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Discussion Starter #1
Man...

Did the airbox mod yesterday. Today, 200+ miles later, all I can say is what a difference. The power range has smoothed out so much. I no longer have a lerch at 7000 rpm. It is smooth across the entire power band.

Not only that, but there is a new (pleasant) growl to the engine.

If you haven't done this mod, do it.

Thanks, again, FOG.
 

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kevlarian said:
Man...

Did the airbox mod yesterday. Today, 200+ miles later, all I can say is what a difference. The power range has smoothed out so much. I no longer have a lerch at 7000 rpm. It is smooth across the entire power band.

Not only that, but there is a new (pleasant) growl to the engine.

If you haven't done this mod, do it.

Thanks, again, FOG.
Did you switch to a K&N filter and do the pilot screw tuning?
Just Curious...
 

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Discussion Starter #3
MrSciTrek said:
Did you switch to a K&N filter and do the pilot screw tuning?
Just Curious...
Nope... neither... I was going to do the pilot screw adjustment after getting a K&N, however after my ride today, I doubt I want to mess with anything... maybe I will still do it, but man... what a great ride!
 

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Lucky#13 said:
Just wondering , could you explain the advantages and disadvantages of doing this mod. I have plenty of technical ability to do mods or even rebuilds . The power range on my 02' is a tad slow between 60-80 mph(takes about 5.5-6 sec.) , but does the mod affect the gas milage ? My thinking is that any mod that increases power , and or hp would decrease mpg.Am I correct .... I might just be completely wrong.If so please explain either way.
OK the Airbox Mod: Exs and most carburetted bike are rich on top because the EPA make them lean on the bottom (that's the way the test is skewered). So to lean out the top without changing jets or needles, I reduced the Air Box Vacuum (the 1" hole) This doesn't increase the airflow, it just adjusts the vacuum balance between the intake tract and the fuel bowl. This would usually have the effect of further leaning the low speed running. Hence the pilot screw adjustment. I'm supprised that your Bike doesn't have a real low speed stumble.

Power increases come from burning more fuel. Either by emitting more, or using what's there more efficiently. Since we opened the pilot screws, we fall into the added fuel category,this= lower MPG.

FOG
 

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Discussion Starter #5
FOG said:
OK the Airbox Mod: Exs and most carburetted bike are rich on top because the EPA make them lean on the bottom (that's the way the test is skewered). So to lean out the top without changing jets or needles, I reduced the Air Box Vacuum (the 1" hole) This doesn't increase the airflow, it just adjusts the vacuum balance between the intake tract and the fuel bowl. This would usually have the effect of further leaning the low speed running. Hence the pilot screw adjustment. I'm supprised that your Bike doesn't have a real low speed stumble.

Power increases come from burning more fuel. Either by emitting more, or using what's there more efficiently. Since we opened the pilot screws, we fall into the added fuel category,this= lower MPG.

FOG
FOG,
I have not noticed ANY low speed stumble, however, I tend to run the bike in the 6000-9000 RPM range most of the time, so maybe I just don't run it there enough to notice.

From a complete stop, I have not noticed any issues with the power range OTHER than it has smoothed out the entire range.
Kev
 

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Discussion Starter #6
FOG said:
Lucky#13 said:
Just wondering , could you explain the advantages and disadvantages of doing this mod. I have plenty of technical ability to do mods or even rebuilds . The power range on my 02' is a tad slow between 60-80 mph(takes about 5.5-6 sec.) , but does the mod affect the gas milage ? My thinking is that any mod that increases power , and or hp would decrease mpg.Am I correct .... I might just be completely wrong.If so please explain either way.
OK the Airbox Mod: Exs and most carburetted bike are rich on top because the EPA make them lean on the bottom (that's the way the test is skewered). So to lean out the top without changing jets or needles, I reduced the Air Box Vacuum (the 1" hole) This doesn't increase the airflow, it just adjusts the vacuum balance between the intake tract and the fuel bowl. This would usually have the effect of further leaning the low speed running. Hence the pilot screw adjustment. I'm supprised that your Bike doesn't have a real low speed stumble.

Power increases come from burning more fuel. Either by emitting more, or using what's there more efficiently. Since we opened the pilot screws, we fall into the added fuel category,this= lower MPG.

FOG
FYI - MPG has gone down w/this mod. I was averaging around 57-59 MPG, now i am getting about 53 MPG. That is about a 7% reduction in fuel economy, and I still have not adjusted my pilot screws... they are set to the factory settings. Just a note... my bike always smelt like gas fumes when running idol. I don't know if this is an indication as to why I may be running fine without a pilot screw adjustment.
 

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"... my bike always smelt like gas fumes when running idol. I don't know if this is an indication as to why I may be running fine without a pilot screw adjustment."

It sure is, you have a incorrect float level or a leaking float valve (Stuck float syndrom)
.
FOG
 

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Discussion Starter #8
FOG said:
"... my bike always smelt like gas fumes when running idol. I don't know if this is an indication as to why I may be running fine without a pilot screw adjustment."

It sure is, you have a incorrect float level or a leaking float valve (Stuck float syndrom)
.
FOG
And the fix would be...
 

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Yes , but more importantlly, determine that the float valves are not leaking. It's quite common for debris to get lodged in the valve that prevents it from completly closing. Be sure to back flush the line to the tank and install a inline filter.
FOG
 

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what exactly is the FOG airbox mod? i understand it involves putting a one inch diameter hole in the airbox...where exactly on the airbox?
 
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Is there anything wrong with putting the hole elsewhere in the airbox, like in the cap that secures the air filter.
 

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The Obvious question is : Why? What could be easier than removing the left side cover and drilling it on the bench? I never tested any other location. If you want to try one go for it. Maybe they'll call it the Smithmax air box Mod.


FOG
 
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It's what I did a while ago with my brother since the cap was off anyways. It made a bit of difference w/ sound and probably performance.
 
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