Air filters |
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Po51uhd
Falcone Joined: 28 Oct 2016 Location: Cheshire Status: Offline Points: 36 |
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Posted: 13 Apr 2018 at 15:53 |
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hello
I have a v35 ii and wish to replace the airbox / air filter with simple k&n jobs. Should I use the existing manifolds and buy clamp-on filters (space is very limited) or is there a better solution that bolts directly onto the back of the carbs? Thanks Stephen
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cyclobutch
Senior Member Joined: 08 Sep 2015 Location: Essex Branch Status: Offline Points: 750 |
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You should be able to get pods that bolt onto the back of the carbs directly.
But my advice is don't go there, stick with OE. On the big twins the carbs are solid mount but on the littluns you've got those inlet rubbers - you'll be hanging a load more weight off those that they won't particularly like. Changing the std filter is a bit of a PITA but in the UK you only really need to do this every two or three years. And you can make it easier by switching to a wing nut at the nose of the unit the next time you do the job.
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Butch
V50 II - 'The Black Pearl' T3 - 'Blue' Eldo Loop - 'Jug' |
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GC888
Senior Member Joined: 21 Dec 2015 Location: Manchester UK Status: Offline Points: 174 |
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Will be interested in replies to this as I'm planning the same.
I haven't yet measured or looked into any of the technical side.... But I will have more space to add a K&N directly to the carb, as I have discarded the big battery, toolbox, filter box and rear mud guard! My thoughts/concerns are around 1 - the breather box that the cam boxies link to...The small Le Mans breather box could be a solution though its expensive for what it is. So was going down the line of fabricating my own from a thick walled alloy tube (that have knocking around the garage) that I could drill and tap spigots and brackets on/into with a mini K&N vent. (though some people just let it vent to air/road and top up the oil more regularly!) 2 - if re jetting will be required - not sure on this as the OEM box isn't restrictive its just big and ugly. This may be more of a question if I change the silencers to something more free flowing! 3 - the carbs point 'in' on the original I was considering trying to reverse the inlet so it pointed 'out' to give the filters more space - but this isn't something I have tried or even seriously looked at yet. 4 - fabricating a Y piece to accomodate a single filter to service both carbs. (the cylinders will be on different strokes) Lookforward to replies
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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I made a temporary breather box from a jam jar, putting all the pipes through the lid. Worked OK.
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Brian.
Better 5 minutes late in this world than years early in the next. |
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GC888
Senior Member Joined: 21 Dec 2015 Location: Manchester UK Status: Offline Points: 174 |
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Have you bought a torque wrench yet?
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Mike H
Senior Member Joined: 21 May 2014 Location: East Anglia Status: Offline Points: 8733 |
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Plus, never had a small block but I've read that the stock air filter box is also a still air reservoir which makes the bike perform better than without. (Issues include flat spot in the midrange, apparently.) I also bought into the K&N sales blurb in the past but according to later info on the grapevines seems they can clog up quickly, especially the small ones ("pods"), and can be too small area for wide open throttle and so restrictive (and especially if over-oiled), come to think of it I tried small pods on my 850 Le Mans, but was not overly impressed. The much bigger oval K&N's on the other hand worked and lasted better, but they only fit the big blocks AFAIK. |
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"Chicken nuggets don't dance on a Tuesday."
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GC888
Senior Member Joined: 21 Dec 2015 Location: Manchester UK Status: Offline Points: 174 |
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interesting more food for the Y section and a bigger filter..
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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I've owned a torque wrench for more years than I can remember. |
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Brian.
Better 5 minutes late in this world than years early in the next. |
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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Certainly the air boxes fitted to the new range do incorporate a large volume for this reason. This also applies to the CARC models. |
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Brian.
Better 5 minutes late in this world than years early in the next. |
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Motty
Senior Member Joined: 03 Jun 2015 Location: South England Status: Offline Points: 269 |
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The rear rubber section of the original airbox fell to pieces on my bike (there was a photo on here at the time)
I have fitted individual pod filters, whilst doing so I increased both pilot jets and main jets. Since then I have only done a couple of hundred miles, I still need to fine tune the jetting. I vented the breather tubes to fresh air, if this actually becomes an issue I will sort out a catch bottle for the oil |
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It’s more fun to try to ride a slow bike fast .....
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GC888
Senior Member Joined: 21 Dec 2015 Location: Manchester UK Status: Offline Points: 174 |
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There are foam pods available that are lighter and obviously more squishy to fit in the space?
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c13pep
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There are foam pods available that are lighter and obviously more squishy to fit in the space? [/QUOTE] I fitted foam pods to my V50 for the above reason but also because they were less restrictive in the inlet tract than the stainless mesh type. A point to make is that on my PHBH28 carbs there is a drillway from the intake flange to the `choke` plunger chamber (not sure if V35 are same) which needs to be plugged if pods are fitted directly to carb. (Eurocarb advice) CHRIS |
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you can`t have any fun in a straight line
Monza Honda CB77 project |
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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The shape of the air intake for the carb is important. Look at the original parts, you will see a trumpet shape. Doing away with this by fitting pod type filters can lose some bhp.
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Brian.
Better 5 minutes late in this world than years early in the next. |
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GC888
Senior Member Joined: 21 Dec 2015 Location: Manchester UK Status: Offline Points: 174 |
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Hi Brian Do you have any more information on this as I am trying to understand the engineering behind it. The existing filter is a long folded paper cone filter fills a good size air box. This should give a relatively slow air velocity through the filter without hindering the induction flow. I can see why MG would decide to go this route as the after all the bike is a basic commuter and would be expected to contend with Mediterranean dust day in day out and potentially poor maintenance. I guess the cone shape is to aid airflow...but don't know? Directly replacing the OEM filter with a pod folded paper and mesh (unusually) may restrict the flow more than the OEM as the area of a folded pod is about half the size of the OEM and has no air box. It would reduce the volume of the 'air dam' in the box. Though in theory that would only effect initial acceleration of the engine as the pressure reduced in the air box over a second or so before maximum flow through the filter was attained. This would make the bike run rich - unusual as pods general do the opposite! Therefore there is the potential that running the carbs without filters open to air may be relatively close to putting a new clean filter on...I feel a sudden liking for mesh trumpets.... So if using pods a bigger longer profile will be as closer to original flows than the short stubby ones. (easy to work out the comparative surface areas of original and replacement) Or the reticulated foam pods that provide very little restriction (some of these have an angle inlet) But it would mean trumpets mesh or otherwise are an option. Have people switching to pods gone up down or same on jetting with what results? |
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Mike H
Senior Member Joined: 21 May 2014 Location: East Anglia Status: Offline Points: 8733 |
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Pods can make the engine run rich if they can't pass enough volume of air for large throttle openings. Especially when getting clogged up with dirt. Because of the small surface area that could be a short time.
I saw a graph recently when someone actually tested all these filters for volume of flow, using a special machine for the purpose, I think with dust added also to show drop off of performance with use. IIRC all the pods did poorly in terms of working lifetime. |
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"Chicken nuggets don't dance on a Tuesday."
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