Sprockets & Torque & Cruising Speed & MPG & Chains

I could use a brief refresher course on changing sprockets on a
motorcycle. With a dual purpose bike I once had, when going off-road,
I simply lengthened the chain and hung it around a larger rear
sprocket. Guess I had a "dual" sprocket on the back of that bike.

On the TW200 I thinking of buying, I understand it comes with a stock
14 front sprocket and a stock 50 or 52 rear. And since I've clearly
stated many times that its use will primarily be ON-ROAD, I intend to
switch out the tires to the TW203 and TW204 plus perhaps some sprocket
changes.

1--What will be the performance results of changing the front to a 15
or even a 12?

2--What will be the performance results of changing the rear to a 47
or a 42 or even a 55?

3--By performance results I mean mpg, shift points, higher speed and
quieter engine operation, etc.

4--Is there a publication and/or online source that would provide in-
depth info into sprocket modifications on motorcycles?

Thanx,

Bill

PS--When ordering an aftermarket sprocket, do you need to order a new
chain with it?

 

For Christ's sake, leave it as standard. It's got sod all power
anyway, really, and gearing it up will be a waste of time on-road, and
gearing it down will make it snappier on-road (and more useful off-
road) but thirstier.

Your proposed gearing changes on the front sprocket are daft: I doubt
whether it's really got the power to pull top gear with a 15T
sprocket, and 12 is way too low, plus it'll wear out the sprocket
really fast.

Your rear sprocket changes are even dafter. A 42-tooth rear sprocket
with a 14-tooth standard front will give a gearing of exactly 3:1, and
no way on God's earth will it pull it. Think - what happens when you
go up a hill in a car, on a bicycle, or anything in a high gear? It
slows down. Why should a motorcycle be any different?

If a TW200 manages to pull, say, 75mph on the flat on stock gearing,
then worst case (your biggest sprocket on the front and smallest on
the rear) will gear it up to do 100mph or something (I can't be arsed
to work out the calculations right now). *It won't pull it*.

Effect on mpg is likely to be poor whatever you do: gearing it down
means it'll be revving higher: gearing it up (unless it's geared
abnormally low in the first place) won't improve things as you'll be
holding the throttle wider open to get the poor thing to pull.

As for whether you need a new chain: well, if you add or subtract
sprocket teeth, it doesn't take rocket science to work out what will
happen to the length of the chain run.

Jesus, just leave it alone. Ride it first, and then decide whether the
gearing needs to be fucked about with. Generally, however, you'll find
that the manufacturer knows much better than you do. Do you really,
really think that Mr Yamaha will get the gearing out by as much as 25%?
[1]

[1] seat-of-pants figure taking your most wild sprocket extremes

 

All the gear ratios and tires sizes for the TW200 are available
online. Look 'em up and plug them into this calculator.

http://www.650ccnd.com/calc.htm

It's best to run new chain on new sprockets.

We discussed the subject of re-gearing the TW200 extensively about a
year ago with a guy who wanted to believe what he wanted to believe,
that he would get phenomenal mileage without performance degradation.

He's still around, with a name change, claiming that installing a
smaller rear sprocket gives him better mileage and that he doesn't
have to downshift for every little hill or headwind...

But, if you study the TW200's gear ratios, you will see that they are
not all equally spaced, they get closer and closer together as you
shift up.

This indicates that the TW200 really doesn't have a lot of surplus
power to allow
gearing it up very much.

I wouldn't recommended raising the overall gearing more than about 3%
or 4% if you don't want to spend a lot of time riding one gear lower
than high gear.

 

Now *there's* a useful link.

Um, that's not the real point. The point is that by messing with the
sprockets he's altering the chain run length.

Exactly.

 

chain with it?

I already realized a different sprocket would require a different
chain length. On my old trail bike I use to add a small section of
chain when changing to the larger off-road sprocket and pop it out
when reverting back. My question was more of a "understood" comment
sorta like it's a good idea to change the oil filter when you change
the oil or both wiper blades when one goes bad. With any project,
it's always best to have all the components start out equally new.

Bill

 

Jesus. Not one master link in a chain, but *two*.

Look, it's a shit idea, so forget it.

 

We've been through all that in another thread. This bod wants to buy a
TW, and then, basically, **** it up.

 

OK. Carry on, that man.

 

One problem with that. I don''t want an XT225 and last time I checked,
anyone, with his own fucking money, can buy any fucking motorcycle he
wants and have it modified any fucking way he wants. Is that concept
too deep for some of you old fuckers who can't stand change or someone
having a different opinion than yours?

TW, and then, basically, **** it up.

No, you pompous bag of hot air with the personality quotient of a
dried dog turd, not **** it up, simply modify to my liking. Yasee,
you old shithead, lots of guys modify motorcycles, scooters, etc.. At
least guys younger than 125, which would obviously leave you out of
the mix. Gawd, you are one funny and weird old fucker. You don't
have a clue about 2008, you're still locked in some 60's time warp or
earlier.

Any other fucking questions from you mindless fuckheads?
HAHAHAHAHAHAHAHAHAHAHAHAHAHA

Bill

 

over Uncle Jay's computer.

Your little so-called "baiting" routine doesn't work. You and the
dumbass TOG just make me laugh with your silliness and stupidity about
the real world.

Bill
(Who appreciates all of the little silly-ass comebacks from the silly-
ass group including silly-ass TOG and silly-ass Geyser. Thank you
boys, keep those silly-ass comments coming. They're a riot. All of
us here get a chuckle reading the responses from the OFC (Old
Fuckheads Club).

<SNICKER> <HAWHAWHAW> <SPEWWWWWWWWWWWWW.......>

 

I dunno. It seems to be working fine, from where I sit.

 

By raising the gearing by 20% or more? That's not modifying: that's
really fucking it up.f

Yasee,

Ah, right, rattle in orbit again. Excellent.

 

And, as usual, from where you sit, most everything is wrong.
Especially since you spend most of your time sitting on your brain.
You said it all TOG BUTT with your first two words "I dunno." And you
probably haven't known shit since the day you were born. HAWHAWHAW

Bill

(Still enjoying lots of laughter as I observe the old fools who
continue to come back and dance for me. Who's baiting who TOG BUTT??
HAHAHA YOU are the dipwads getting baited in these exchanges but
you're too fucking stupid to realize it).

 

Not all all. Guess what TOG BUTT, despite how this fact will no doubt
crush your fragile and inflated ego, the truth is "You don't know
everything and you are dead ass wrong in your latest assumption." I
have talked with a couple of techs and told them some of the brainless
statements you've come up with and their usual response is "What is
the guy, a dumb-assed newbie in the cycle world?"

Basically, buttbrain, you're done. Your advice sucks, your brain has
quit functioning, your attitude sucks and you also probably put on
your pink dress, the one you were wearing in that photo, and suck
anything that walks by. You're pitiful old man. Just call Dr.
Kevorkian and be done with it. You're useless as dog piss on a clean
carpet. LOLOLOL

Bill

 

So either learn to read the gist of an OP before you answer or people
will think your name fits you perfectly, since a "geyser" is something
that spews out a lot of hot steam, etc and in your case just spews out
a lot of useless shit.

The reason I quoted all of those sprocket sizes was those were the
figures I got from others, they weren't my idea. You see, the purpose
of the post was to get some help from the alleged "experts" on this
group about choosing the right sprocket to meet the objective I had in
mind---i.e. better mileage, quieter top speed operation, less shifting
in the lower ranges, etc. IOW, making it more of a road bike than a
trail bike. So what happens---the typical responses from the typical
know-it-all fuckheads like that asshole TOG and a couple of others.

They, and perhaps you, have no concept of how to actually help anyone,
they only exist to spew forth their personal, mindless opinions and
whether or not they have anything to do with the post seems to be
immaterial.

It's what you find on many newsgroup, the pompous, egocentric
dickheads who don't know shit so they try to hide it by just
denigrating the OP and his ideas.

So piss off, Geyser, and take TOG BUTT with you. Neither of you have
anything valid to offer on this subject (or most of them on the
newsgroup) anyway and you're just taking up bandwith with your
bullshit. Besides, if you post again, it just provides more fodder
for the good laughs we all get here from reading your crap. Leave the
help to those who can actually provide it.

Bill

Actually, I take that back...you and TOG ASS continue to respond.
Laughing at you has become a regular recreational activity around
here. HAHAHAHA

 

No, he doesn't, as he's not even got the bike yet, and the gearing
variations he is proposing are, at their extrmes, totally impractical.

Bike makers have whole departments dedicated to working out the
gearing for thair machines. They don't *always* get it right: my own
K1100LT is geared a bit too low in top, for a tourer, and my old
Triumph 1200 Trophy was geared slightly too high. But by and large,
correct gearing is more honoured in the observance than the breach[1].

And he (or his 'expert' friends) is suggesting a possible combination
of a 15-tooth front sprocket and a 42 rear (stock: 14/52). Or, at the
low extreme, 12/55. There's no way the bike will pull the former and
with the second, it'll be screaming its head off.

If he wants to mess about with it, he should ride it, note down the
rev/gear figures, see how many revs it's pulling flat out in top, and
work from there. He might want to make a very small change, but until
he rides the little whizzbang, there's little point in asking. And
*no* point in asking about such daft sprocket sizes.

[1] He'll have to look that inverted reference up.

 

To get these things you would likely want to add teeth in
the rear sprocket only. This makes the engine turn slower at
the same road speed, which will give you these things.

But, the tradeoff is your accelleration will drop.

I'm going to assume you want the better mpg because you
want to commute long distances on a highway. The reason
is that if your only going to be riding very short distances,
your only maybe buying a tank of gas every month, so who
the hell cares about mpg?

Now, do you really want to be merging into highway traffic
going 70mph from a freeway entrance ramp, on a bike that
has compromised accelleration? Are you trying to get rear-ended?

This is why people are saying this is a stupid idea. Your
likely to get yourself killed.

And as for 2 master links, that is also a stupid idea on a
cruiser, unless your goal is to have the chain break and
get wrapped around the rear sprocket and jam the rear
wheel - at 70Mph on the same freeway.

Ted

 

mind---i.e. better mileage, quieter top speed operation, less shifting
in the lower ranges, etc.

Okay, add teeth to rear sprocket only. Advice was what I was looking
for, not denigration and criticism. Thank you. And I realize
acceleration will drop.

the hell cares about mpg?

Your assumption is correct and so the second sentence will be ignored
since it's inapplicable. The commute is approximately 1500 miles per
month, about 70 miles round-trip every weekday and is over flat
secondary paved backroads where I'll be traveling between 45 and 55
mph most of the time.

No, and my previous response also renders those two questions
inapplicable.

No, people are saying it's a stupid idea for no valid reason at all
except just to lord their so-called knowledge over someone without
paying any attention to the uniques situation posed by the poster.
It's common for the pompous know-it-all freaks like TOG to do that.
They're so wrapped up in their own opinions, they cannot see how
someone else's situation could differ and how their ideas would be
inapplicable to that situation. Sorta like you ASSUMING about the
freeway and ASSUMING that it was a stupid idea because I could get
myself killed. Both inapplicable to MY situation, maybe not others.

Where do I start with the assumptions and inaccuracies?

1--I never said anything about two master links. I believe that was
stated by a responder to my post.

2--It is not a "cruiser," it's a dual sport bike (TW200).

3--70 mph on the freeway? No freeways involved and I wouldn't ride
that bike 70 mph anywhere and I doubt it would even go that fast with
my weight and what I would carry to work in a container on the back.

But Ted, once we sifted out all the assumptions, at least you helped
with the choice of the rear sprocket. And that's the idea of
responding to posts. Analyzing exactly what is proposed, assuming
NOTHING and then offer sound advice on the SPECIFICS of the post.

Bill

 

Just another useless, no-help, pompous response from the Chief Asshole
of Reeky, the know-nothing sack of dogshit called The Older Gasbag
Gentleman. And YOU are the only thing that is daft, you ignorant old
fucker.

 

Gong! A rear sprocket with more teeth causes the engine to turn FASTER
at the same highway speed, increasing overall torque multiplication,
enhancing acceleration, and *possibly* causing the engine to burn more
fuel.

The typical performance rider *wants* more acceleration and is willing
to give up some top speed to get a little more *apparent power* off
the line, so he will either
install a front sprocket with ONE less tooth, or a rear sprocket with
THREE more teeth.

This change typically drops the overall gear reduction about 7.5% and
that's all that is practical. If he changes the overall gear reduction
by, say 15%, that will effectively make his 5th gear into a 4th gear,
and he's always going to be trying to upshift one more gear to reduce
cruising RPM.

OTOH, the OP wants to reduce cruising RPM and enhance mileage, so he
would
install a rear sprocket with as many as THREE teeth LESS.

The TW200 has a red mark on the speedometer at 55 mph, and this has
fooled at least one rider into thinking that the engine is wound up
tight at only 55, but the
TW200 will go faster than that, as has been discussed on the TW200
owner's forum.

Installing a rear sprocket with with more than three teeth less than
stock would result in the rider having to downshift for every slight
hill or a headwind.