Help me settle a bet...

[fraze11]

On a GS500F (specifically the >06 F models) adding a K&N drop in air filter is not *necessary* when doing a slip-on and jet.  

[crzydood17]

nothing is necessary except a rejet when doing anything with the intake/exhaust... but a lunchbox/drop in are recommended only because who wants to keep rejeting...

[fraze11]

Keep re-jetting??

From what I've understood/read/been told, the K&N drop in and the stock air filter are about as equally restrictive...its the GS's airbox itself thats the choke point.  I was just trying to save my buddy from dropping ~60 bucks on a drop in when there are better places that money is spent...he is putting on a Yoshi TRS and a jet kit next week.

[crzydood17]

nope K&N drop in is less restrictive than stock filter, the airbox really just reduces sound and keeps out water to a extent, no real restriction at all... you can get restrictors for the k&n filter though so that you don't have to rejet but every mod you do to the intake or exhaust requires a small rejet

[fraze11]

Interesting, thanks.    So in that case would you recommend doing the drop in with the Yosh and jet, and do it all at the same time? or do it with the stock filter?

[crzydood17]

all at once is more documented and stable than individually not to mention you let your new exhaust breath better...

[ben2go]

On a GS500F (specifically the >06 F models) adding a K&N drop in air filter is not *necessary* when doing a slip-on and jet.   

No need for the air filter with the exhaust mods and rejet.If in the future, the air filter is upgraded, another rejet will be required.Most of us do the exhaust and air filter upgrade at the same time so we only rejet once.

[joshr08]

actually if only changing exhaust or air filter no rejet is needed because you cant flow more out then you get in and you cant flow more in then you can get out. 

[BaltimoreGS]

actually if only changing exhaust or air filter no rejet is needed because you cant flow more out then you get in and you cant flow more in then you can get out. 

I thought the exhaust can on a GS was the real bottle neck in the system so even if only the exhaust is changed it will allow the stock intake to flow more air (i.e. operate at full capacity) necessitating a re-jet to avoid a lean condition??

-Jessie

[Big Rich]

Back to the OP: if it's in your favor, then no, a re-jet isn't mandatory ALL the time. Jetting also depends on a couple other factors- especially altitude and air temperature. Is it "likely"? Yes.

If you ride the same bike from Death Valley all the way up to the Rocky Mountains, technically you should jet appropriately.

[NickyNumbers]

Keep re-jetting??

From what I've understood/read/been told, the K&N drop in and the stock air filter are about as equally restrictive.

Just curious, where did you read that?  considering the size of the stock airbox and travel of the intake boot, I'm curious as to where that statement was posted.

[lucky4034]

actually if only changing exhaust or air filter no rejet is needed because you cant flow more out then you get in and you cant flow more in then you can get out.  

So what happens if you current exhaust isn't maximizing the amount of air that can move through your current filter?  Once you change the more restrictive exhaust...won't more air move through your filter now?



If you are going to do a 400$ mod on your exhaust... and then pay for a rejet.... why wouldn't you want to change the filter at the same time and save yourself an extra rejet...  

[ben2go]

Keep re-jetting??

From what I've understood/read/been told, the K&N drop in and the stock air filter are about as equally restrictive.

Just curious, where did you read that?  considering the size of the stock airbox and travel of the intake boot, I'm curious as to where that statement was posted.

That's another one of those false statements that has been made just like a rejet isn't required with an exhaust or air filter change.I've done enough of this over the years to know that there will be running issues without a rejet when an air filter or exhaust upgrade is done.It will cause a lean condition if not rejetted and eventually lead to a burnt valve and/or piston.

[fraze11]

Good info here, thanks!  Just to re-state; I wasnt so concerend about the re-jetting when adding the pipe (I know thats required) ... it was more around should you add a K&N filter when doing the Jet and slip on or will the stock air filter suffice.  I had told him don't bother with the K&N and to use that 70 bucks for some new front springs.  But I do understand that if my buddy does decide to get a K&N drop in (or similar) down the road he will need to re-jet again...