Going Filterless

[KRS1]

Has anyone ever had any documented bad side effects from running without an airfilter? Yes i know its not good, but have you ever personally ever broken down because of it? Scored a cylinder, clogged a carb, holed a piston, ruined a valve seat etc...?

No heresay please, just personal experience and length of time you ran without it.

[karlos]

I had run an old MkIII Escort with a set of twin DCOE carbs filter-less for about 8 hours (spread over the course of a few days)<br>No reported loss in compression BUT i was running the car on damp roads, i doubt i would have taken the risk out here in Thailand during the dry season.<br>As you clearly understand it's not ideal and could cause irreversible damage to the bores.<br>What vehicle do you intend to do it on, if it's a carb fed scooter you'll end up running lean and the lean condition could end up causing serious damage too.<br>

EDIT, just remembered i used to race Mini Motos back home for a while (2000 pound units, proper ones) The K&N filter i was using on it would often popped off a few times and i race all day not knowing i had no filter!

Being such a small bike and being able to dismantle the whole engine in 15mins i can report that minor scores were evident after the third time so i invested in some silicone and fixed the fault with the filter's mounting point and honed the bore and replaced the rings.

Edited October 30, 2011 by karlos

[thaicbr]

No reports. because i'm not dumb enough to run an engine in Thailand with out an airfilter.

[KRS1]

No reports. because i'm not dumb enough to run an engine in Thailand with out an airfilter.

Then there's no reason for you to reply.

[KRS1]

I had run an old MkIII Escort with a set of twin DCOE carbs filter-less for about 8 hours (spread over the course of a few days)<br>No reported loss in compression BUT i was running the car on damp roads, i doubt i would have taken the risk out here in Thailand during the dry season.<br>As you clearly understand it's not ideal and could cause irreversible damage to the bores.<br>What vehicle do you intend to do it on, if it's a carb fed scooter you'll end up running lean and the lean condition could end up causing serious damage too.<br>

EDIT, just remembered i used to race Mini Motos back home for a while (2000 pound units, proper ones) The K&N filter i was using on it would often popped off a few times and i race all day not knowing i had no filter!

Being such a small bike and being able to dismantle the whole engine in 15mins i can report that minor scores were evident after the third time so i invested in some silicone and fixed the fault with the filter's mounting point and honed the bore and replaced the rings.

Thanks for the info. Just ran some test and upped the jet sizes from 38 to 42 and 118 to 122, (may need to still go higher for both) clip in 3rd position on alternative taper and difference is like night and day. Bike is suffocating with stock filter. Carb is 31.95mm inlet mouth, 29.45mm venturi (OEM 26mm) , downpipe straight through. Air filter is restricting, need to find an alternative.

Edited October 30, 2011 by KRS1

[karlos]

I had run an old MkIII Escort with a set of twin DCOE carbs filter-less for about 8 hours (spread over the course of a few days)<br>No reported loss in compression BUT i was running the car on damp roads, i doubt i would have taken the risk out here in Thailand during the dry season.<br>As you clearly understand it's not ideal and could cause irreversible damage to the bores.<br>What vehicle do you intend to do it on, if it's a carb fed scooter you'll end up running lean and the lean condition could end up causing serious damage too.<br>

EDIT, just remembered i used to race Mini Motos back home for a while (2000 pound units, proper ones) The K&N filter i was using on it would often popped off a few times and i race all day not knowing i had no filter!

Being such a small bike and being able to dismantle the whole engine in 15mins i can report that minor scores were evident after the third time so i invested in some silicone and fixed the fault with the filter's mounting point and honed the bore and replaced the rings.

Thanks for the info. Just ran some test and upped the jet sizes from 38 to 42 and 118 to 122, (may need to still go higher for both) clip in 3rd position on alternative taper and difference is like night and day. Bike is suffocating with stock filter. Carb is 31.95mm inlet mouth, 29.45mm venturi (OEM 26mm) , downpipe straight through. Air filter is restricting, need to find an alternative.

Sounds like some serious tinkering, what bike is it?

i was playing around with the VFR i used to have earlier this year but never really noticed much difference other than getting rid of a mid range flatspot that VFR's suffer from.

A assume as you are tinkering with a scooter that has been set up to be pretty ECO Friendly from the factory or something that wasn't intended to be an all out sports bike from the start to see 'night and day' differences?

As for the dumb comment, yes it's not a good idea to remove the airfilter but he was fishing for some informative posts from 'dumb' people like me

I guess the guys who run their FIA Top Fuel Dragsters (yes granted for 10 seconds at WOT before rebuilding) are dumb too

[KRS1]

It's just a little old CBR 150, just trying to see what can be done with external modifications before cracking it open.

Cams and reshimming are next, but i have to figure out what valve clearances are best for non OEM cams. Pretty sure they're going to need more clearance since the ramp length is different on the lobes. That's going to be a really painful trial and error process im not looking forward to.

[bbradsby]

I just washed my NSR-150sp's stock foam filter after maybe 1000 Km of BKK driving, as the bike was beginning to load up from running rich - and the backwash was black as night with dirt. If you understand that dirt is degraded minerals, ok, with some organic materials depending on where you are, youre basically thinking about running sandblast media through your engine to gain some more power.

It may backfire on you for more than the obvious reason of rocks in your cylinder/piston interface. As the intake airbox is tuned to the resonance of the exhaust system to develop an optimum torque curve, messing with the tuned whole by removing the intake airbox [resonating chamber] of a modern sportbike like yours will probably just cost you useable power. But, hey, run an experiment and see what the effect is. My guess is better power at the very top of the rev range, at a detriment to low to mid RPM power. On a roadrace bike, that may work. On ths street, I wouldn't think the cost/bene ratio would be optimum unless you like racing launches and shifting only at redline.

Better to get a K&N of sufficient size to cover the air volume you're pumping, using the stock airbox if its a modern sportbike - engines are nothing more than air pumps with a spark plug and petrol thrown in for fun!

Edited October 30, 2011 by bbradsby

[wantan]

I was going with filterless cigarettes for some time and i can confirm for sure it is NOT GOOD without filter!

But seriously:

How can someone for sure confirm that the engine broke down because there was no airfilter? Or asking different: What do YOU think is the use of an airfilter?

Air filter is restricting, need to find an alternative.

Alternative 1: No filter by risking a broken engine

Alternative 1: Something like K&N

And of course you can reduce the loss of power from the airfilter by using PURE benzine

[KRS1]

I just washed my NSR-150sp's stock foam filter after maybe 1000 Km of BKK driving, as the bike was beginning to load up from running rich - and the backwash was black as night with dirt. If you understand that dirt is degraded minerals, ok, with some organic materials depending on where you are, youre basically thinking about running sandblast media through your engine to gain some more power.

It may backfire on you for more than the obvious reason of rocks in your cylinder/piston interface. As the intake airbox is tuned to the resonance of the exhaust system to develop an optimum torque curve, messing with the tuned whole by removing the intake airbox [resonating chamber] of a modern sportbike like yours will probably just cost you useable power. But, hey, run an experiment and see what the effect is. My guess is better power at the very top of the rev range, at a detriment to low to mid RPM power. On a roadrace bike, that may work. On ths street, I wouldn't think the cost/bene ratio would be optimum unless you like racing launches and shifting only at redline.

Better to get a K&N of sufficient size to cover the air volume you're pumping, using the stock airbox if its a modern sportbike - engines are nothing more than air pumps with a spark plug and petrol thrown in for fun!

Not thinking about running without a filter forever

Airbox has already been retuned to match exhaust.

[BSJ]

Over a period of 45 years, in the early years, I have run many bikes without air filters, as supplied by the manufacturer. Usually clunkers that don't have a lot of money value. My dad, after suggesting to buy a proper filter, suggested covering the carby inlet with fly wire to keep out stones and gravel, which I did. Never had a serious problem.....

[KRS1]

Over a period of 45 years, in the early years, I have run many bikes without air filters, as supplied by the manufacturer. Usually clunkers that don't have a lot of money value. My dad, after suggesting to buy a proper filter, suggested covering the carby inlet with fly wire to keep out stones and gravel, which I did. Never had a serious problem.....

Thank you for sharing your experience, there is the wire mesh screen from the original filter in place right now, about twice as small as mosquito screen mesh.

[cdnvic]

Removed several posts and one poster over a rather silly fight.

[mezcal]

I bought a Keihin CR38 Special carb for my Yamaha SR. It says "For racing tracks only" on it and it is supposed to run with an open cone, no air filter. That's the way I've been riding around for about 5 months until one day on a bike trip, the engine just died and wouldn't start anymore. After checking spark plug and gas flow I realized it must have been the carb. Opened a big bolt underneath the carb to let the petrol come out, closed and bike started on the first kick.

Next move: get a K&N filter!

[KRS1]

I bought a Keihin CR38 Special carb for my Yamaha SR. It says "For racing tracks only" on it and it is supposed to run with an open cone, no air filter. That's the way I've been riding around for about 5 months until one day on a bike trip, the engine just died and wouldn't start anymore. After checking spark plug and gas flow I realized it must have been the carb. Opened a big bolt underneath the carb to let the petrol come out, closed and bike started on the first kick.

Next move: get a K&N filter!

Thanks, but im wondering if it was caused more by sediments in the gas tank. Have a fuel filter? I opened the carb yesterday and there was rust in the bowl, so i guess the screen cylinder connected to the fuel valve isn't straining very good. Bike stalled twice in 3 months do to dirty gas. Freaking choke cylinder's been giving me grief on my other bike too until i figured out there was grime in the choke cylinder and wouldn't allow the choke plug all the way back down.

[mezcal]

There is a filter on the petcock inside the tank and I installed another one in line between the petcock and the carb. They both looked clean last time I checked, so I don't think it came from the tank.

An open carb might be OK when you're racing and need to squeeze out every last bit of power, but on Thai roads it's just not a good idea I think.

[KRS1]

Gotcha, came across some material today that should serve well in filtering the air enough to keep out the more damaging stuff, cut it up today to fit and will test the flow properties tomorrow.

[wantan]

Gotcha, came across some material today that should serve well in filtering the air enough to keep out the more damaging stuff, cut it up today to fit and will test the flow properties tomorrow.

Let me guess: An old sock?

[bbradsby]

Gotcha, came across some material today that should serve well in filtering the air enough to keep out the more damaging stuff, cut it up today to fit and will test the flow properties tomorrow.

What filter material are you considering? I need a replacement for my orig foam filter on the NSR - if its a gauze or light filter matrix, fit an armature so it doesnt get sucked into the engine.

[bbradsby]

There is a filter on the petcock inside the tank and I installed another one in line between the petcock and the carb. They both looked clean last time I checked, so I don't think it came from the tank.

An open carb might be OK when you're racing and need to squeeze out every last bit of power, but on Thai roads it's just not a good idea I think.

petcock has a screen, not a filter, and fine rust & dirt will pass. ask me how I know :] - an inline filter downstream has caught lots of junk the petcock screen passed. Time to Kreem [fuel tank interior epoxy sealer] my tank. Anybody know where to get it in BKK?

[KRS1]

Gotcha, came across some material today that should serve well in filtering the air enough to keep out the more damaging stuff, cut it up today to fit and will test the flow properties tomorrow.

What filter material are you considering? I need a replacement for my orig foam filter on the NSR - if its a gauze or light filter matrix, fit an armature so it doesnt get sucked into the engine.

Why not just get a new foam filter from Honda?

The stock filter has a 3 layer screen and expanded mesh plate installed, then has a corrugated paper element over it. The screen and expanded mesh has been left in place.

If the experiment works tomorrow i'll send you a PM.

[KRS1]

Gotcha, came across some material today that should serve well in filtering the air enough to keep out the more damaging stuff, cut it up today to fit and will test the flow properties tomorrow.

Let me guess: An old sock?

No, rolling papers from your mama's stash.

[KRS1]

Experiment with the new filter material worked out excellent, almost flows as good as without a filter. Slight drag, but after 5k can hardly tell the difference between running without a filter and the new element.

I want to do atleast 1k kilometers on it before i release what the material is that was used, just incase the material breaks down in composition. But for right now i can tell you it's less flammable than paper, more tear resistance than paper and gauze, resist petroleum fuels, and is synthetic (i think).

Right now there is one layer, will test with 2 layers tomorrow for better filtration and check flow properties.

Before anyone tells me, yes there is a light coat of oil i applied to it. (WD40 actually)

Ok, stage 1 mods are finally done, im taking a break now, if anyone needs jets in sizes (slow) 38, 42, 45....... (main)118,120,125, 128, 152...let me know - 600 baht for all of them, testing is over and don't need these any longer. They fit Keihin slide carbs with a "P" model number eg; PE, PWK, etc....Also have one 38 slow for a Phantom, which has the same threads but shorter than the others. 200 baht for this one though, i had to order it from Honda.

Edited November 2, 2011 by KRS1

[wantan]

I want to do atleast 1k kilometers on it before i release what the material is that was used, just incase the material breaks down in composition. But for right now i can tell you it's less flammable than paper, more tear resistance than paper and gauze, resist petroleum fuels, and is synthetic (i think).

I told you it is ......... a nylon sock with a bit WD40 on it.

But tommorow KRS1 takes the left AND the right sock and calls it a "double layer filter". Are you as curious as i am?

[KRS1]

Welcome to my ignore list Wantan.

[cdnvic]

I'm really getting tired of having to police this forum as much as all the others put together. Learn to get along, and stop with the potshots at each other or anyone involved will lose their posting rights.

[mezcal]

I want to do atleast 1k kilometers on it before i release what the material is that was used, just incase the material breaks down in composition. But for right now i can tell you it's less flammable than paper, more tear resistance than paper and gauze, resist petroleum fuels, and is synthetic (i think).

I told you it is ......... a nylon sock with a bit WD40 on it.

But tommorow KRS1 takes the left AND the right sock and calls it a "double layer filter". Are you as curious as i am?

I'm sure there were people criticizing Burt Munro when he made his own pistons and cut off tire rubber to go faster, but look where it got him...

When you love your bike and love working on it you will definitely make some bad decisions from time to time, but hey, they're part of the learning process. I'm like that and I respect others like that.

[wantan]

I want to do atleast 1k kilometers on it before i release what the material is that was used, just incase the material breaks down in composition. But for right now i can tell you it's less flammable than paper, more tear resistance than paper and gauze, resist petroleum fuels, and is synthetic (i think).

I told you it is ......... a nylon sock with a bit WD40 on it.

But tommorow KRS1 takes the left AND the right sock and calls it a "double layer filter". Are you as curious as i am?

I'm sure there were people criticizing Burt Munro when he made his own pistons and cut off tire rubber to go faster, but look where it got him...

When you love your bike and love working on it you will definitely make some bad decisions from time to time, but hey, they're part of the learning process. I'm like that and I respect others like that.

I pay my full respect for this airfilter research too. The old sock is a trick from my own tuning attempts when i was younger (we didn't had such things like moskito net or similar). Just remove the airfilterbox and put the sock over the open carb end to keep insects and some other things out of the engine. I am not sure anymore if it was nylon or wool. But for sure i had no WD40. And the effect was amazing loud