Tuning up a 50cc engine
Xpress Internet Services
I was just wondering what I can do to tune up my 50cc scooter engine. I
noticed a poster at my local motorcycle shop advertising these fancy
exhausts which claim to give better acceleration and faster top speed. My
scooter currently accelerates promptly and has a top speed of 40-45 mph
(It'll rip the arse off any Peugeot scooter anyday - I've tried :-).
I know its a little off topic but I'm sure you guys know enough about
engines to give me some tips.
Thanks,
Bryan Lurring
PS - There's this little pink straw-like thingy hanging down from the
engine, what would that be? a breather?
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ato_zee
on flowing and polishing the ports, putting on a better exhaust,
and not really notice the difference. With cars dropping in a
bigger engine from a breakers yard really makes a difference,
though your insurers might not like it.
"Xpress Internet Services" <sa...@interxpress.net> wrote in message
news:9fbh8r$ko3$1...@news6.svr.pol.co.uk...
Guy King
from "Xpress Internet Services" <sa...@interxpress.net> contains
these words:
> PS - There's this little pink straw-like thingy hanging down from the
> engine, what would that be? a breather?
Nah...it's the willy. Would be bigger, but they wouldn't want the
riders to feel inadequate, would they.
--
Skipweasel...
Purser to URS Skip of Fools.
J.L.E
Guy King <guy....@zetnet.co.uk> wrote in message
news:200106022...@zetnet.co.uk...
> The message <9fbh8r$ko3$1...@news6.svr.pol.co.uk>
> from "Xpress Internet Services" <sa...@interxpress.net> contains
> these words:
>
>
> > PS - There's this little pink straw-like thingy hanging down from
the
> > engine, what would that be? a breather?
>
> Nah...it's the willy. Would be bigger, but they wouldn't want the
> riders to feel inadequate, would they.
>
LOL
Now-Now Guy !....
Ian Johnston
<sa...@interxpress.net> wrote:
: I was just wondering what I can do to tune up my 50cc scooter engine.
Take a day trip to France and check out a scooter shop there. They
have a huge, longstanding market in tuning up these things for fifteen
and sixteen year-olds. And with the weakenessof the Euro, prices are
probably pretty good.
Ian
--
Tim
end power on a 50cc motor, possibly the igntion timing abit too.
Anyone know if the carb can flow any more gas or is this limiting too??
Tim..
"Xpress Internet Services" <sa...@interxpress.net> wrote in message
news:9fbh8r$ko3$1...@news6.svr.pol.co.uk...
Darren Jarvis
> noticed a poster at my local motorcycle shop advertising these fancy
> exhausts which claim to give better acceleration and faster top speed. My
> scooter currently accelerates promptly and has a top speed of 40-45 mph
> (It'll rip the arse off any Peugeot scooter anyday - I've tried :-).
You may find it hard to tune up much more than it is. If it's a single
cylinder carb' fed two-stroke (which I'm almost certain it will be), then
you won't be able to alter the ignition timing, valve timing (there aren't
any!) or the fuelling much.
A better air filter and exhaust *may* make a difference, but I doubt if
you'd notice it (any improvement would be very small on a 49cc engine). If
possible, try tweaking the automatic gear system (if that's possible - I
really don't know if it is or how) so that the engine revs a little higher
before shifting up.
You could try minimising the load on the alternator (e.g. switching off
lights, etc. when not needed) and the weight of the scooter - this would
probably have more effect than anything else.
Darren
P.S.
You could try changing the tyres for some lower profile ones to give a
smaller rolling radius (better for acceleration, but at the expense of top
speed) - though this will make the speedo inaccurate and your insurance
company won't like it...
The pink tube is almost certainly a breather - possibly from the battery to
vent of hydrogen gas?
Guy King
from "Tim" <the....@btinternet.com> contains these words:
> AFAIK, it is the exhaust that posses a large restriction on the engines top
> end power on a 50cc motor, possibly the igntion timing abit too.
That was how they did them originally when the legislation first came
in, years ago. Nowadays the engines are actually quite different from
those for other markets. Things like the port timing on disc valve
engines. Yes, you're right that the carbs are also very restrictive.
It's not that easy these days to de-restrict a 50 even though the
lads will tell you that they did theirs and that it now shows 30bhp
at the back wheel and so on.
Dan
> A better air filter and exhaust *may* make a difference, but I doubt if
> you'd notice it (any improvement would be very small on a 49cc engine). If
> possible, try tweaking the automatic gear system (if that's possible - I
> really don't know if it is or how) so that the engine revs a little higher
> before shifting up.
I thought they limited these things by the design of the exhaust or intake
manifold.
Adam
Geoff Lane
wrote:
Quite an interesting thread in a ** car ** forum, I've no objections,
they all go Brmm Brmm.
Geoff Lane
Mike
wrote:
>AFAIK, it is the exhaust that posses a large restriction on the engines top
>end power on a 50cc motor, possibly the igntion timing abit too.
>
>Anyone know if the carb can flow any more gas or is this limiting too??
>
>Tim..
>
>
I think you'll find the most restrictive thing on a 50cc engine is the
50cc bit!!
Mike
Dan
> I think you'll find the most restrictive thing on a 50cc engine is the
> 50cc bit!!
I reckon a 50cc bike can go a bit faster than a 50cc moped.
Guy King
from Mike <mik...@removeme.clara.net> contains these words:
> I think you'll find the most restrictive thing on a 50cc engine is the
> 50cc bit!!
Nah, you can get 30bhp out of a 50. Racers do it all the time. On a
bike that only weighs 50kg with a tiddly rider that's a hell of a
power to weight ratio.
DervMan
> > I think you'll find the most restrictive thing on a 50cc engine is the
> > 50cc bit!!
>
> I reckon a 50cc bike can go a bit faster than a 50cc moped.
Are 50cc bikes restricted like mopeds / scooters?
The Scooter I tried was a 50cc automatic, twist and go, and it's reasonably
quick in th 0 - 15 mph range. As in, it's as quick as a car not trying so
hard, so in traffic it has adequate "junction acceleration" if that makes
sense.
Maybe you could use nitrous with it?
--
The DervMan
Anti-Spam Measures: UPGRADED Ask and you shall receive
DervMan
> > 50cc bit!!
>
> Nah, you can get 30bhp out of a 50. Racers do it all the time. On a
> bike that only weighs 50kg with a tiddly rider that's a hell of a
> power to weight ratio.
I'll say.
But surely they'll have to adjust the gearbox, and other components, to cope
with the power?
Guy King
from "DervMan" <der...@hahayoumustbejoking.goaway.co.gg> contains
these words:
> Are 50cc bikes restricted like mopeds / scooters?
Most, but not all. There's no law that says that a 50 has to be
restricted...just that certain classes of riders can't ride ones that
aren't. This has the effect of restricting just about every 50
available, since most riders move up when they are allowed to...or
they just don't care.
I'm not a small chap, but I saw a bloke far bigger than me (must have
been about 30 stone) on a tiny moped [1] the other day. It was hard
to see the bike, he just seemed to be teleporting along the A442 at
about 30mph.
[1] You know, the really tiny ones, like no more than a motorised broomstick.
mark_s.
Should have bought a restricted Aprilla RS125 instead - scooters -
okay till they hit 30/40 then they are car fodder.
Biggest laugh I've had for years on the road buying one.
Mark S.
Guy King
> >
> > Nah, you can get 30bhp out of a 50. Racers do it all the time. On a
> > bike that only weighs 50kg with a tiddly rider that's a hell of a
> > power to weight ratio.
> I'll say.
> But surely they'll have to adjust the gearbox, and other components, to cope
> with the power?
Just change the sprocket.
Shaun
<sec...@ntlworld.com> wrote:
>> I was just wondering what I can do to tune up my 50cc scooter engine. I
>> noticed a poster at my local motorcycle shop advertising these fancy
>> exhausts which claim to give better acceleration and faster top speed. My
>> scooter currently accelerates promptly and has a top speed of 40-45 mph
>> (It'll rip the arse off any Peugeot scooter anyday - I've tried :-).
>
>You may find it hard to tune up much more than it is. If it's a single
>cylinder carb' fed two-stroke (which I'm almost certain it will be), then
>you won't be able to alter the ignition timing, valve timing (there aren't
>any!) or the fuelling much.
>
Wrong.
Not only can you alter all of these of a two stroke, but you can do it
far easier and cheaper than a four stroke. The power gains are also
far greater.
Mike
<der...@hahayoumustbejoking.goaway.co.gg> wrote:
>> > I think you'll find the most restrictive thing on a 50cc engine is the
>> > 50cc bit!!
>>
>> Nah, you can get 30bhp out of a 50. Racers do it all the time. On a
>> bike that only weighs 50kg with a tiddly rider that's a hell of a
>> power to weight ratio.
>
>I'll say.
>
>But surely they'll have to adjust the gearbox, and other components, to cope
>with the power?
Not to mention be replacing pistons/barrels/cranks every 5 minutes.
Seriously, getting 30 bhp from a 50cc engine is not trivial. I have
had a go on a Honda CR125, a motocross bike with around 35-40bhp. It
felt fantastically quick, but had a power band as wide as the average
knife edge. To get this sort of power, you have to have fairly radical
port timing on a two stroke, and nice square tops to the exhaust port
to create very strong pulses in the exhaust. This *eats* piston rings
at a frighteneing rate. It also means you need an ultra close ratio
box to keep thing on the boil.
Fun, but quite wearing after a while, especially for a road bike.
However, I do know someone that had an OR50 (tiny custom style Suzuki
bike) that he modified slightly with an RD250 (air cooled) twin
engine. To say the thing was dangerously overpowered would have been
masterfull understatment, 1st gear wasn't useable, unless you liked
the front wheel going over the top of your head, and stability at any
speed > 50 mph was bad enough to worry the 500 Superbike riders. The
frame looked like it was made from drinking straws, and had
approximately the same ultimate strength.
Still, fun while it lasted, which wasn't very long. Then of course
came the twin engine 4WD Metro Turbo...
Cheers
Mike
Darren Jarvis
>
> Not only can you alter all of these of a two stroke, but you can do it
> far easier and cheaper than a four stroke. The power gains are also
> far greater.
I'd be interested to learn how - I can't see how it would be done without
replacing various parts.
Darren
Shaun
Alter the port sizes and heights with file. Does exactly the same as
buying fancy cams and heads on a four-stroke at no cost.
Altering the relative pickup location from the flywheel changes the
ignition tiiming, and the mixture is changed by plugging in a new
main jet in the carb.
All you really need to pay for is an expansion chamber exhaust which
will give a massive increase on a restricted bike.
In fact a bike that is sold elsewhere without any power or speed
restrictions usually has a simple method to keep the power down.
Removing an exhaust washer on some 125s will give 70% more power
Guy King
from "Darren Jarvis" <sec...@ntlworld.com> contains these words:
> I'd be interested to learn how - I can't see how it would be done without
> replacing various parts.
There are plenty of books on tuning 2-strokes. Mostly it consists of
removing lumps of metal from piston skirts, barrel walls and so on.
Guy King
from shaun....@spammmmm.ntlworld.com (Shaun) contains these words:
> Removing an exhaust washer on some 125s will give 70% more power
I'm not sure that's as true as it used to be. The early restricted
125s were like that, but the manufacturers got into trouble for
making it too easy to de-restrict them, so they got a bit more
cunning. That isn't to say it can't be done, just that it isn't often
that simple any more.
Andy Clews
> The message <XJdT6.9303$fs6.4...@news6-win.server.ntlworld.com>
> from "Darren Jarvis" <sec...@ntlworld.com> contains these words:
>> I'd be interested to learn how - I can't see how it would be done without
>> replacing various parts.
> There are plenty of books on tuning 2-strokes. Mostly it consists of
> removing lumps of metal from piston skirts, barrel walls and so on.
I had a book from Loose-Brain Smith (sorry, Bruce Main-Smith) with the
title "Speed and How to Obtain it" which had my ex-hippy friends laughing
their heads off. It was about tuning motorcycle engines, but only
four-strokes. The original purpose was to tune an old BSA C15 that I owned,
but the project never came to fruition. It probably would have blown up,
anyway.
--
Andy Clews University of Sussex Computing Service
(Remove DENTURES if replying by email)
Xpress Internet Services
> came the twin engine 4WD Metro Turbo...
You mean someone's actually done this?
Yours,
Bryan Lurring
mark_s.
<sa...@interxpress.net> wrote:
>> Still, fun while it lasted, which wasn't very long. Then of course
>> came the twin engine 4WD Metro Turbo...
>
>You mean someone's actually done this?
>
>Yours,
>
>Bryan Lurring
Probably but then some "fat guy" on a scooter left it for dead at the
first queue of cars at some lights........ :-)
Mark S.
Mike
<sa...@interxpress.net> wrote:
>> Still, fun while it lasted, which wasn't very long. Then of course
>> came the twin engine 4WD Metro Turbo...
>
>You mean someone's actually done this?
>
>Yours,
>
>Bryan Lurring
Oh yes!! The guy was a bit of mad man. Top bloke basically!
The clever bit was rigging up the two gear changes. Traditionaly on
Mini's this has been achived through modifiying the rear gearbox
casting to make the change rod exit through the front of the box,
towards the gearchange remote.
This guy used some windscreen wiper motors and limit switches to
effectively make a servo controlled box at the rear, controled by
micro switches on the remote gearchange.
Cheers
Mike