Conical air filters / jets ??

Dear Forum.

I´m sure this subject has been up before, but I´m having a hard time finding any posts about this specific topic in the forum. So my question is:

I´m thinking of changing my original air filter box out to 2 smaller conical filters on my 1971 commando. I know I´ll have to change my jets but how much?
I have std carbs (930) with std jets installed now.

Main jet = 220
Needle jet = 160

And please let me know if there is other thinks I should be aware of if I change them.



Thanks.

Daniel Christensen

------------------------------------------------------
Ride on..

Norton Commando 750 1971
BSA B40 1968
Kawasaki Z 750

Daniel C said:

Dear Forum.

I´m sure this subject has been up before, but I´m having a hard time finding any posts about this specific topic in the forum. So my question is:

I´m thinking of changing my original air filter box out to 2 smaller conical filters on my 1971 commando.
And please let me know if there is other thinks I should be aware of if I change them.

Thanks.

Daniel Christensen

------------------------------------------------------
Ride on..

Norton Commando 750 1971
BSA B40 1968
Kawasaki Z 750

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Hi Dan, welcome. K&N "rock screens" will allow fine particulate abrasive material to pass through your engine, wearing it out prematurely. Been proven over and over. It's the mechanical equivalent of clubbing baby seals. :shock:

I have a pair of these I ran for a while and saw no need to rejet. As to what's been "proven" about K&n filters (mine were not) K&N would be bankrupt from paying warranty claims if their filters worked that poorly.

Danno said:

I have a pair of these I ran for a while and saw no need to rejet. As to what's been "proven" about K&n filters (mine were not) K&N would be bankrupt from paying warranty claims if their filters worked that poorly.

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How, would one go about making a warranty claim on long term durability with an aftermarket parts supplier? :?: :idea:

I consider this "proof": http://www.billswebspace.com/AirFilterTest.htm

That, and 37 years ago, I witnessed on my own (street) bikes fine particulate in the carburetor intake bellmouths. I've never seen it with paper element or oiled foam, kinda concurs with the lab tests.

JMWO :wink:

I run a Ducati branded K&N filter in my ST3 , it's oiled , I check yearly and so far the trumpets are spotlessly clean , I always give them a wipe because of the pain getting air box off but not really necessary .... do you think all K&N filters are faulty long term as I am using one in the G35 coupe also ...
Craig

I ve run the dual outlet K&N filter on my 930 amals for 40 years. I've tried all sorts of jet combinations out of curiousity. The stock jetting works fine with the K&N filter below



I would believe that the filter that has the highest flow rate also has a lower level of filtration.

Craig said:

I run a Ducati branded K&N filter in my ST3 , it's oiled , I check yearly and so far the trumpets are spotlessly clean , I always give them a wipe because of the pain getting air box off but not really necessary .... do you think all K&N filters are faulty long term as I am using one in the G35 coupe also ...
Craig

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I won't put them on anything, but I know most people never get to the far end of an engine's longevity, hence they see/experience no problems. That said, I bought a brand new TDI VW, rolled ONE MILLION Kilometers on it (621,000 miles), sold it to my buddy, he's still running it. All on pleated paper air filtration media. The oil analysis always confirmed low silica levels. Other enthusiasts with K&N, and other window screen/gauze copies, their oil reports showed very high and (from the lab advice) "cause for concern, check for intake leaks" levels. The only advantage a K&N has, anywhere, anytime, is high speed flow, and then only if the original air filter design was too small/restrictive. Also, the wash, re-oil and re-use thing is nuts, the gauze clumps up leaving big holes. :shock: The chrome end caps on the conicals are pretty... :lol: :mrgreen:

Thanks for the info .... all very interesting ..... guess I better check out these filters .... the coupe , while 12 yrs old is low mileage 105000km the Ducati is at 49000kms all with the K&N filters ...... my Commando makes do with an oiled foam sock ....
Craig

o0norton0o said:

I ve run the dual outlet K&N filter on my 930 amals for 40 years. I've tried all sorts of jet combinations out of curiousity. The stock jetting works fine with the K&N filter below

I would believe that the filter that has the highest flow rate also has a lower level of filtration.

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I have also ran these air filters on my Norton for over 35 years without any problems at all and my motor has had long engine life with no signs of wear caused by air filtration, if they were so bad as some say. K&N would not be around today, my motor has well over 160k and 41 years of hard riding since I brought it new and only rebuilt twice in that time and still running std size conrod bearings and has only been reboard once in that time.

Its like anything on a motorcycle your got to do the maintenance regularly, clean and reoil the filters as well when changing your oil etc etc, as for jetting I went one main higher, but on a stock motor no need to change jets using pod filters, I am now running with PWK carbies for the last 6 years.

Ashley

I have one of the dual K&N filters for a Norton that came on the flood bike. I cleaned it up and re-oiled it with red K&N filter oil and it looks nearly new. I have run K&N and BMC filters in several bikes and zero wear-related problems. Perhaps someone is running theirs dry and it's not performing up to snuff.

A few years back , Danny Smith rode his 47 Rapide from Vancouver to Tierra Del Fuego and home, about ten thousand miles. Because much of the South American portion of the trip was on dusty gravel roads, he had a look at the bores afterward. They were in perfect shape, no scoring, his honing marks still visible. He runs K&Ns on that bike, always has.
Glen

Typical 1 or 2 jet sizes up but possibly no change.

You have only covered part of the carb operating range. The main jet comes into play mainly at the wider throttle settings but does have some influence lower down. You say you have a 160 needle jet. I guess you mean 106. There is needle position to fiddle with and slide cutaway. The only way to find out properly is on a rolling road or hours of meticulous trial and error. ( the factory did that when these machines were built, but everybody knows better than the factory)