83 XL600R - help with air box delete

Just wondering if anybody has personally modded their air intake.  I have seen XL's with fairings removed and the air box removed, with 2 K&N mini cone air filters strapped directly to the back of the carbs, but this is only from pictures.  Is it that easy?  Do I need to cut a hole under the rear fender to force more air in?  Do I need to re-jet after this?  Any help would be very much appreciated, looking for fall/winter projects.  Also interested in removing the crankcase blow back emission system if anyone knows about that.  I've seen pictures of that as well with a K&N filter in place of the emissions system.  The problem with that is the K&N filter has a line in and line out, where as the OE system has line in, line out, and a drain.  Any know how?  Here are some pics of the bike now.  Just put the full XR's only exhaust on, cleaned up some rust on the swing arm, painted the kick stand, and waiting on new mild knobbies to be mounted (hopefully today); just some basic stuff without having to crack the motor open.  



photo 1.JPG

photo 2.JPG

photo 3.JPG

photo 4.JPG

photo 5.JPG

Removing the airbox will absolutely change the power band for the worse, especially if you go with pod airfliters

You need that long venturi and still air box for proper running.

If you do not care about performance, put the pods on, they look good.

Proper carburation depends on a smooth flow of air. The air box and air boots smooth out the air. Pods are fairly abrupt and the 'signal' provided to the slow and main air jets will not be even, causing poor running. You could tune them to work but only at specific points and not over a complete range.

You can remove the crankcase vent line to the air boot but you will want to run it into a catch can to deal with drips that'd normally be consumed by your engine.



If you run the pods and succeed in jetting it properly it will eventually die a death by dirt ingestion.

I think on a big bore you want to focus on low end torque, because they are not capable of the higher RPMs of a 250 or smaller. That being said, dual element Uni-pods keep the dirt and water out. You can wake up a sleepy engine with good airflow in and out. My SP was a pig when I brought it home, now the front end comes up hitting 3rd gear hard. Stock air box did not lend itself to modification.


In the 80's 3 of us were riding along a foot trail by a drainage ditch, the trail went around a fallen tree and onto the steep slope to the ditch. Bastid in front with new knobbies walked right around the tree, me and the other guy swamped our bikes. I took off my pod, wrung it out, rinsed with some gas, put a little motor oil on it and started right up. Other fella with an airbox and stock filter got the rest of my qt of oil and we spent an hour getting his bike started. Swamped mine when it had the stock filter and I was out for a "short" ride home, and it was a long push home.

OP will never be back

OP will never be back


Are you clairvoyent?

OP will never be back

Why is that?  I took the advice of the majority on this one, I didn't think I needed to further comment.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Similar Content

    • By Sammy_1101
      Hi Guys,
      So I recently bought a 1997 XR400. I've done some research into getting more power through some basic mods and rejetting the carbs. Though all of the ones I've found have been for post 98 XR400s so the stock carb set up is a lot different. Usually people are opening up the airbox, exhaust ect. ect. and Jetting their carbs up to 160/162 for mains around 60 ish (I think) for the pilot. However for the 97 model this is close to stock for the jets.
      So essentially what Im asking (Just to cut to the chase ) Has anyone got a 96/97 (maybe 98, not sure) XR400 and has done these similar mods, and what sort of jetting have to done as a result.
      Thanks in advanced, also its my first post so apologies if I havent done everything correctly.
    • By Jturn
      38MM Cast SmartCarb. Purchased a couple years ago for a yz250. Don't have the bike anymore, and it has been sitting around for about a year. Used, but in fine working condition. You can also purchase a different needle for different bikes, as well as rebuild kits from their website.
      Asking $250 shipped to continental United States. I can arrange other shipping options at the buyers expense.
    • By faizakhtar125
      Hey guys I just bought a bike last night. So the seller said the bike will turn on but then die. We didn't try it because it was really late at night and it was raining (seat was wet). But he said if you bump start it, it will turn on and ride. So what do you think the problem is? I just want to make sure it runs... I probably won't be able to bump start it till Saturday (rain)... It's a four stroke, and I know absolutely nothing about them. Thanks.
    • By knotduke08
      I know this topic has been discussed in the past, but I have not found any options available for the new 2018 bikes. I live and work for a new Beta Dealer (Auburn Extreme Powersports) in California, and we are having a difficult time mapping the RR-S bikes for full FMF exhausts. We have tried contacting Beta Support several times for this issue to no avail, and we typically are given the runaround when transferring to techs and secretaries. From what we can gather, the FMF flash is designed for the RR bikes, but not the street-legal counterparts. Every time we try to install the FMF map onto an RR-S errors occur, and the programmer screen goes virtually blank. We have heard through the grapevine that some are using the RR maps on the RR-S with success, but we have yet to try it, even on our own bikes for fear that it will permanently erase or damage the CDI. Any and all help or suggestions regarding this topic would surely be appreciated! Thanks, Ben.