Black box conversion to open element K+N air cleaner

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jamesp

jamesp

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Hi, I am considering changing out the black box air cleaner on my MKIIa to a K+N air filter. Besides bigger jets, what parts would I need? Thank you.
 
jamesp said:
Besides bigger jets, what parts would I need?
Click to expand...



You'd need an ignition switch bracket and LH side panel upper mount (pin).

...And a longer oil tank breather pipe with a vented catch bottle unless the pipe is left open to atmosphere.
 
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Does the black box offer more restriction than the average K&N pod set?
Ive seen the claim that it does, but area of the stock filter is quite large.
There doesn't appear to be much restriction there.
Has anyone done before and after dyno testing for this modification?
My guess is that to 6500 rpm with an otherwise stock engine there isn't a whole lot in it.
On the other hand, if I'm wrong, free horsepower is always good!



Glen
 
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Before buying the K&N filter I recommend taking the airbox out and seeing if you'll like the look and deciding how you'll handle the ignition switch and side panel. Mine was done that way by the PO and I don't like it.
 
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L.A.B. said:
You'd need an ignition switch bracket and LH side panel upper mount (pin).

...And a longer oil tank breather pipe with a vented catch bottle unless the pipe is left open to atmosphere.
Click to expand...
ok, thank you.
 
worntorn said:
Does the black box offer more restriction than the average K&N pod set?
Ive seen the claim that it does, but area of the stock filter is quite large.
There doesn't appear to be much restriction there.
Has anyone done before and after dyno testing for this modification?
My guess is that to 6500 rpm with an otherwise stock engine there isn't a whole lot in it.
On the other hand, if I'm wrong, free horsepower is always good!



Glen
Click to expand...
I think it does have more restriction. The MKIIa comes with a 230 main jet, the others use a 260 main jet. I have tried using the 260, but it ran rich. Also, the MKIIa had the black cap mufflers, which I don't, but I read in another post that the black caps were not restrictive.
 
marshg246 said:
Before buying the K&N filter I recommend taking the airbox out and seeing if you'll like the look and deciding how you'll handle the ignition switch and side panel. Mine was done that way by the PO and I don't like it.
Click to expand...
I can see your point. The black box does give it a different look and keeps it more original.
 
jamesp said:
I think it does have more restriction. The MKIIa comes with a 230 main jet, the others use a 260 main jet. I have tried using the 260, but it ran rich. Also, the MKIIa had the black cap mufflers, which I don't, but I read in another post that the black caps were not restrictive.
Click to expand...
Another reason I would like to go to the K+N is that it would be easier to remove so that I could adjust the slides.
 
I have a '70 commando with dual 30 mm amals (sleeved so then carbs are well fitting) I have a K&N washable filter and dunstall decibel pipes and I still use the stock carburator settings. I would bet you wouldn't need to change your settings either, expecially if you only change the flow characteristics on the intake only. If you changed to a more free flowing exhaust too, then maybe you might need to make an adjustment to the carb, but that hasn't been my experience, and I have tried larger main jets and different needle positions. Norton got the specifications of the carb settings right. I would always try the stock setting first. In my own case, I falsely beleived that I could run a bigger main jet, add a little more advance and get more top end power. What I got was a bike that stopped accellerating at 85mph, until I went back to the stock main jet size...

The K&N is easily removable with the early oil tank on my bike and certainly allows me to troubleshoot fuel delivery problems more easily. The last time I had one, it was a cracked intake manifold that was sucking air a few years ago. I haven't had to do anything to the carbs besides that for a few years.
 
jamesp said:
Another reason I would like to go to the K+N is that it would be easier to remove so that I could adjust the slides.
Click to expand...
Mine is very easy to remove - extremely hard to re-install. The rubber is hard (probably wasn't originally) and the PO trimmed the rubber shorter. Once I get the rubber over both carbs, I have to tighten the clamps with one hand while holding the filter with the other - need another hand.

I noticed recently that they've lowered the price a lot so maybe I'll try a new one.
 
I have kept my Black Box but changed the silencers from Black cap to peashooters, I run 260 mains and with 230's it just will not pull, 260 is what worked best. What is worth changing is removing the snorkels, never seen them fitted but if they were they would restrict air flow into the black box.
 
Same here with a MK111, open peashooters, stock air box ( snorkels removed) and 260 mainjets.
Pulls to 6400 rpm with a 21 tooth which if I remember correctly is about 115mph.

I believe those original black caps were very quiet and stifling. Perhaps day I'll find an old set and try them on there just to see the result.

Glen
 
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kommando said:
I have kept my Black Box but changed the silencers from Black cap to peashooters, I run 260 mains and with 230's it just will not pull, 260 is what worked best. What is worth changing is removing the snorkels, never seen them fitted but if they were they would restrict air flow into the black box.
Click to expand...
Yes, my snorkels are removed and I am currently running a 240 main jet. The 230s were pretty lean. I bought an extra filter cover plate for the black box and will cut it open below where the filter lays to get more air in below it.
 
What part is the snorkle?

Black box conversion to open element K+N air cleaner
 
o0norton0o said:
I have a '70 commando with dual 30 mm amals (sleeved so then carbs are well fitting) I have a K&N washable filter and dunstall decibel pipes and I still use the stock carburator settings. I would bet you wouldn't need to change your settings either, expecially if you only change the flow characteristics on the intake only. If you changed to a more free flowing exhaust too, then maybe you might need to make an adjustment to the carb, but that hasn't been my experience, and I have tried larger main jets and different needle positions. Norton got the specifications of the carb settings right. I would always try the stock setting first. In my own case, I falsely beleived that I could run a bigger main jet, add a little more advance and get more top end power. What I got was a bike that stopped accellerating at 85mph, until I went back to the stock main jet size...

The K&N is easily removable with the early oil tank on my bike and certainly allows me to troubleshoot fuel delivery problems more easily. The last time I had one, it was a cracked intake manifold that was sucking air a few years ago. I haven't had to do anything to the carbs besides that for a few years.
Click to expand...
Hi, my slides are sleeved, also. I am also running pea shooters, so good exhaust flow.
 
There are a few versions of the pea shooter.
Some , with small exit holes, are quite restrictive.

Glen
 
p400 said:
What part is the snorkle?
Click to expand...

The parts that look like snorkels but they are part of the air box body, there was some insert in the inlet of the snorkel from new ?

I see no reason to wreck the air box by cutting those off, the plastic box was a step in the right direction (Even if true it was a noise control at introduction) as far as a still air box and if need be could be modified in a more humane way for increased flow if that was shown to be an improvement.
It could have the bottom section or rear portion modified/opened below the filter element.

Black box conversion to open element K+N air cleaner



What about the Mk2a east/west battery tray and the 'ham can ?
 
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