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Po51uhd View Drop Down
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    Posted: 13 Apr 2018 at 15:53
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote cyclobutch Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2018 at 17:24
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. 
Butch
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GC888 Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2018 at 17:55
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2018 at 19:18
I made a temporary breather box from a jam jar, putting all the pipes through the lid. Worked OK.
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote GC888 Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2018 at 19:23
Originally posted by Brian UK Brian UK wrote:

I made a temporary breather box from a jam jar, putting all the pipes through the lid. Worked OK.

Have you bought a torque wrench yet? Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2018 at 19:44
Originally posted by cyclobutch cyclobutch wrote:

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. 

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.




"Chicken nuggets don't dance on a Tuesday."
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GC888 Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2018 at 19:48
Originally posted by Mike H Mike H wrote:


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.


interesting more food for the Y section and a bigger filter..
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2018 at 20:50
Originally posted by GC888 GC888 wrote:

Originally posted by Brian UK Brian UK wrote:

I made a temporary breather box from a jam jar, putting all the pipes through the lid. Worked OK.


Have you bought a torque wrench yet? Smile

I've owned a torque wrench for more years than I can remember.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2018 at 20:53
Originally posted by Mike H Mike H wrote:

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.

Certainly the air boxes fitted to the new range do incorporate a large volume for this reason. This also applies to the CARC models.
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Motty Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2018 at 23:11
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

It’s more fun to try to ride a slow bike fast .....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GC888 Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 07:44
Originally posted by cyclobutch cyclobutch wrote:

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. 

There are foam pods available that are lighter and obviously more squishy to fit in the space?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote c13pep Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 10:11

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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 15:27
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.
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote GC888 Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 17:39
Originally posted by Brian UK Brian UK wrote:

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.

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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2018 at 19:28
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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