Any issue with running a backfire screen?

[Chadx]

I have a 2004 KTM 525 EXC and just finished my modded airbox. The previous owner cut out the backfire screen (poorly and I'm tired of pricking my fingers) from the filter carrier. Since I'm told prefilters are touchy to backfires, I was about to order a new, unmolested filter carrier with backfire screen in place just in case it helps a bit. Before I do, any reason not to? No issues with backfire screen icing up? I imagine if there is, there are bigger issues, but just checking. Do most of you run your backfire screens in place? Thanks.

 

[DieselTwitch]

I think they are a must! When your filter get clogged with snow, and make no mistake... It will. The screen prevents it from getting sucked into then intake.

 

[Chadx]

I'm building a basket wire support so hopefully collapse won't be much of an issue, but I guess best to have a second line of defense. Glad to hear there are no issues running a backfire screen. I'll order up another on this morning.

I'm building a basket rather than running an un-oiled foam filter. Didn't want to deal with the occasional caking issues when the prefilter presses against the foam filter.

I plan to do a write up and photos of my airbox mod. That year KTM has a three piece airbox and I simply removed the middle section. Kept the rear section only because I needed a place to mount my battery. I had bought a Boondocker prefilter/basket and silicon intake adapter hosed, etc. but won't be using those. I couldn't get it all to fit nicely and still fit the battery in there. Guess they'll go on the snowbike swap meet once I figure out how much I have into them (I tried to not pay attention. Ha. That stuff is expensive).

 

[bdoe22]

screen problems

I have seen a number of issues related to running just a filter cage/screen with no air filter. The resonance can weaken the screen and will cause it to fail....ending up in the intake or even worse, stuck in the intake valve!

 

[mtn-doo]

If you remove the back fire screen you need to make a "spring wire cage" like in this pic. It holds your filter in a balloon shape and allows for maximum area for filtration. Even more square inches than a pod. We have been running this on our bikes and it has been the best set-up to date. Bottom of the air box gone, zero snow in the air box, clean filter all day, and stock intake boot tuned for the best engine performance. We spent the last few days demoing in some challenging conditions. Spanish Peaks, 16 above zero, deep pow, perfectly clean and peak performance all day. The bikes with issues we pulled the filter and the back fire screen was totally glazed over, and the air box filled to the top with dry pow. It is a VERY FINE screen. We heated it up, cleaned it and re-installed on 3 different bikes. Just some FYI info. You don't need to have air box snow issues.

 

[Jon Mutiger]

I'm on my second backfire screen as my old one was ripping itself apart. I don't think my bike ate much fine wire.. But it did eat some.

With that said, I gotta get me some of that memory wire and make a pillow for the pre-filter. Where do you get that wire?

Jon

 

[Chadx]

Interesting on the backfire screen deteriorating and breaking up. The fragments on my old stock one, left over from the previous owner cutting it out, seemed pretty course. Maybe he cut it away after it failed. Guess I'll debur it the best I can and not bother with running a new one with a screen since I was building a basket, to hold out the prefilter, anyway.

mtn-doo, that is very similar to what I'm building to support my prefilter. Rather than the middle ring, I was going to attach the wire to one side, loop across the middle, then down and attach to the other side. Repeat four or five times with maybe winding each wire around the previous loop, in the middle, so they don't slip. I like how you did the ring in the middle. Do you seat that ring down on the post or let it float up above? Saw that you have the hole in the middle of the prefilter so wondering if you use the stock air filter retainer or just cover the hole in the prefilter.

 

[mtn-doo]

I'm on my second backfire screen as my old one was ripping itself apart. I don't think my bike ate much fine wire.. But it did eat some.

With that said, I gotta get me some of that memory wire and make a pillow for the pre-filter. Where do you get that wire?

Jon

Hi Jon, hobbylinc.com it is the .032 diameter.

 

[mtn-doo]

Interesting on the backfire screen deteriorating and breaking up. The fragments on my old stock one, left over from the previous owner cutting it out, seemed pretty course. Maybe he cut it away after it failed. Guess I'll debur it the best I can and not bother with running a new one with a screen since I was building a basket, to hold out the prefilter, anyway.

mtn-doo, that is very similar to what I'm building to support my prefilter. Rather than the middle ring, I was going to attach the wire to one side, loop across the middle, then down and attach to the other side. Repeat four or five times with maybe winding each wire around the previous loop, in the middle, so they don't slip. I like how you did the ring in the middle. Do you seat that ring down on the post or let it float up above? Saw that you have the hole in the middle of the prefilter so wondering if you use the stock air filter retainer or just cover the hole in the prefilter.

I used to make a wire arch over the top like you are saying. I just refined it for customers bikes with the large fender washer. Yes, the retainer goes through the pre-filter hole and through the fender washer then into the center post. Everything is tied together and nice and symmetrical. You need to Velcro the pre filter and underside of the plastic cage. I use 3M adhesive Velcro. I cut 8 small patches and put them evenly spaced around the filter and the underside of the cage. The filter then curls around the edge of the cage and sticks underneath, all the way around. That prevents the filter from sliding up in spots. Nice tight seal, all the way around.