2002 50cc BWS Air box

[davybondo]

Hi

could someone please tell me the size of the air intake hole of the stock air box

where the air comes in not into the carb

 there is a small snorkel in there mine was taken out by a stupid mechanic

I've gone through 2 cylinder kits sized solid before I noticed

I have a jet kit but cant get a jet big enough

now I'm running a 92 Main and 46 pilot

I cut up a piece of 1/8" rubber gasket to down size the hole and it's a lot better but I'd sooner have the right size

mine measures 23mm

it has the stock carb and after market pipe

I'm running mixed gas at 40-1, 32-1 was way to smoky

I have to get this sorted before I put in my 3rd 70cc kit

Thx for any help you can give me

[Zino]

i have built a few zumas
i only have airbox with snorkle out
i have run both snorkle in and snorkle out the jetting difference was minimal just one jet size.
snorkle in 85 snorkle out 87.5

I ran genuine mikuni jets with the oil pump
since you are premixing 40 to 1 which is plenty oil you run a jet 2-3 % bigger.
Mikuni jets 85 -90 was the outer edges of what  worked well for me .
So a 92 if its a genuine mikuni sounds close to what i would run .
I also ran the 46 vino pilot jet to richen the stock carbs full throttle range .

If you are seizing 2 kits in a row .
You might have an air leak either in the crank seals or around the intake reed cage .
The stock carb is not quite enough for high revving kits and pipes its not rich enough coming off throttle and mid range .
It works ok to good with the sport cast iron kits and builds that revs up to low 9000 rpms.

What kit are you running ?
Did you do a leak down test ?

I would invest in a good temp gauge to monitor day to day health
alot of guys use 350 degrees as a upper limit for long wide open runs .

[davybondo]

I have a new intake, reeds and cage, cheap set though and the stock delorto carb
jet kit I used is Polini
could you recommend a carb, intake, and reed setup for me
I have an Athena 70cc Aluminum cylinder, the other two were Malossi cast iron
and I'm gonna do a leak down test like you said,I should have done that
I'd say your right
I love this scooter I just sold my GSXS 1000 cause the bws is way more for fun
but it's costing a lot more money though ;-)
Thx for your help and reply

[Zino]

plenty of zuma threads to follow
search around the malossiand Athena are solid kits that should give you thousands of miles of fun
I have 3 scoots in my garage right now with Malossi kits

49ccscoot.proboards.com/thread/26853/zinos-zuma-sport-build-sold

I have run both the malossi and athena kits on my zuma with a yasuni r turning over 10k rpms
The stock carb is not quite enough for that level .
It does not provide enough cooling fuel mixture For long wide open runs .
I like the 17.5 dellorto carb and the 19 mm dellorto carb that is as big as you will need for best performance you will have to grab a single pull throttle cable for it .

On the Left side of this page search the directory for a leakdown tester and how to make and use or follow tune goons
49ccscoot.proboards.com/thread/30732/diy-leak-tester-cheap

[davybondo]

Thx the leak down tester looks great and the thread you posted so much info
I'm gonna order up a 19mm Delorto, intake and reed cage before installing this next kit
and the leak down test
I've got a temp gauge on the way too, Runleader Digital LED
Thank you so much

[Zino]

with you running air box
you will need dellorto 5mm main jets in 80 to 90 range

the dellorto jets you have for the stock carb are 6mm dellorto they are for the 17.5 dellorto.

[davybondo]

got all the stuff ordered I had to go with the Naraku 19mm cause the Delorto's were back ordered
and the Polini needed an adapter for the air box

Single Throttle Cable conversion Bws-Zuma
Carburetor Naraku 19mm PHBG
Main Jet Set Stage6 Dellorto 5mm 70-92
Choke lever Stage6 150cm
Intake manifold
Reed Valve Gasket

I had to send the Antena 70cc cylinder was bent at the bottom, I can't wait to get it all done now
you've been a great help Zino
Thank you

[Zino]

start a build thread so we can help you out along the way and the next guy can learn from you

[davybondo]

I'll try, it took me forever to figure out how to post this question

[davybondo]

Hi

well I'm installing the new Athena 70cc kit

I have the thinnest gasket on the bottom of the cylinder

and when it's bolted together with the aluminum head gasket

the piston just about touchers the 1.5mm solder

so I did a visual check with a spare Mallosi head and tried that with the rubber ring gasket

now I'm getting 1.2mm squish

Athena calls for 0.9mm

do you think the Mallosi head will be ok

what do you guys think I should do

any help would be really appreciated

I did a pressure test before I took the motor apart as well

with a 15lb air gauge set at 3lb pressure for half an hour and it drooped the withe of a needle

which I was really happy with

I found a crack in the rubber intake

[aeroxbud]

What is the squish and port match like without the gasket? You could just use copper spray gasket maker if it's better.

[davybondo]

I never thought of that Thx

I'll try that today

[Zino]

Tighter squish give a more spunky take off from higher compression.
Lower squish leads to higher port timing that gives you more rpms and top end .

As long as you get below 1.5 you will be fine .
Ideally you will get tight squish and have your boost ports bottom edge even with the top of the piston this way you maximize the port timing.

[davybondo]

Thx for your reply Zino

that makes me feel a lot better

[davybondo]

Hi

is there a secret to tuning a Mallosi MULTIVAR Variator

I can't get the belt lower on the pully, it's about an inch to high

it's a 759 by 16 as far as I know that's 19mm longer than stock

are they designed to be installed with the starter gear removed

if I use the 2 mil washer that they say to use then there's no room to use shims

I have a 1mm shim installed first

then the pulley and roller half then 1mm shims then the 2nd half

and there's just enough threads left to get a full thread for the kick start gear and the nut

if I use my old stock belt which is down to 14.5mm wide it works great

I'm just on my 2nd warm up and cool down with the motor

and it sounds strong

the Trail Tec temp sensor is awesome wow

I'm taking it up to 210f each time