[jmcookesq]

Sorry if this is old news but didn't find it when I searched. I was just at the Vintage Bike show here in Raleigh and all the guys had the same universal K&N filter on their bikes (and these had the same carbs as the CX). Does anyone know which part number this K&N filter is? Thanks.

 

[Blindstitch]

Are you talking about the airbox filters or pod filters?

 

[WisconsinCX]

Stick with the stock airbox and paper filter. The carbs, airbox, and paper filter are all designed to work together to create the correct vacuum. My experience is that leaving it the way Honda designed it was always best.

 

[Bryan]

Although I have no specific basis for my fear of K&N air filters, the fact that K&N touts better airflow always leaves me feeling that they must not filter as well as paper elements.

 

[jasonh]

My experience is that leaving it the way Honda designed it was always best.

So do you use ATF in your forks still?

 

[nolavox]

this is the one I use HA-0700



http://www.knfilters.com/search/product.aspx?Prod=HA-0700



oil filter pn is- KN111



J

 

[jmcookesq]

Are you talking about the airbox filters or pod filters?

I am asking about pod filters. I have removed the airbox. (Amazingly, I can hear the "Gasps" from fellow members through the internet!) Thanks.

 

[Blindstitch]

Should be 54mm. Have fun rejetting.

 

[WisconsinCX]

So do you use ATF in your forks still?

So your telling me you know more than the Honda engineers that designed the intake system of all the Hondas that use CV carbs?

If you know so much why don't you go over the the DOHC forms and inform 99.9% of the people that have tried K&N then gone back to paper once they realized that their bikes run like crap with the K&N that you can help them cure all the problems K&N cause.

 

[Trickster]

So your telling me you know more than the Honda engineers that designed the intake system of all the Hondas that use CV carbs?

If you know so much why don't you go over the the DOHC forms and inform 99.9% of the people that have tried K&N then gone back to paper once they realized that their bikes run like crap with the K&N that you can help them cure all the problems K&N cause.

Not to claim that "I" know more than the Honda engineers, but perhaps new technological advancements of any sorts have



been made in many areas since the inception of the CX/GL.



This is where I think the OP was going with his question.



BTW I am not a fan of K&N in any motorized vehicle, been down that thread at length before.



Like I said tho, many improvements/upgrades can be made to these 30yr old+ machines (actual fork oil, electric fans, fuses,etc.)

 

[senile_seinen]

Engineering is the art of compromising cost and technology to get an acceptable result.



Good engineers design machines like our CX/GLs They were pretty cheap in the day for what you got, and have obviously proved to be both fun and durable.



But consider the implication of my first sentence: technology is not static - it changes over time. Therefore, ideal solutions change over time as well. - that's why a cheap 2010 bike is probably a better motorcycle to actually ride than a good 1940 bike.



That said, you had better be willing and able to re-do all the affected engineering if you want to change something basic in a complex system and get a result as good as what was there before. Most people aren't up to this. Many more believe that they are than actually are. That's why so many modification jobs end up running like crap/dangerous/covered in dust in a corner: not everybody was cut out to be a mechanical engineer.



Our engines are air pumps. Everything in the system was designed to work together as a set. If you change the mufflers, air box, H-box, or any combination thereof, you change the volumetric efficiency of the system, probably in complex and unexpected ways.



One problem we're all dealing with is that the cam grind is what it is, and it was designed with expectation of certain amounts of exhaust resonance and backpressure and intake resonance and restriction. Since there were no aftermarket cam grinds for the CX, you're left unable to alter the pumping parameters of the engine to deal with changes in the plumbing. That's why the fuel economy goes to hell with straight pipes, with pods, or both.



This sort of plumbing mod makes a lot of sense for Jim running at Bonneville - he's running the engine beyond the stock redline, so pumping efficiency goes well below stock values at cruise RPM. Increasing the flow efficiency of the intake and exhaust can do nothing but help as long as his engine is above 8000 RPM or so. It probably runs like a dog at 3500, though.



That's the difference between hot rodding and road vehicle engineering - the compromises. Jim doesn't care that the bike is unrideable at 30 MPH on the street. He cares a whole lot that it is fast and stable on the salt. Imitating what he did with your street bike will probably not get you what you're looking for, no matter what you're looking for.

 

[Cruiser]

Geez,



I've had K&N filters in a variety of vehicles from a 1955 Chevy to my current crop of

vehicles which include a 1998 Chrysler Sebring convertible, 1999 Pontiac Grand Am, 1992

GMC Suburban, 2001 Ford E350 Motorhome, and of course my 1983 GL650 Silverwing. Every

one of those vehicles, during which I've put on a huge amount of miles driving in all

conditions have resulted in a minimum of 10% or greater miles to the gallon and a little

more power (not a lot). Also being able to clean and reuse them is a benefit also.



You have to think about those engineers. Like any other manufacturer of vehicles with wheels

and motors, they would have had at least some minor tolerances to deal with the variety of

conditions, both external to the motor as well as internal. Weather conditions, dust, wear

and tear, not to mention all the different mods that people love to put on vehicles. Not to

mention all kinds of different amounts of stress on the engine by road conditions and grades,

weather, and of course people that tend to have just two functions with the motor. Either off

or redline.



I just don't think the K&N air filters do not have enough of a impact on a motor to

cause any issues or damage. Oh, and I've gotten as much as 55 with me and the wife

as almost 60 to the gallon with the bike and plenty of power.

 

[senile_seinen]

I'm running a single oiled foam filter in the stock airbox with the stock pipes. I think my fuel economy might have gone up from the paper filter as well, although it's quite possibly because the stock filter was pretty dirty. Another possibility in both cases is that the bike is running leaner in midrange, which is quite possible with a freer-flowing air cleaner than the system was designed for. I do know that it's colder-blooded than it used to be, which is also suggestive of it being leaner.



Again, it's all about the compromises. If you are willing to accept the change in behavior, it may be a good thing. The point is that you have to be aware that there *will* be a change in behavior.

 

[Shep]

Ditto what Senile Seinen say.



My old Norton Years a go had Mono-bloc carb with a Bell-mouth/Throttle slide operated so NO filter.



The CX/GL bikes use constant velocity carbs that rely on a certain amount of controlled restriction including the Air-filter/Air-box and Engine Breather system.The K&N filters may well be an improvement but I would be checking my plugs and mixture to allow for better air-flow if indeed they can deliver this.



I've also seen posted that removing the Air filter can improve mileage.I tried this on my Spare CX and it didn't seem to do much except make starting bad even after adjusting the mixture.I didn't really give it long enough tho' so it was not a fair test.

 

[Cruiser]

Well, I've got serveral thousand miles on my bike. I'll check the plugs for color,

but think you would need to run a bit longer to see the results.

 

[wightegi]

Sorry if this is old news but didn't find it when I searched. I was just at the Vintage Bike show here in Raleigh and all the guys had the same universal K&N filter on their bikes (and these had the same carbs as the CX). Does anyone know which part number this K&N filter is? Thanks.

My GL has a K&N filter in the air box runs well and the fueling is ok looking at the plug colour.I have a lot of atf so what did I use when I changed my fork seals,

still easy to change in the fuure.

 

[SteveinPA]

I run a K&N air filter in the stock airbox, and the only problem with it is I don't get around to cleaning it when I should. I have thought of going back to paper filters but the time spent running to pick one up is more time than cleaning and re oiling the K&N would be. My bike runs like a top with the K&N. I did just switch back to ATF in my forks though, after running 20 wt fork oil for the last 16,000 miles or so. I like the smoother ride the ATF provides over the 20 wt. for now. I should probably change my plugs someday too. I have had the same set of iridium's in the darn thing for over 20,000 miles.

 

[rogerb]

In my experience I find that the K&N filters allow a higher flow rate simply by not filtering as well as a stock paper filter. Many tests have borne that out. I'll stick to the stock paper filter to protect my GL650i's engine.

 

[nolavox]

Engineering is the art of compromising cost and technology to get an acceptable result.



Good engineers design machines like our CX/GLs They were pretty cheap in the day for what you got, and have obviously proved to be both fun and durable.



But consider the implication of my first sentence: technology is not static - it changes over time. Therefore, ideal solutions change over time as well. - that's why a cheap 2010 bike is probably a better motorcycle to actually ride than a good 1940 bike.



That said, you had better be willing and able to re-do all the affected engineering if you want to change something basic in a complex system and get a result as good as what was there before. Most people aren't up to this. Many more believe that they are than actually are. That's why so many modification jobs end up running like crap/dangerous/covered in dust in a corner: not everybody was cut out to be a mechanical engineer.



Our engines are air pumps. Everything in the system was designed to work together as a set. If you change the mufflers, air box, H-box, or any combination thereof, you change the volumetric efficiency of the system, probably in complex and unexpected ways.



One problem we're all dealing with is that the cam grind is what it is, and it was designed with expectation of certain amounts of exhaust resonance and backpressure and intake resonance and restriction. Since there were no aftermarket cam grinds for the CX, you're left unable to alter the pumping parameters of the engine to deal with changes in the plumbing. That's why the fuel economy goes to hell with straight pipes, with pods, or both.



This sort of plumbing mod makes a lot of sense for Jim running at Bonneville - he's running the engine beyond the stock redline, so pumping efficiency goes well below stock values at cruise RPM. Increasing the flow efficiency of the intake and exhaust can do nothing but help as long as his engine is above 8000 RPM or so. It probably runs like a dog at 3500, though.



That's the difference between hot rodding and road vehicle engineering - the compromises. Jim doesn't care that the bike is unrideable at 30 MPH on the street. He cares a whole lot that it is fast and stable on the salt. Imitating what he did with your street bike will probably not get you what you're looking for, no matter what you're looking for.

Well Put... As a matter of fact. This is the best synopsis of the issue I've seen to date. being unable to increase the engines ability to effectively pump more air and fuel in and out... means nothing more than unburnt HP/fuel out the back end....

 

[senile_seinen]

Yep, that's exactly what is happening when people report a drop in mileage after going to straight through pipes with no H box - the backpressure in the exhaust system has decreased, which means that the exhaust valve is now staying open longer than it needs to to purge the cylinder. Because it's a pretty high-performance engine, there's a lot of overlap in the cam grind. Result: unburned mixture goes right out the exhaust pipe. This problem should go away at high RPM, but who cruises above 8K long enough to notice?



Individual pod intakes have a milder variation on this problem: because the intake flow is so variable on a single-cylinder engine (yes, you have two single-cylinder engines with a common exhaust system as far as the plumbing is concerned), you can get a lot of what is called spit-back on the intake side at some RPM, but not others. One of the functions of the stock airbox is to capture the fuel-air mixture that otherwise would have sprayed the inside of the air filter and let it be consumed on the next intake stroke.