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Discussion Starter #1
Mains are 150/155, pilots 22.5 (25s on their way)
HMF slip on exhaust with stock header pipe
No other intake/exhaust mods

Drilled some holes in the air filter box cap and removed the snorkel and installed a k/n filter on the crankcase breather hose. My idea was to open up the airflow a bit without removing the airbox entirely and spending a decent amount of time and money on it. It runs alright enough, no loss of power or stumbles, but it sounds a bit like it's under water or like your ears are clogged up making everything sound kind of "muddy." It sounded great with everything stock. The sound difference is pretty subtle, it's not like it sounds absolutely terrible or runs like crap. Any input would be appreciated.

According to HMF, they recommend either 150/155 or 155/160 with a modified airbox.
 

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Pull the air box lid off and run it. See how it sounds then. I run Uni vents, have run them in all my air boxes since the 80's. Outerwears also makes a good option to running with the lid on.

 

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Discussion Starter #3
Pull the air box lid off and run it. See how it sounds then. I run Uni vents, have run them in all my air boxes since the 80's. Outerwears also makes a good option to running with the lid on.

Runs weird even removing the lid entirely.

Update: Duct taped the holes back up and installed everything back to stock. Bike still runs weird and I did notice it's sluggish down low and has a stumble at full throttle especially when hitting bumps at full throttle. When I pull the clutch in after the high rev stumble, the bike takes a few seconds to recover to smooth idle.

Went to order a new airbox lid and happened to look at the part that the air filter goes over. Looks like that part is supposed to have about 1/4 inch of foam that seals up against the intake. Mine has zero, nada, zilch of that foam, basically has what looks like the dark glue that holds the foam on. Link to air filter guide

It has ran fine since I got the bike in September, but is it possible I have enough of an air leak from the poor seal to cause these issues all the sudden?
 

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Yes
If you put holes in the lid, remove the lid, change the air filter, or the exhaust, you are going to have to rejet and adjust the carbs.
And, if the filter doesn't seal, then the engine is sucking in more air and is leaner.
It's also going to sound different and be louder.
 

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Discussion Starter #5
Update

Installed the new air filter guide with the proper amount of foam to seal against the intake, and installed a new airbox lid and it runs perfect. I feel like the air filter was just kind of bouncing around and causing most of the issues. Not even gonna jack around with removing the lid as it seems like a lot of trouble for very little to gain, and potentially could lead to a devastating failure.
 

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Update

Installed the new air filter guide with the proper amount of foam to seal against the intake, and installed a new airbox lid and it runs perfect. I feel like the air filter was just kind of bouncing around and causing most of the issues. Not even gonna jack around with removing the lid as it seems like a lot of trouble for very little to gain, and potentially could lead to a devastating failure.
Oh no, there is Alot to gain by removing the lid and jetting accordingly, with no adverse effects.
But, glad you got it fixed.
 
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