should i cut the air box???

i was wondering how much of an improvement do you gain by cutting the side panel? Right now im uncorked, 180 main, hot cam stage 2, and fmf powercore 4 . Now the question im basically asking is does the power increase justify the added maintenance on the air filter?

I do not understand how you can run a 180 main jet w/o opening the side cover!? Huge difference in flow!!

I was where you're at with 175 main, sea level, 30-40 deg, HRC tip and the opened side cover let the engine rev another 1,000 rpm....and I'm still too rich.


the 180 main gives better midrange pull...and actually the airbox would have no effect on the engine rpm limiter. the only way to get higher rpm is to change/modify the capactor discharge ignition unit. But i would imagine the airbox will give more mid-high end power increase.

What I'm trying to say is that I could not hit rev limiter without opening the air box side cover. The side cover venting gave me 1,000 more rpm but I still haven't bumped the 8,200 rpm limit!

I don't see the point of wringing it out if there's no power to be gained and I am geared 14/45.

More power is gained only by more flow, so more power is more air filter maintenance. If your primary concern is air filter maintenance, then tune and run at low rpms. Use the stock header, replace your hot cam with stock and keep it below 6K rpms. Kinda like a corked XR.

Maybe I should also ask what is your standard air filter maintenance?

i dont know about you but a stock corked up xr650r is like running an xr250 { to me at least} I clean my air filter every 8 hours of riding . {very sandy here}

Any ways i think were are both different type's of rider's and i dont want a muffled xr , but i appreciate your insight. P.S. if you couldnt hit the rev limiter before then there may be something wrong with your bike....a stock even corked bike will hit the limiter if you wring it

I love the power gain. Enough extra air to run one sive bigger pilot & main jet. The cool thing is, I got the power gain without fuel economy loss.

The downside, like you said is cleaning the air filter. I have to now around every 150 miles. Less if I'm riding in a dusty area.

It's a little pricey, but I bought 2 TwinAir Powerflow kits, and 2 extra foams. I can swap filters anytime, even while camping, and then I just wait & clean all 4 filers at once.

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