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DRZ 400 Airbox Cover Mod?

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So I’ve got a 2007 Drz400S that I’ve done a 4x3 airbox mod, Stage 2 Hotcams, 434cc Cylinder works big bore kit, powercore4 + megabomb header and a Lectron 38mm carb. But I’m looking to get a little more airflow out of it. Has anyone cut a small hole in their airbox cover before kind of like how Dirtbikes have a more open airbox?

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You do not need more air. In fact, you have more than enough now. Adding more air causes you to make the carb settings richer. But you are not really adding more fuel, you are just compensating for less vacuum signal (vacuum that dulls fuel up in to the carb throat). Easy 'proof of concept. Ride your bike over a long course. A repeatable ride where fuel usage is the same. Then remove the airbox door, adjust the carb to compensate and ride the same course a few times. Compare mileage. It will be the same.

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3 hours ago, Keegan Lynch said:

So I’ve got a 2007 Drz400S that I’ve done a 4x3 airbox mod, Stage 2 Hotcams, 434cc Cylinder works big bore kit, powercore4 + megabomb header and a Lectron 38mm carb. But I’m looking to get a little more airflow out of it. Has anyone cut a small hole in their airbox cover before kind of like how Dirtbikes have a more open airbox?

Like this ?

How much do you think that piddly 38mm carb will flow ??? 🤣🤣

20200119_152515.jpg

20200606_170747.jpg

20200310_154531.jpg

Edited by Tony Wyp

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3 hours ago, Tony Wyp said:

Like this ?

How much do you think that piddly 38mm carb will flow ??? 🤣🤣

20200119_152515.jpg

20200606_170747.jpg

20200310_154531.jpg

Lectron did quite well actually cut a triangle on the flared part of the airbox cover to catch air, that little bit did a good number and don’t underestimate that 38mm Lectron. Those carbs rock

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6 hours ago, William1 said:

You do not need more air. In fact, you have more than enough now. Adding more air causes you to make the carb settings richer. But you are not really adding more fuel, you are just compensating for less vacuum signal (vacuum that dulls fuel up in to the carb throat). Easy 'proof of concept. Ride your bike over a long course. A repeatable ride where fuel usage is the same. Then remove the airbox door, adjust the carb to compensate and ride the same course a few times. Compare mileage. It will be the same.

My carbs adjust for that difference with a metering rod. It did make a pretty noticeable difference actually 

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51 minutes ago, Keegan Lynch said:

Lectron did quite well actually cut a triangle on the flared part of the airbox cover to catch air, that little bit did a good number and don’t underestimate that 38mm Lectron. Those carbs rock

A 38mm hole is still a 38mm hole no matter how much snake oil you swallow and money you spend.

Lectrons arent magic 🤥.....or, are they ?

I dunno cos i aint tried one. They want $1,500.

Im used to paying $150 for FCRs. If I ever see a cheap Lectron I will get it to try and see what the hype is all about 🙂 but they are scarce if non existent here.

The MAIN thing is, YOUR bike runs great and YOU are happy.

What more can a bloke ask for !

 

Edited by Tony Wyp

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1 hour ago, Tony Wyp said:

A 38mm hole is still a 38mm hole no matter how much snake oil you swallow and money you spend.

Lectrons arent magic 🤥.....or, are they ?

I dunno cos i aint tried one. They want $1,500.

Im used to paying $150 for FCRs. If I ever see a cheap Lectron I will get it to try and see what the hype is all about 🙂 but they are scarce if non existent here.

The MAIN thing is, YOUR bike runs great and YOU are happy.

What more can a bloke ask for !

 

For sure scarce, $1,500 is bizarre I paid $650 which is still steep but it’s still pretty new on the market and FCR’s are roughly $350-400 around here used

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2 minutes ago, Keegan Lynch said:

For sure scarce, $1,500 is bizarre I paid $650 which is still steep but it’s still pretty new on the market and FCR’s are roughly $350-400 around here used

My prices are in NZD.

ex 450 motocross FCRs are only USD100-ish, here. A Bargain.

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14 hours ago, Tony Wyp said:

My prices are in NZD.

ex 450 motocross FCRs are only USD100-ish, here. A Bargain.

Oh for sure I would’ve definitely gone FCR if it was that cheap around here and just sucked it up with the jets. I’ll get mine dynoed soon and see what the numbers match up to. The only real advantage I see out of the fcr’s is that accelerator pump but that mostly helps with mid to top end and I ride a lot of a Somewhat slower pace trails at various elevation. I’m hoping it pulls atleast 43-44hp

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4 minutes ago, Keegan Lynch said:

Oh for sure I would’ve definitely gone FCR if it was that cheap around here and just sucked it up with the jets. I’ll get mine dynoed soon and see what the numbers match up to. The only real advantage I see out of the fcr’s is that accelerator pump but that mostly helps with mid to top end and I ride a lot of a Somewhat slower pace trails at various elevation. I’m hoping it pulls atleast 43-44hp

Whatever you get is somewhat meaningless.  Dynamometers are useful for measuring before and after gains and nothing else.  What your maximum horsepower is vs Joe Blow's on another machine isn't comparable.  A while back, we had some knuckle head try to say the 3x3 was bad because his jetted but otherwise stock bike pulled nearly 40 HP at whatever shop.

I've had 5 different carburetors.  A 39mm FCR will gain horsepower everywhere on even a stock displacement engine   The magic of the FCR and the reason why 4 strokes made a comeback as race bikes, was it's ability to tune out the dreaded cough and stall. Your thinking of the accelerator pump is backwards.  By having a pump, you can run a larger bore carburetor for maximum power yet still have strong low end response from the injection of fuel directly into the intake.  By running an undersized carb , you get good low end response and nothing else. This is why play bikes with non pumpers have such small carburetors in comparison to race bikes. This is also why they have a little burst of power right off idle and little else.

 

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