Kawasaki KLR 650 Forum - Reply to Topic
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

Thread: L mod Airbox mod Reply to Thread
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  Topic Review (Newest First)
04-03-2013 08:11 PM
Tom Schmitz I never noticed noise from the L-mod. Yesterday I did a test with the door off yesterday. That was loud! As loud as another muffler at times. In testing yesterday I found that pulling the snorkel leaned the mixture out by about 1 point. T
04-03-2013 08:00 PM
salty_monk In a recent Dyno run on .net they did get a HP increase by removing the door (KLX needle & 140 or 142 jet plus Uni filter).

I believe you must use the KLX needle though from any research that I have done on this. Stock needle & jet works best with stock airbox...
04-03-2013 04:43 PM
willys IMHO...if you get the 4 or 5 holes in the top of the box, you have enough air flow getting to the aircleaner that the engine can suck into it. The 39mm opening of the carb intake can only get so much air through it and in the pic above there is far more open spaces created than the size of the carb intake size.....I'm thinking.
Plus way back when it was proven that removing the door wasn't the best way possible to get air into the airbox compared to these 4 or 5 holes were. Seemed that the airflow was better this way. You will need to search the threads on other sites to get this data though. The world I think is where it is.

This is also another topic that has been beaten to death over the years and always creates interest. Being from the era of 7 years ago when there was much interest for the almighty HP many small things were being tested and proven with flow tests and dyno runs. Now a days the dyno runs and flow tests are few and far between as costs go through the roof for the time on the machines. If a mod makes enough of a difference that you can feel it then on a KLR that is pretty good. It's not like the bike is so fast we are fighting for HP numbers that are dangerous to feel.

But hey stay with it, it's all good and fun to watch and learn.....
04-03-2013 04:16 PM
salty_monk Wondering why the holes are not drilled in the box on the right hand side of the frame tube to mimic what is done on the left hand side as stock..
Anyone tried that? I don't think you could get as big as an opening equivalent to this though, just wondering if the noise/airflow might be better from there.

Is it just a space thing? Easy access?
Perhaps having it under the seat is better than having it under the side cover on the right? There is certainly less space to drill in that back corner...

04-03-2013 03:48 PM
Originally Posted by Tom Schmitz View Post
Dwell -

What SLO-KLR said. +1.

I'm a believer in not doing irreversible mods, so I recommend poking 1" holes that you can pop plastic plugs into if you don't like the results, or if you put a really loud muffler on and find that later on you want the stocker back on and have to rebalance the airflow. Ask me how I know about that...

Notice how that forward hole is only half a hole? Be careful where you cut - I miscalculated and got half the hole on the carb side of the baffle and had to patch it. Oooops. Fortunately it is made of ABS, so making a patch and cementing it in was easy. The plugs for the holes are available in those bins/drawers of miscellaneous hardware at Home Depot, Lowes, ACE, etc..

Are you also going to pull the snorkel out? It's usually done with the L-Mod.

A few strips of duct tape take care of plugging the holes as well, I just didn't care for the intake noise.
03-30-2013 06:48 PM
Tom Schmitz Open area of the back fire screen.

I measured the opening (a radiused rectangle) at 2.45" X 3.80".

That's a total area of 8 in^2 (rounding).

I could not directly measure the screen material without destroying the air box, so I did it with a picture. I figured out what the area of an opening in the screen was compared to the area of the wires making up two sides plus the open area of the rectangle in the screening material.

My best estimate is that the screen material is 56% transparent (rounded).

That gives an open area of the screen of 4.5 in^2.

The snorkel hole (with snorkel removed) is 3.12 X 1.57 with ~9/16 radius corners. That gives and area of 4.8 in^2

With the snorkel removed and a normal L-mod done the airbox has a total area open of 3.14 in^2 + 4.8 in^2 = 7.93 in^2.

I noted (and it probably only truly applies to the set-up I had at the time) that when I went from 3 1/2 holes to 4 1/2 holes the AFR did not lean out any further.

Thus, 8 in^2 (air box openings) going into 4.5 in^2 (backfire screen opening) into 2 in^2 (throttle bore) seems about the right thing to do.

By now Messrs Bernoulli and Venturi are probably spinning in their graves...

03-30-2013 12:20 PM
650Stew Ya nailed it Jeff!
03-30-2013 12:14 PM
Originally Posted by Tom Schmitz View Post

Thanks Tom, that took some searching! I'm not a cigar man but I will virtually drink your beer!
03-30-2013 12:08 PM
Tom Schmitz
Originally Posted by justjeff View Post
From the 1968 Beatles cartoon movie Yellow Submarine referring to breaking the glass. You cant, its "Beatle proof", nothing is "Beatle proof".

03-30-2013 11:01 AM
Originally Posted by Tom Schmitz View Post
Truth be told, I drilled the half a hole first. After a short session of self flagellation, I returned to the scene and fixed it.

Then I drilled the second hole and checked the AFR, drilled the third and checked the AFR, then the fourth and fifth. The AFR did not change with the fifth hole.

I'm glad I have the half a hole, though, because nothing is Beatle-proof.
a virtual beer and cigar to the first to explain the reference.

From the 1968 Beatles cartoon movie Yellow Submarine referring to breaking the glass. You cant, its "Beatle proof", nothing is "Beatle proof".
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