
I bought a set of thin ringed Wiseco pistons back in 1967 to use in my
Yamaha 250 that had the TD-1B top end and carburetors. I couldn't
evaluate the performance of the piston rings because I
didn't understand what piston ring flutter was all about.

And I had also done the piston crown and skirt modifications that
everybody was doing because the magazines said that was what the
racers were doing.

Some very famous racers (whose sons and grandsons are now famous
racers) were out at Willow Springs, sawing part of the piston skirt
off with a hacksaw, because *somebody else* told them that was the
path to more power. The guy holding the piston because they had no
vise suddenly yelped, "Hey! That's *my thumb* you're cutting there!"

And the beat goes on. There is a reservoir of experiential wisdom that
trickles down to the newbies, and they pass it on, just as if they
understand it.

The OP is worried about his piston flying out of the motor at high
RPM. Where did *that* idea come from? Did it originate with H*****y
D******n owners that feared being emasculated by the engine that was
directly under their balls?

Probably.

Oh, so you want to compare apples and oranges? I have knowledge and
experience with both motorcycles and airplanes.

There are colored bands on an aircraft's airspeed indicator. The white
arc indicates the upper and lower range of speeds for extending the
flaps. The lower end of the white arc indicates the power-off stall
speed in the "dirty" configuration.

And, if you extend the flaps at a speed beyond the upper range, get
ready for the aircraft's nose to drop. You will not like this
situation as the aircraft heads for the ground. You probably won't
have enough elevator trim to compensate.

Throttle back! Retract your flaps!

And, the same thing will happen if you manage to extend the landing
gear at high speed.

The green arc defines the normal operating speed range. The low end of
the green band is the power off stall speed in the "clean
configuration". The upper end of the green arc is the maximum
*structural* cruising speed for normal operations.

The yellow arc is the caution zone. Don't fly in the yellow zone
except in smooth air.

The red line on the airspeed indicator is the Velocity Never Exceed
speed. This is the maximum speed for flying in smooth air.

But, never forget that the indicated air speed is not the same as
calibrated airspeed, especially if you make a habit of flying above
25,000 feet, where the air is less dense and the stall speed increases
well into the white arc. And the lower air density means that
pilots of older aircraft with NACA airfoils can run into the same
compressibility problems that terrified P-38 pilots during WW2.

Another very important speed is not marked on the airspeed indicator.
It's the critical maneuvering speed, which is the maximum speed at
which the pilot may fully deflect the control surfaces without
permanently damaging the aircraft structure. This speed can be found
on placards, the pilot's handbook, or the flight operating manual.

Slow down for maneuvers, the wings will only bend so far, then they
won't spring back...

Now, what were you going to say?

How dramatic. Yawn...

Everything mechanical wears out, if somebody uses it. It's the
newbie's motorcycle. He can decide how fast he wants to use up its
limited lifespan.

Be careful what you post without proof reading it first.

 

Yes, but that's not the same as running it flat out *all the time*, is
it?

Oh dear....

Ah. Precisely. Which will be more limited if he follows your "advice"

So, once again, we have incorrect advice, covered by a follow-up of
irrelevancy which you hope will divert people away from your original
imbecility...

Simple fact - running engines flat out all the time will make them
wear out faster. It is not good advice to tell people to do this.

 

Do you even know what a TW200 is? Cycle World described it as a quad
with two wheels. The TW200 is meant for off road riding in loose
terrain, so it has big wide tires that are nevertheless DOT approved,
and it has an overdrive 5th gear so the dirt donks can ride on the
highway from home to the riding area and back.

The OP is dissatisfied with his perception that his engine is turning
too many RPM at the cruising speed he desires. He doesn't understand
that he's not hurting the engine by cruising at redline, and I'm
advising *him* that the engine is designed to run continuously at red
line, but you just want to argue.

As per your usual practice.

Next you'll be calling me "Shirley".

What's the matter? No aeronautical background to back up your
argument? The difference between cruising speed and VNe is related to
maintaining the structural intregity of the aircraft. Once bent, the
structure does not spring back to it's original shape.

However, there are also fuel economy concerns. A motor vehicle running
at top speed on the ground doesn't have to expend fuel to generate
*lift* to support it, the surface it's running on supports it.

But the pilot of the aircraft has to trim the elevator to a slight
nose down attitude to minimize induced drag. He then gets the needed
lift
by the fact that lift is directly proportional to (velocity^2 of the
aircraft in knots X coefficient of lift X wing area X pressure ratio)
divided by the bulk constant 295

And, a single engine general aviation aircraft equipped with a
Continental or Lycoming engine will be burning about 8 gallons of 100
octane low leaded fuel every hour of ooperation, even when the pilot
throttles back to 80% and leans out the mixture.

Rotax makes a small flat four-cylinder engine that comes normally
aspirated or turbocharged. The unaspirated Rotax 912 displaces
1211.2 cc's and produces 80 horsepower at 5500 RPM. Throttle back to
75%, it burns 4.5 gallons of pump gasoline.

By comparison, the OP's TW200 would probably get about 60+ mpg running
at redline, so he would only burn 1 gallon per hour---if he spent an
hour on the road, instead of dirt donking in the hills.

It's his choice, not yours.

Are you keeping a list of your disagreements with me? Have you been
writing scripts for plays, while singing "Mr. Brownstone"?

Running his TW200 at maximum speed on the highway is not that great an
idea. Yamaha has included an overdrive 5th gear in the transmission
for those highway commutes, but the OP doesn't understand the design
and intended use of the motorcycle and he wants to change it, without
understanding the physics and math involved.

I explained those ideas, but you still want to debate with *words* and
generalities about what's economical or prudent, as has been your
previous strategy.

Give it up. You're NOT going to change my point of view.

 

Yes. And you are saying it is fine to run the engine flat out,
endlessly.

And I am saying that while these are safe revs, running an engine at
maxiumum revs will wear it out faster.

Now this is simple, but then so is your mind. I don't know how to make
it any simpler.

You will not find anyone on this forum, or anywhere else, who will
disagree with my very simple statement.

 

You're the one who needs support, not me. Have you finished with the
script for "Mr. Brownstone" yet?