Stupid Question Time

General scooter chat, any scooter related non technical info.
MightyGem
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Sat Aug 04, 2018 9:34 pm

An Li 150 will do 45mph at X number of revs.

Convert said scooter to 175, but keep the original gearbox. At 45mph it will still be at X number of revs.

Correct?

Muppet
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Sat Aug 04, 2018 9:41 pm

MightyGem wrote:
Sat Aug 04, 2018 9:34 pm
An Li 150 will do 45mph at X number of revs.

Convert said scooter to 175, but keep the original gearbox. At 45mph it will still be at X number of revs.

Correct?
is right
im not a complete idiot
.
.
s me of the piec s are mis i g

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coaster
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Sun Aug 05, 2018 9:50 am

+1, if the revs stay the same and the gearing is the same then the speed will not be affected BUT the engine will produce more power and might be able to get to those revs quicker and might be able to sustain that sped up hill. With other tuning mods like a better exhaust, it might rev higher and THEN it will be going faster.

Hope that makes sense, its a bit like riding a push bike along a flat road at a steady speed in top gear. If you want to faster you have to pedal faster. You could spend a couple of months going t the Gym building up your quads and then jumping on the bike again but if you spin the pedals at the same rate as before you will not be going any faster but would find it easier on the hills.

wrecklessrobbie
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Sun Aug 05, 2018 9:44 pm

I know im gonna sound like a right knob asking this.. :oops:
I have a series 3. It was a 150. I changed it to 175.
Why does the extra 25cc make it go faster. Is it the above reason you have mentioned coaster.
When ever i think of lambrettas the piston goes up and down. Turns the crank, turns the front sprocket, turns the clutch and gears and into the wheels.
So most parts are the same.
I know if you alter the front and clutch sprocket it alters the gearing and so makes higher speed.
Does the extra 25cc just make it easier. Cause if it revs the same as either a 175 or 150...why?
Sorry for asking ill get my coat ...

wintermod65
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Mon Aug 06, 2018 11:55 am

Ill add to the stupid questions

why when there are numerous tech sections on here do people persist on asking tech questions in the general chat section ??? .

does the inability to choose the correct place where to put things affect other areas of your life , do you find you go in the opposites sexes toilet for instance .

im beginning to think it must be the inhalation of two stroke that affects the brain, maybe the peculiar habits associated with classic scooter riders will cease when we're all on GTS' or Sconasties!!!!

MightyGem
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Tue Aug 07, 2018 9:12 pm

wintermod65 wrote:
Mon Aug 06, 2018 11:55 am
Ill add to the stupid questions

why when there are numerous tech sections on here do people persist on asking tech questions in the general chat section ??? .

does the inability to choose the correct place where to put things affect other areas of your life , do you find you go in the opposites sexes toilet for instance .

im beginning to think it must be the inhalation of two stroke that affects the brain, maybe the peculiar habits associated with classic scooter riders will cease when we're all on GTS' or Sconasties!!!!
Oh dear. :roll:

I was just having a general chat. That's why.

To the rest of you: thanks. That what I always thought, but someone seemed surprised when I said so,

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diesel
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Tue Aug 07, 2018 9:52 pm

I agree MightyGem, its a general interest question, as appropriate here as anywhere else.

hendy
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Tue Aug 07, 2018 10:17 pm

Assuming the tune of the 150 and 175 are identical, the 175 will produce 1/6 more torque as the explosion is acting on a 1/6 larger surface area. Therefore at peak rpm for the 150, the 175 has just a bit more power so it can push through the air just a wee bit faster and the rpm will rise to achieve that. Power = torque per second as torque is the same thing as energy.

This is a little bit of a simplification, but it's the nuts of it.

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EddieStone
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Wed Aug 08, 2018 11:06 am

Increasing the capcity increases the power (admittedly by not much). If the cylinder is turned for more power, this is more effective doing it on a 175 than a 150. IF you increase the power sufficiently you can increase the front sprocket a tooth (or more depending on the power produced) and then you will be going faster at a given rpm.

Increasing the power produced by the engine will increase acceleration. Increasing the power sufficiently that you can increase the gearing will increase your speed at a given rpm.

Increasing from 150 to 175 also helps when carrying a pillion or luggage, battling a headwind, a hill or another scooter...

wrecklessrobbie
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Wed Aug 08, 2018 6:27 pm

Ah...if im reading that right then.
More volume or cubic capacity will give more explosion in the cylinder allowing the revs to rise quicker. Which means it has more torque.
Enabling you to alter sprockets if so desired.
Also if you open up ports etc it helps even more.
Thank you for the simplified reply.
I always wondered and never dared ask. :oops:
Errr never meant to upset anyone by asking here. But i presume this is the same for both Lambrettas, Vespas and any other 2 strokes.

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