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Airbox Mod (with success)

647 Views 3 Replies 4 Participants Last post by  pego30

So recently i have been testing my RS with open pods, airbox with, without, and modded snorkel.

My setup is Italkit 140cc ported with widened exhaust port, and enlarged intake port. Approximately my port map is, exhaust open at 79deg after TDC, 209 exhaust duration, transfer opens at 117deg and closes at 248deg. 0.7mm squish with about 12cc chamber.
32mm "custom" PWK carb.
Zeeltronic CDI with timing at 10.5k/rpm-18deg and 12k/rpm-8deg.
0115 Jolly belly with 40mm length manifold.

My past issue is at RPM at 11~11.5k, the powerband would sometime abruptly end as if the main jet felt too big or too small.
As I have stated above, I tested with open pods or with airbox and with or without snorkel mods. it would almost have the same result.

So I gambled and commissioned to 3D print a huge snorkel. Inside cross section is about 40x80mm. (am planning to make it a bit smaller to 30x75). it barely fits, but need i to cut away a part of the radius as it was hitting the tank.
The verdict there is even more power at 10k till 12k and there was an overrev till 12.5k (I guess meter does not go pass 12k). Even my power drop was gone.
Previously my powerband felt very narrow where i need to change at 11.5krpm at 5th gear (155km/h) to continue to 6th gear, to stay in the powerband. (a power drop around 9.5k~10k and a surge after.
with the custom snorkel, I can even full throttle from gear 6 with no issues. (175km/h)

Speed is based on the Aprilia meter with 150/60x17 tire.
I have tested it with PKW 35mm with similar results. (i used 32mm as 1/4 to 3/4 throttle position is cleaner)

if you are aiming powerband for up to 12k rpm, you will need the airbox with slightly bigger snorkel.
if usingAarrow/Gianelli just use the original snorkel. (pipe usually peak at 10~10.5k)

i guess someone from this forum was right, the airbox was designed with a purpose. I believe the snorkel was calculated to max out at around 11k (140cc) or maybe 12k if (125cc)

do comment if you find something odd with my setup.

Automotive tire Motor vehicle Bumper Automotive design Automotive exterior

A part where i cut away so i can close the tank fully
Hood Bumper Motor vehicle Gas Automotive tire

my bet is the tank is currently resting on the snokle when its closed. The snorkel is attached via 3 screws and sealed with double-sided tape and instant gasket maker.
Tire Automotive tire Motor vehicle Wheel Automotive lighting

View from the front.
Carb has a 60mm Intake, instead of standard of 50mm from Keihin or those chinese copy of 56mm ish.
Table Wood Hardwood Rectangle Plastic

Snorkle has 2 parts outside and inside, to mimic what original snorkle was. It fits nicely inside of the airbox too. part is mated like make/female and secured with JB weld.
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Looks nice , I may copy this
Nice work at least your giving it a try and also have some results I think I have a spare lid somewhere hmmm. I have an early TZ 125 for the track and it was just straight out to atmosphere OK on the track, but the later ones used an in take in the front of the fairing to a large air box I guess controlled volume as they revved at 12-13 k .I think it's interesting to have a go and get results ,way to go .
No no no and no

leave the airbox alone and concentrate on ignition timing and a decent pipe

140cc wiill rev out to 13k with a aftermarket cdi and a decent oipe
Like jolly moto corsa or custom fabbed one

the air box design shouldn’t be messed with
1 - 4 of 4 Posts