So I bought this hawk used last year and am putting a new air filter in it for the riding season. I have noticed that it has the "plugs" so it is a K&N filter. The bike has M4 exhaust on it as well. I have checked the plugs and they are a nice tan color so I am guessing it was rejetted. Now I ordered an OEM air filter. If I use the OEM filter am I going to have to rejet, or should I use the OEM filter and check the plugs or just leave in the K&N, clean and reoil. The bike does stumble a bit when revving it up in neutral but once moving it seems to accelerate fine except right from 2000 rpm when you crack it the bike wants to stumble before it goes. What filter would you put in?

 

So is that a M4 full system (and if it is you better have a camera and a tape measure handy..... ) or just slip ons?

I would put the stock filter in and see if that cures the problems you are having.....

 

I'm no exhaust expert but I believe they are just slip ons, They were pretty much brand new when I bought the bike and alot newer looking than the piping coming off the cylinders.

 

+1
Although the pull really starts at 3000 rpm. If I drop below 3k, I downshift. And if you whack it open in 1st at 2000 rpm, you better be ready for the front end to come up.

 

has the TPS been adjusted? That and $5 says that it was not rejetted by the PO.

 

I haven't touched the TPS, I researched the mod on here and decided that its not worth it at this point, It seems that people have limited success with it. I think it has been rejetted due to the plug color, absolutly no sign of it being lean.

 

The TPS adjustment made a big difference on my bike. Starts immediately whereas prior is was a chore, idles smoothly with good off idle throttle response. It is an easy fix, you might try it in the event that it will have a positive affect on your bike too. Real good write up in the KB. Plug readings are tricky, depending on how it is done you will get different results. It is an indicator, not an absolute. I like to go by how the engine runs.

 

plug color used to mean more when gas was leaded. Also the superhawk has really expensive plugs because the are specially designed not to foul so just because the color is tan doesn't mean the jetting is right. I like to go by two things does it rev smoothly under different throttle amounts throughout its entire range, and does it get between 40 to 45mpg on the highway. If it does both I leave it alone. All the time and mess jeting for a 1 to 2 hp gain is trivial to me. If I want 2 more hp gain I will get it in weight ratio.

 

you might wanna do a more thorough research relative to the effects of the TPS adjustment, esp with the symptoms you describe. Helps to have another set of hands but is doable solo. With the M4 exhaust, keep the k&n unless you like to waste money, and you would benefit from air mixture adjust (start with 2.25 turns out), shim needles(.40), and a carb sync. PAIR removal. And you'll think you just gotta a new bike. I have a self-made foam oiled filter in mine and cut the flap out of the air box and it runs strong.
I think with your buying a OEM filter and assumming a jet kit,you are likely jumping ahead of yourself. Costs nothing to do the mods that have been demonstrated to improve the majority of the hawks here. So what do you have to lose for a few hours work, esp considering that everything is reversible.