MZ Moskito SX Performance Questions
Timothy Jones
I have a Moskito SX (49cc, air cooled, 2stroke) and wanted to mod it and try
and get some more speed out of it. I use to mainly to drive to school, but
the new place I live in has some big hills and a 45mph speed limit on the
road to school. On flat ground I get about 40-43mph, but I wanted to
increase it atleast to 50mph, or maybe even 55 so the people in cars dont
try to kill me. The local shop I got it from said I should look into a 70cc
cylinder, exhaust, and a carb. Anybody know what kind of power increase that
will yield? And any brand of parts that I should be wary of? The shop would
install those 3 parts, and a new belt for $500, although they never said
what cylinder,exhaust,carb they were going to put in.
Also I have noticed when I am riding, once a week or so, at full throttle
the bike will all of a sudden get really bogged down and the more gas I give
it the more it feels like its going to die. I've had to pull off the road
before because of this. After I back off the throttle, about 5 seconds or
so, it will be back to normal, and I can speed back up. I've replaced the
plug, and tried getting gas from a different station. Still have the same
problem. Perhaps the fuel filter? I'm not really sure, any ideas would be
great.
Thanks in advance for the time,
Tim
Dave Wood
a Zuma or Vino. Check out the Moskito Classico. If that's not a Vino with an
MZ badge, I don't know what else it'd be. MZ and Yamah are strategic
partners and I know their streetbikes use Yamaha engines so I assume the
cooperation extends to scooters.
If so, the parts will likely be Malossi or Polini. They make most of
the big bore kits and such out there for small scooters and 50cc dirtbikes.
The Polini website shows 68cc big-bore kits for the Zuma that claim between
9.5hp@ 6000 rpm to 10.8 hp @13,500 rpm.
They also have carb. kits, reed valve blocks, exhausts pipes and variator
"speed pulleys".
www.polini.com The Malossi site www.malossi.com also has big bore kits,
variators and electronic control modules for the Zuma. What I like about the
Malossi site is that they have downloadable assembly instructions for their
products. One thing that is usual when going to a big bore kit is to get a
different variator front pulley. This allows for a higher top speed at the
same rpm as the stock engine, using the bigger displacement to keep the
acceleration up.
We have a malossi big bore kit and variator in my wifes People 50. With
the stock carb. and pipe - no rejetting was necessary - it went from a 45
mph indicated top speed to burying the speedo at 50+ mph (the highest
marking on the speedo). I estimate 55mph. The difference was very
impressive - it accelerates better and has a higher top speed. The only
thing is that it still bogs on big hills, though not as bad as stock.
I've seen people with fully kitted bikes claim 65 mph top speeds but I
don't know what the reliability is like.
As for the bogging at high speed, it could be the fuel filter or other
obstruction (kinked fuel line etc.). It might also be a "soft" seize" -
which is bad. I believe that someone on the newsgroup said that the Zuma has
a rev limiter - your MZ might too but you shouldn't have to pull off the
road, just slow down a bit.
-Dave
"Timothy Jones" <jon...@cfl.rr.com> wrote in message
news:01Vlc.559449$Po1.5...@twister.tampabay.rr.com...
Dennis Lee Bieber
declaimed the following in alt.scooter:
> Also I have noticed when I am riding, once a week or so, at full throttle
> the bike will all of a sudden get really bogged down and the more gas I give
> it the more it feels like its going to die. I've had to pull off the road
I'd suspect mixture -- though whether too lean or two rich I
can't say.
> plug, and tried getting gas from a different station. Still have the same
Did you examine the spark plug when you took it out? Be nicest
if you could take it out when the problem appears <G> If it looked wet,
rich mixture flooding the engine. Ash build-ups?
--
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Dennis Lee Bieber
declaimed the following in alt.scooter:
> which is bad. I believe that someone on the newsgroup said that the Zuma has
> a rev limiter - your MZ might too but you shouldn't have to pull off the
> road, just slow down a bit.
I hadn't even considered that -- it's been almost 20 years since
I drove a car with an over-rev governor... And that was a pain (94hp,
vehicle weight 2400lbs)... I'd pull out of a truck stop and onto the
freeway -- and since I "properly" use the merge lane to match speeds
with traffic I often bounced red-line in first or second... Only to have
the engine cut-out forcing me to drift to the shoulder until it reached
idle and stabilized again.
Mike Lynch
fuel can get to the carb as you are using it faster
than it can be replaced.
Check for a slight blockage. You must do this if you
are going to fit a performance kit as it will use far more
gas than the standard motor.
Mike.
"Timothy Jones" <jon...@cfl.rr.com> wrote in message
news:01Vlc.559449$Po1.5...@twister.tampabay.rr.com...
Timothy Jones
This might help diagnose the problem as well. I forgot to include it. The
problem with the bogging down is very similar to when I first start the
scooter. If I don't let it idle for 30 seconds or so, letting it "warm up",
when I give it gas it will bogg down and sound as if it is going to die. And
if I give it enough gas, it will die. Although I don't always have to let it
warm up like that. Some days, its good to go as soon as I start it. I live
in Florida, so I don't think its actually a temperature thing (warming it
up). For that reason it doesn't seem, to me, that it would be a rev limiter
unless I have two different problems, one when I start it and one when I'm
riding at full throttle.
Also I found a Yahoo group (
http://autos.groups.yahoo.com/group/MoZkito_Scooters/ ), that deals with the
moskito scooter and as Dave pointed out, they do use the same Yamaha engine
as the Vino, produced by CDI. I was thinking of getting this performace
upgrade kit, its for the Vino but I just emailed them to find out if they
think it would work with mine.
http://www.provoscooter.com/shop/product_info.php?cPath=21&products_id=65
What do you all think? Should that get the job done, and are they good
parts?
Thanks again,
Tim
Dave Wood
If the problem persists, it sounds like a fuel mixture problem. The starting
problem you have may well be temperature related but not in the way you
think. Cooler air is denser so on cool days you'll get more air flow for a
given amount of fuel and vice versa on a warm day. The difference isn't
great but it is noticeable - two stroke engines are more sensitive to
jetting than 4 strokes. If you have some borderline condition already, you
may have a jetting problem. Unusual conditions might be living at a very
high or very low altitude or in an unusually hot or cold climate. Even
relative humidity can have an effect. Modern 2 strokes tend to be jetted on
the lean side to meet emissions requirements and most scooters can benefit
from slightly richening the mixture.
As Dennis suggested, a look at the plug can be in order. The way to do a
"plug chop" is to find a road where you can safely run at full throttle for
an extended period of time (say 30 seconds or so), turn the engine off
using the kill switch, immediately close the throttle, coast to a stop (out
of traffic) and pull out the plug. You should be able to find a plug reading
guide on line or in the back of most any Chilton's manual but in general,
heavy soot deposits or wet/oily plugs are signs of too rich operation. Lean
is harder to describe but small black balls on the porcelain are signs of
being seriously lean.
If the mixture looks off, you'll have to fix it. Some things that can cause
lean running are: loose carb. boots, missing vacuum port plugs, misadjusted
float level in the carb, main seal leakage on 2 strokes (bad). etc. A very
dirty air filter can cause rich running. Some ignition problems can also
cause bad running and look like mixture problems - timing too far off
(advanced or retarded), worn, fouled or poorly gapped plugs, the wrong heat
range plug etc. The symptoms of most of these scenarios are very similar and
can be tough to sort out.
However, your symptoms sound most like a fuel restriction and you should
check that first. Then make sure it is tuned up to factory specs - the right
plug, cleaned and gapped correctly, clean air filter, timing set correctly.
Then investigate for air leaks. Then check the float level setting in the
carb. and the condition of the float and needle valve. If your scooter is
new enough to be under warranty, I'd have the dealer check it.
Regarding the http://www.provoscooter.com website, it is a pretty cool site
and $470 for the stage 2 kit seems pretty reasonable. The biggest hold-up
will probably be if the pipe doesn't fit. I wish more sites went to the
trouble of explaining what the parts are and how much performance you can
expect. We've been very happy with our kitted scooter - it was money well
spent and makes a big difference in performance and safety.
-Dave
"Timothy Jones" <jon...@cfl.rr.com> wrote in message
news:cr8mc.3397$2f6.1...@twister.tampabay.rr.com...
Dennis Lee Bieber
declaimed the following in alt.scooter:
> First be sure to eliminate restrictions in the fuel supply as a possibility.
> If the problem persists, it sounds like a fuel mixture problem. The starting
> problem you have may well be temperature related but not in the way you
> think. Cooler air is denser so on cool days you'll get more air flow for a
> given amount of fuel and vice versa on a warm day. The difference isn't
Strange thought... While one might presume Florida to be
sufficiently warm not to be at risk... What is the humidity? In
particular, what is the dew point...
In short, and I've never known a case in recent decades, but...
could carburetor icing be occurring?
Dave Wood
saying that 2 stroke jetting can be surprisingly touchy and that differences
in temperature, relative humidity and barometric pressure cause enough
difference in air density to be noticeable in highly tuned 2 strokes. Road
racers running two strokes often use air density meters or density
correction charts to help with jetting and are constantly fiddling with the
mixture to get it right. A street tuned 2 stroke shouldn't be that touchy
but there may be some other reason that puts his scooter in a borderline
mixture condition - like an engine with worn main seals etc. If his scooter
is newer and stock, I'd suspect a tuning issue rather than a need to rejet.
His main symptoms - cutting out at high speeds - sounds like classic fuel
restriction but can be ignition issues or excessively lean or rich mixtures.
In any case they should be investigated and repaired. Some of the problems
that cause symptoms like this can lead to seized and destroyed engines if
not sorted out. I have a cyliner/piston from an old RD400 that I road raced
for 3 laps before it seized so bad that the piston melted to the barrel and
the wrist pin pulled out of the melted piston. That engine had soft seized
twice on the same lap but I was too young and stupid to to baby it back to
the pits and kept going - lucky for me the conrod broke and the bike didn't
seize up solid and toss me off. A hard ridden 50cc scooter probably stresses
it's engine similarly to a road race bike - wide open throttle at all times.
A twist'n'go scooter should lock up the wheel, even on a solid seize-up but
it's still a pain and expense to have to fix a blown engine and is
potentially unsafe if the engine goes south at an inopportune time.
-Dave
"Dennis Lee Bieber" <wlf...@ix.netcom.com> wrote in message
news:m8qj9056q0noek68h...@4ax.com...
Dennis Lee Bieber
declaimed the following in alt.scooter:
> I wasn't really hinting at carb icing - especially in Florida. I'm just
Didn't mean to imply that you were -- only that your comments
made /me/ consider that rare effect...
