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Author Topic: Removed air box restriction  (Read 1999 times)

old geezer

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Removed air box restriction
« on: June 02, 2012, 10:55:48 PM »
I removed a restriction in my S 250 air box cover. I don't know if it runs faster but it is a little louder.

The air box with the tube that restricts air flow.



Restriction in the air inlet



Tube removed, air inlet in side dia much larger.



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zombie

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Re: Removed air box restriction
« Reply #1 on: June 03, 2012, 03:20:21 AM »
More air= More fuel. Keep an open eye.
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old geezer

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Re: Removed air box restriction
« Reply #2 on: June 03, 2012, 01:49:37 PM »
The main jet is .104. I have jets in sizes of .105, .108 and .110. That should fix things if needed.
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gregspeople250

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Re: Removed air box restriction
« Reply #3 on: June 03, 2012, 08:32:27 PM »
Is the ID of the carb any larger than the "restrictor" ID?
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zombie

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Re: Removed air box restriction
« Reply #4 on: June 03, 2012, 08:40:12 PM »
1980's Johnson outboards used the same technique to change their HP ratings. The 9.9hp twin could be the 15hp by drilling out the intake. Same for the 20hp twin. It became the 35hp just by removing the restriction. Of course up jetting was always needed.
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old geezer

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Re: Removed air box restriction
« Reply #5 on: June 04, 2012, 12:23:24 AM »
Quote from: gregspeople250 on June 03, 2012, 08:32:27 PM
Is the ID of the carb any larger than the "restrictor" ID?

The ID of the carb is much larger than the restriction.
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gregspeople250

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Re: Removed air box restriction
« Reply #6 on: June 06, 2012, 10:21:55 PM »
Cool!
Can you measure the performance to determine if there's been an improvement?  Probably need larger jets to take advantage of any additional intake air.
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Honda Elite 80 - SOLD
Yamaha Vino 125 - SOLD
Kymco People 250 - SOLD
Kymco Like 200i - SOLD
Vespa 250 GTS - SOLD
Piaggio BV350 - FUN! - SOLD
Buddy 170i - FUN! - SOLD
Honda Silverwing - SOLD
Yamaha TMAX - OUTSTANDING! - SOLD
Honda SH150 - SOLD
Yamaha SMAX - SOLD
Kymco AK550

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