View Full Version : carburator help help help....

12-01-2002, 11:33 PM
I recently checked out a site,,,and they say that on the standard scooter the intake manifold is restricted,,,
and they say by puting a new intake manifold and a 17.5 or 19 or 21mm carb will improve accelaration and top speed much more,,,,,,is that true?????
They say that if i fit a 17.5 carburator than it will go much better,,,Question??Do i need a new air filter for a 17.5 mm carb that is fitted on a standard cylinder kit with a pipe???or is the malossi red air spunch enough or does it needs a air filter cuz they say i need a air filter just by 19 or 21 mm carb,,,will my engine rev much higher from a new carb ,,,will my my original 50cc cylinder GET DAMAGED FROM a NEW MANIFOLD AND CARB:)

12-01-2002, 11:36 PM
THanks for all advanced people such as:::

THANKS please answer as soon posible,,,thanks:)

12-02-2002, 05:35 AM
Hi there

A larger carb will help you produce more power, but I doubt the difference with carb alone is going to be massive.

you should consider getting a tuned pipe at the same time as the carb, you should also be prepared for the fact that the carb will need to rejetted and roller weights for the variator changed in order to maximise your changes.

Your scooter will not be harmed provided you jet the carb correctly, If you intend to keep your standard 50cc barrell i dont think there is any need to go any larger than 17.5mm carb, but if you are thinking of fitting a 70cc kit later on you will probably better of with a 19 mm one.

I would sugest you decide from the beguining what you intend to do in order not to waste money buying parts that may be unsuitable later on. If unclear speak to a scooter tuner


joe Rubido

12-02-2002, 05:50 AM
Yes i alredy have a tuned pipe a TECNIGAS NEXT and i haave the malossi clutch springs and the yellow big torq spring and im getting new weights,,,,as you said how does the variator weights will change do i need them to be lighter or hevier then before...oh anf why do i need to rejet a new carburator if it comes with the right jet...17.5 carbs come with a jet is that not good??? and why do i have to rejet,,,even by a tecnigas next exhaust??and carbon reeds

tiba karotsu
12-02-2002, 10:21 AM

a 21, 19 & 17.5mm carb will fit your stock manifold with no problems, these carbs don't require rejetting if you still use the stock air box.

well rejetting depends upon many factors but you must test your scooter first using the original jets that came with the carb and go from there, use new spark plugs to get an accurate reading. remember if the color of the plug tip is black you must change to smaller jets and if it's white or light gray you must change to a bigger jet. this should be done after a full throttle run.

if you feel any flat spot when you open the throttle try adjusting the jet needle in the carb slide to give a richer mixture by moving the needle clip postion down a notch, if it blubbers try moving the needle up a notch (leaner mixture).

12-02-2002, 09:46 PM
alright you say it will fit the standard manifold i belive you but people say that is restricted and i have to change it cuz its smaller then the performance one...

12-03-2002, 02:53 AM
aftermarket manifold not required for your set up --just measure the inside diametere --it should be at least 19 mm so 17.5 or 19 carb works fine ..

Doppler manifold is 21mm ID -- hence 21 carb
TP manifold i believe is 25 ID --for 24 or 25 carb --

12-03-2002, 07:04 AM
Is my standard manifold not restricted insede the hole where the gas goes cuz somebody sad that it is restricted in the hole???:)

tiba karotsu
12-03-2002, 08:43 AM

why don't you take off the manifold to see if it's really restricted like they say it is, we won't know until we find out for sure.

12-03-2002, 09:01 AM
u have to check yourself coz each bike varies. when i got my 17.5mm carb i asked mathias did i need to get a new manifold for my benelli. he said he wasnt sure as benelli didnt make their minds up when doing this part of the bike. some they fitted with restricted manifolds-others they had de rezzed ones fitted. anyway i bought a manifold to be sure and as mathias said mine was one of the bikes with a derezzed manifold-i mean the are only like 10 max so its not a major expense!!!

go 4 it


12-03-2002, 11:20 AM
OK thank people about the caRBURATOR inforamtoin and i will check my manifold if its restricted or not....
so can sombody tell what does a bigger carb do such as a 17.5 mm cArb ,,,does it give more power or will it also give some more top end,,,,and some cooling for the crankcase inside and the cylinder ,,,or will damage my scooter or no????? please answer what you people noticed from a carb change///??
Thanks again:)

12-03-2002, 11:23 AM
OH and by the way how do i take of the manifold???

12-03-2002, 01:44 PM
simple. basically remove your carb and right there in front of u is ur manifold. its held on my 3 allen key bolts, remove these and then just take off the manifold.
heres the answer to your question about fitting a new carb, courtesy of WWW.SCOOTER-ATTACK.COM

''Larger carbs supply larger quantities of fuel-air mixture. As the incoming mixture is considerably cooler than the combustion chamber this means better internal cooling of the entire system. And it also means more power. With a larger carb you increase both, power and reliability. Our carbs are supplied with the correct jetting, though sometimes playing around with the mainjet may be necessary. In most cases the original airfilter may still be used.''

and here for the NEW MANIFOLD

''If you decide to use a big-bore carb, you will have to replace the restricted manifold with an unrestricted one. Otherwise the large carb will be useless since it's venturi size is actually reduced to the diameter size of the restricted manifold. Our manifolds will fit any Dell'orto carb up to 21 mm. The deristricted manifold gives better acceleration and better top speed.''

and by the way the manifold u need is only 14.70 euros which is only like 8!!!

hope this helps

tiba karotsu
12-03-2002, 08:02 PM

it's 4 allen key bolts not 3 as ace said earlier, go for a 19mm or 21mm carb, 17.5mm carbs are too small even for mild road set ups (sorry ace no offense intended), i use a 21mm Dellorto on my mildly tuned 50cc Jog scooter, be sure to use the stock airbox so that you won't need to rejet the carb.

12-03-2002, 10:53 PM
Thanks tiba i was thinking also about the 19mm because the 17.5 looks so small to me its like just 5.5mm bigger 19 mm its way better its 7mm more,,,right>>>????
you say i should leave the stock airbox well ok but than the new carburator will give more gas and than my engine wont get enough air???or will it still get air enough and not over heaat???people say that if i put a new carb and set it up right than perfromance is better and coolling also,,,is that true???
Oh and what do you say that your JOG is mildli tuned what is mildli tuned by you???
cuz i just have a exhaust and transmission setup...
oh do i need Carbon reeds for the new carb??


tiba karotsu
12-04-2002, 07:13 AM

yes replace the stock reeds with CF reeds get a set from the forum mall if there's any available.

well in our book mildly tuned means; 21mm carbs, racing CDI, CF reeds, stock 50cc cilinder ported & polished to Malossi sport cilinder specs, Multivar, Kevlar belt, Torque drive half pulley, stock clutch, Malossi clutch springs, Malossi yellow big spring, stock crankshaft, 4N tuned pipes MHR design & 20% gear up kit.

well what do you think? it is mild yes?:D

12-04-2002, 07:56 AM
oh men thats way more tune than on my this is what i have..
Tecnigas pipe
malossi clutch spring
malossi big yellow spring
not yet variator
and of course the cf reeds what i will get
and a 19mm carb

i like to ask because my scooter is not that tuned, what you think will a 17.5 carb perform good with the pipe or will it just give a minimum of perfomance????

Gives the 19mm more or not?? in performance

12-04-2002, 07:59 AM
oh and one more thing you have that 20% upgearkit if you install a new gear will you loose acceleration or not,,will you optain a lot of topspeed>???

12-04-2002, 08:10 AM
an upgrade of your gears-this will make you loose accel on stock setup but if u have like a multivar, clutch etc then you wont be losing accel. a 20% gear raise would give u quite alot of extra top speed iof u had the cylinder to pull that sort of gearing!! i dont think my polini sport or malossi would be able to take full advantage of 20% increase. on a road setup like u are going to do the i think 14% is good enough(maybe tiba can confirm this)
hope this helps

edited by ace2002k

12-04-2002, 12:17 PM
so you say a 14 % will give good performance by me i hope so

tiba karotsu
12-04-2002, 08:36 PM

20% gear up kit works for us 'coz our scooters are much more lighter than yours' or ace's, your scooters weigh around 85kg while ours go for about 50kg and it fully stripped down with no lights. you can pull a 20% gear if you really tune your scooter that is playing (porting) with your cilinders' exhaust & transfer ports, adjusting ignition timing (advancing the ignition timing on 70cc cilinders will give noticeable improvements on acceleration if done correctly),bigger carbs (19mm is OK), oversize reedvalves and a complete transmission kit.

for starters i think the 14% is best with what you have right now and get the 19mm or 21mm carb your 70cc cilinder needs all the fuel & air it can get.


i think your set up can handle a 20% gear up kit provided that you get the transmission set-up good, advancing your ignition timing will help you improve acceleration. stock ignition timing is set for 50cc cilinders so a bigger 70cc cilinder will need a few degrees of ignition advance to make full use of it's power. get an MHR race cilinder (31 8440) and Malossi RHQ pin 12 crank (31 8009) the next time you're out to buy parts.

12-04-2002, 10:18 PM
ok thanks so the 14% is the standard gear..
you say get the 19 or 21 mm CARB and a 70cc kit but here is the thing i dont want a 70cc kit...
and you say as many air and fuel possible???how do i do that?

12-04-2002, 10:20 PM
You say i have a 70cc kit no i just have a standard 50cc kit and not the 70cc kit....i have a pipe but no cylinder...

tiba karotsu
12-05-2002, 02:02 AM

hmmm i thought you already have a 70cc cilinder kit oh well then by all means go get the 19mm carb & 14% gear up kit and be sure to have lots of rollers (& some jets would also help) to tune your transmission (& carbs). don't forget to order a set of CF reeds and use the thinnest reed (.30mm) in the set.

12-05-2002, 06:51 AM
if i put the carbon reeds,usualy how long they last do they break pretty soon or do they last quite long???
SO you say i can put a 14% gear kit up ???
Will i loose acceleration by the 14% gear???or will the top speed go up???i hope i dont loose acceleration by this setup ,,this is what i will have...

Tecnigas next pipe
CF Reeds
19mm carb or 17.5 i dont know yet
malossi clutch springs
malossi big yellow spring
Klevlar belt
Evrything else is Stock

tiba karotsu
12-05-2002, 07:37 AM

you'll lose just a bit of acceleration but the gains in top speed should outweigh the disadvantage brought by the change to a taller gearplus it'll be more satisfying to cruise on the highways without the engine screaming all the time.

12-05-2002, 07:44 AM
so u reckon i should get a new gear set? as on monday if i know the prob with my scoot i will be fixing that and at the same time treating myself to some more tuning parts!! ive got about 400 to blow on my bike!!!(might not go for 400, but 200 is a possibility!!!

if i get the delta clutch and variator and then fit a 14% gear kit how much top speed will i gain? i dont think accel will be that bad as the clutch and variator will cure the loss of accel from the new gears!!
that would be nice to get to top speed and not go deaf from the noise of the screaming bike-it might please my mum aswell-she says always to me ''why cant u have a nice quiet bike like your mates''!!!!!!. i guess she'll never know!!!


tiba karotsu
12-05-2002, 08:34 AM

wow! 400 pounds sterling! that'll get me my MHR Speed cilinder & Team crank, say could i borrow it for a while?:D just kidding:lol:

well it depends but from the variator & gear change i'd say you'll hit 70mph if you get the set up right, a bit more tuning and you'll nudge a few MPH more. don't forget to include the Malossi Clutch bell it's a must have for the Delta clutch, why don't you get the MHR OR kit along with the Delta clutch, Clutch bell and gear kit. you'll be half way thru just by getting the whole transmission system and after that an MHR cilinder & crank to complete your transition from mild to wild, 400 UK pounds is a lot of money and i have that much to blow on your scooter i'd get the parts i mentioned along with the racing CDI & coil.

now if your mum was into scooters you would have to make turns riding it with her and i don't think you'd want that do you?:lol: so are you one of us? (scooter tuning freaks that is) if yes then let the tweaking begin!:evil:

12-05-2002, 09:36 AM
Whats with all the talk of putting 19 and 21mm carbs on 50cc and 70cc sport kits? Kind of overkill I'd say, you would be hard pressed needing anything bigger than a 17.5 on a good road setup.
If you want the extra power, just use a more free flowing filter pod and jet up the 17.5, anything over a 17.5 in particular on such a small engine is a waste unless you have got a very good (read loud) pipe and have lots of other mods and are lookin for that last 10/10th of power.

The bigger carbs just make the bikes harder to ride and more sensitive to throttle, the smaller carbs make the engine smoother and more forgiving, without missing out on any real power.

This guy sounds like he wants something smooth and easy to ride with just a bit more power, I don't see the point in trying to convince him he needs to go big and spend more than he needs to.

12-05-2002, 09:57 AM
uve mistaken me!!! within the next few months im gonna transform this current piece of @#%$ i have into a real racing machine as tiba says. current i have a polini 4race pipe which is extremely loud!!! when i was riding it on saturday and sunday the looks i was getting were unbelievable- god knows what u must get dutch with your EVO pipe.

there was one senario: went passed a speed cam at a nice 30mph and then onto a lovely straight. id noticed the lights had just changed to green so i just went flat out down this mile and a half straight and i went passed a packed bus stop-they all turned their heads.

its funny what a little bit of noise can do and how it can intimidate other 50cc riders!!! before when stock i always had shitty little italjet badboys coming up next to me a revving signaling for a race, this never happens anymore, which is a shame-id love to smoke one of them things!!! the only raced ive had since putting my bike to 70cc was a motorroma wasp fitted with a leo vinci sprinter pipe-his bike was OK on accel but i still beat it and he was gone when i looked back!!! he must of turned off coz he looked like a knob!!!

anyway cheers for the advise bishop but im ambitious when it comes to the tuning. between now and april i will have roughly 120 each month to spend on the scooter so im gonna make the most of it!!

dutch u dont fancy having an aprilia rs125? 1500?? or u tiba?


12-05-2002, 10:12 AM
Just don't go trying to stick a stock air box onto a 19+mm carb, that should be a crime, it kind of defeats the whole idea of getting a larger carb in the first place.

Loud is good, stops the cage drivers from using the whole "I did not see him line" when they almost hit you, cause they damn well should have heard ya!

12-05-2002, 10:15 AM
Heh, I did mix you up with Laz didn't I, silly me, teach me to post at 1:30am in the morning...


tiba karotsu
12-05-2002, 10:37 AM

i had a nice laugh when i read your post i wish i were there to see those Italjet boys and the Motorrama wasp square off against you in a drag race. BTW ace how old are you? how much do weigh? just curious if you're rider material.

Bishop there are no laws about speeding where i live so most tuning parts sold here are the full race MHR/EVO kits, none of the Sport or Corsa used for the streets and if every person with loads of money can have his way he'll slap on a full MHR/EVO race kit just to use for the street.

and ace inform me as soon as you get the whole transmission kit and clutch 'coz i'll send you some MHR clutch spring for your Delta clutch when you buy my EVO race pipe.

12-05-2002, 11:07 AM
17 yrs old-im def not rider material like the peeps you employ to ride ur drag racer!!! im quite tall though so thats against me aswell

i think the EVO pipe will have to wait until january but i will confirm this when i check my account on tuesday
im still not decided weather to get the OR kit again i will decide on tuesday!!

im def getting the CDI(dunno if i should chance the malossi cdi?), clutch, coil possibly the ignition and if not the OR kit i will def get the multivar and gear kit!!


tiba karotsu
12-05-2002, 11:52 AM

you're the same age as my rider Micol and i didn't employ him to be my rider i chose him and he accepted with one condition; i tune and work on his scooter for free as long as he races my Jog.:D

well any racing CDI is better than a busted one so go for anything that'll fit your budget as long as it's a good brand. here's my final suggestion for your shopping list on Tuesday;

CDI, OR kit, Delta clutch, clutch bell ,gear up kit!!!
CDI, OR kit, Delta clutch, clutch bell, gear up kit!!!
CDI, OR kit, Delta clutch, clutch bell, gear up kit!!!

the EVO race pipe can wait as i'm earning money as quickly as i can, i already have a buyer waiting to get my MHR crankshaft for the Honda Dio SR (see i also have an SR but it's not an Aprilia:lol: ) maximize the use of your For Race pipe and gain more knowledge & experience by doing your own work, learn from your past mistakes so you wouldn't repeat it again only by becoming wiser will you hope to get faster.

12-05-2002, 01:10 PM
alright people thanks i will put a new filter and a 17.5 or 19 carb depends on the price....
I hope it will go right and fly from acceleration...
Oh and of course what do you people think howmuch my bike would go with the new gear kit 14%

remember without 70cc will my standard 50cc pull the 14% gear good with mods i have???

tiba karotsu
12-05-2002, 08:14 PM

do you know the stock gear ratio of your scooter? to measure final gear ratio count the number of times the clutch bell must turn (360 deg = 1 turn/revolution) in order for the rear wheel to make 1 revolution, just put a marker on the clutch bell & the rear wheel and start turning the clutch bell.

you should do this too ace if you want to know how much gearing we'll really need to make your scoot faster.

12-05-2002, 08:28 PM
oh thanks i think i will do that latter now im focused on my
CF reeds and carburator and my transmission springs what will arive tomorw...
Oh is that really true what that guy says ( BISHOP)
that a 19-21mm carb is a overkill for the bike neaby for the 50cc but not for the 70cc thats what i think..
ok what else should i do to not damage my scooter ,,,some other tuning tips after the carb???but no 70cc kit,,,
oh do you know how nuch my yamaha aerox is doing in RPM right now with the Tecnigas next PIPE ??????
How in the hell can i test my rpm cheaply with out anything to buy?? do Dealers have rpm and horspower testing machines??? or how:)

12-06-2002, 03:42 AM

i have question ? why you insist on aftermarket CDI ---how about just discoenect the blue wire on stock CDI ?

also Kitaco nolonger sell anything for 2 strokes (at least not in thier website) so no more Kitaco CDI --

also why dont you go to thicker reed than .3 ? they last longer and maybe more peak power ..

my scoot got stolen --i can get another one but its been cold and raining day and night so i lost interest -- i still have few performance part left ;;;so maybe i built another scoot --so far i lost 2 scoot --lotsa time and efforts lost


19 carb get you no more power on stock 50cc cylinder BUT if you decide to go to 70cc etc you need 19mm or bigger -

tiba karotsu
12-06-2002, 07:59 AM

well we do make our own racing CDI here as copied the most popular CDI on the market and we improved on that by installing a bigger capacitor.

we still have plenty of Kitaco CDI here but who'll spend P3,000 on a CDI when they can have a better custom CDI for half the price:D

i use .30mm CF reeds 'coz they're single petal (on each side) and they're stiffer than a .30mm CF reeds with 2 petals, i have made a set of .35mm reeds to test on my Jog but the opportunity hasn't presented it self 'coz the cilinder is on it's last legs (nicasil peeling off:( )

12-06-2002, 09:18 AM
ok do any body know how to test my bike how much RPM IT DOES?????

12-06-2002, 09:20 AM
Oh and does a Air filter on a standard carb with rejeting

Will i get more power or nothing from a airfilter??? on a stock carb rejeted???

12-06-2002, 09:57 AM
when u fit a power filter on a stock carb, cilnder etc you dont really get more power-slightly better acceleration-the main benefit of a power filter is the noise they give ur bike. they do make ur bike sound very nice, especially on accel!!! they are a good mod to get started and only cost about 20 for a polini filter

12-15-2002, 05:07 AM
Im new to this forum and Ive just bought a SR50 1998 Rossi Replica and I was reading these messages about carbs and CDIs and want to know whats the advantages and any disadvantages of disconnecting the blue wire from the CDI unit? 8o

tiba karotsu
12-15-2002, 10:20 AM
nothing at all if speed is what you're after but you have to factor in increased fuel consumption and faster wear & tear on your motor if you keep revving it at redline all the time.

the one with a disadvantage here is the tuning parts dealer 'coz you won't need a derestricted (racing)CDI from them so there's no sale, no profit.:lol: