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Backfire Filter
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Posted by: CRSpeedy---------------------

Has anyone bought the back fire filter from Twin Air? Is it worth $230. Has anyone came up with another way to make the back fire screen less restrictive but safe?

Posted by: J.B.426---------------------

I wonder what happened to the Poweflow kit they had for $105 retail? Now that one says it has an inner sealing ring for an extra $125. I think I'm pretty sure I wouldn't get $230 worth of benefit out of that, but that's just me.

As you probably know the wire screen will just snap out. Twin Air has back fire filters, which are fire resistant, that they sell separately now, but I'm not sure if they work on the stock cage. I would consider that if it would work. Of course I'm not really looking for any more performance, it's just fine right now. But it might make cleaning the air filter easier.

Posted by: The Honda Pilot---------------------

What is the purpose of that screen?

Posted by: High Lord Gomer---------------------

If you get a backfire through the carb, it is supposed to keep it from igniting the filter and the hair on your butt.

Posted by: The Honda Pilot---------------------

Now Gomer is this generally a less painfull procedure than waxing?? Or do you suggest burning?

Posted by: lavaman---------------------

Hey J.B. 426, Whaddaya mean by, "the filter screen will just snap out" ? Can ya explain it? TIA....

Posted by: Highbeam---------------------

Have you ever heard of this actually being a problem? I have serious doubts about whether you need this item at all. I have the twin air filter and cage in my XR400 with no backfire screen. I would not pay 1$ for this device let alone 230$. More important to address would be the little spring loaded trap door on the carby.

Posted by: Yogurt---------------------

I say just get a PC Pro Seal for the filter, and a TwinAir Backfire filter, and remove the stock back fire screen. The TwinAir backfire filter will fit the stock cage. At least that's what I'm planning on doing. I'll let ya know how it goes when I do it.

Posted by: Rich Rohrich---------------------

Do you guys honestly believe that the backfire screen is eating some massive amount of horsepower? I know it's probably crazy to ask this but have any of you actually bothered to TEST in some reasonably controlled fashion the difference with and without the screen ?

Posted by: Yogurt---------------------

OK, I just got off the phone with a rep from TwinAir USA. The $105 kit includes the aluminum cage without a backfire screen, and a BackFire filter. The $230 kit, includes a different aluminum filter cage, BackFire filter, and a rubber sealing ring. The $105 kit has the stock size filter cage. The $230 kits filter cage is a different size to ease in installation. So the replacement filters for the $105 kit will work directly with the stock filter cage. But the replacement filters for the $230 will only work with that kit. Hope that answers some questions, I know it answered mine. So I plan on just removing the stock filter screen, and putting on a BackFire filter. Much cheaper than putting out $105 or $230. The BackFire filters go for about $30 at most aftermarket dealers.

Posted by: E-Ticket---------------------

Quote:

Originally Posted by Rich Rohrich

Do you guys honestly believe that the backfire screen is eating some massive amount of horsepower? I know it's probably crazy to ask this but have any of you actually bothered to TEST in some reasonably controlled fashion the difference with and without the screen ?

Rich, I don't think anyone has done any definitive dyno-testing with the BF screen yet. Such as:

= stock filter/bf screen/stock jetting
= stock filter/no bf screen/stock jetting
= stock filter/no bf screen/with jetting
= KTM bf filter/no bf screen/stock jetting
= KTM bf filter/no bf screen/with jetting

Until someone does that -- it's all "my buddy said..."

But I know where everybody is coming from. The first time we took off the air filter off of the wife's 250x --- my first thought on seeing the bf screen was, "...holy crap... how does *any* air get through that..!?"

The backfire screen is made up of a zillion, tiny air holes. Your first impression is that it looks just like a Scott's Stainless Steel oil filter....

That being said, we *might* go to the screenless, Twin Air BF filter ... just to make changing/clearing the air filter easier.
The filter/air box door clearance is a real PITA.....

Cheers! - rb

Posted by: J.B.426---------------------

Quote:

Originally Posted by lavaman

Hey J.B. 426, Whaddaya mean by, "the filter screen will just snap out" ? Can ya explain it? TIA....

I haven't done this but you can bend the tabs out, that hold the screen on the cage, with some pliers and the whole screen will come out.

Quote:

Originally Posted by Rich Rohrich

I also thought it would be of little advantage to remove the screen but after seeing it for myself, I can see how it could be restrictive. It's very fine mesh and two layers at that, certainly a little overkill on Honda's part. But how many people actually NEED more power than these come with off the showroom floor?

Posted by: Rich Rohrich---------------------

Quote:

Originally Posted by E-Ticket

The first time we took off the air filter off of the wife's 250x --- my first thought on seeing the bf screen was, "...holy crap... how does *any* air get through that..!?"

That's what I thought when I got my first YZ400F in 1998. First thing I did was pull the head, carb and subframe off and connect them to the flow bench. After numerous tests with various combinations what was the final conclusion? Wellll, even in it's current 14:1 compression 444cc, 52+ horsepower state my YZF still has the screen and so does my CRF450. Feel free to draw your own conclusions.

Posted by: E-Ticket---------------------

Quote:

Originally Posted by Rich Rohrich

Very interesting-g-g-g.....! hmmmm.....

Truth be told -- our's will most likely stay in place because it's the wife's bike and I *don't* want her to have any *more* power just yet.

Thanks! - rb

Posted by: SFO---------------------

If you have ever witnessed a big single on fire due to a backfire after being flooded, this would seem like an absolutely insane thing to want to do.
Add a bunch of overlap with a lost spark ignition and there is a very real likelyhood of a flaming fart rolling through the intake tract.
The 53hp 444 had the screen in it and our national bike also had it.
The bike I saw burning was a beautiful spondon rotax that the owner had over 25k in.
Carbon fiber burns really quickly too.

Posted by: srellis---------------------

Quote:

Originally Posted by E-Ticket

our's will most likely stay in place because it's the wife's bike and I *don't* want her to have any *more* power just yet.

Quote:

Originally Posted by E-Ticket

The first time we took off the air filter off of the wife's 250x --- my first thought on seeing the bf screen was, "...holy crap... how does *any* air get through that..!?"

The filter/air box door clearance is a real PITA.....

I honestly think we are living in a parallel universe!!! Way too scary!!!

Posted by: E-Ticket---------------------

Quote:

Originally Posted by srellis

I honestly think we are living in a parallel universe!!! Way too scary!!!

Oh yah.... :thumb: - rb

Posted by: PAULRY---------------------

Quote:

Originally Posted by Rich Rohrich

I have not done any tests with the screen removed, but just looking at the screen, I would say there has to be an increase in the flow of air with the screen removed. With more air comes more power. Massive no, but an increase I am sure.

Posted by: Rich Rohrich---------------------

Quote:

Originally Posted by PAULRY

I have not done any tests with the screen removed, but just looking at the screen, I would say there has to be an increase in the flow of air with the screen removed.

There isn't an increase that the engine cares about. Years of playing with a flow bench has if nothing else taught me that rarely does air do anything intuitive, and what looks pleasing to the eye isn't always pleasing to air flow.

Posted by: 380EXCman---------------------

We have been having this same discussion in our shop lately and plan on doing some Dyno tests. But I doubt it will make much of a difference at all. I saw a picture on the net a few years back of a new 520 EXC that had burned to the ground, as a result of a backfire. I will post back with results once we get it done.

BTW, I got to take a spin on a customers CRF450 that we did a topend and kibblewhite valves on and I was pretty impressed. We had a bone stock 04 CRF 450 dyno at 47 hp pretty impressive considering my 04 525 made 48 on our Dyno, now the torque numbers were quite different....

Posted by: PAULRY---------------------

The weekend past I tried one of these Twin Air filters with the cage removed.

On my warm up ride I noticed no difference. On my second ride, when I rode the bike higher in the RPM I could feel a definite difference. The bike accelerated harder from the mid on up.

My conclusion is that the removing the cage makes little difference when riding in the low end part of the power curve, but makes a noticeable difference in the upper mid to top end part of the curve.

I feel that it was a worthwhile purchase.

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Backfire Filter

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