Flat to round air filter conversion

[ME 109]

After running a K+N for about 8 years, my airbox has been clean enough, considering the gravel roads I often travel.

Yesterday I decided to 'fix up' my airbox by re-installing the intake extension tubes, and the breather extension tubes that go down into the carby intake. I somehow lost them years ago and have done without them.

I also put a paper filter back in there ('cause I had one)

Also, I'm lending a pair of straight through Staintune mufflers.

A test ride yesterday showed a little better midrange response, which may also have been the result of a crisp autumn air.........

Love those staintunes!

Re the K+N's, I bet there are plenty of dusted /7 engines from the improper fit of the filters and the ignorance of the new K+N buyer of the need to modify the filter.
Stupid ain't it! An expensive filter that fails to do what it is meant to without being modified.
What else would a K+N airhead filter fit besides an airhead?? Why would the manufacturer not correct such a huge *uck-up with their product?

[SteveD]

I would NEVER run a K&N filter on ANYTHING or buy a vehicle that used one, there is a reason that they flow-good, because they do not filter anything other than Children, Dogs and small-rocks.

Vince

It's no exaggeration to say that the undecideds could go one way or another.
George H. W. Bush

[Unclviny]

Having looked into K&N's on a few occasions I have always reached the same conclusion, NOT ON MY VEHICLES!

Vince

[John Falconer]

Back on the topic of the conversion.

Not a big deal - just get the latest parts ('79 or so) if you can. The earlier aluminum pieces only accommodate a single breather tube. You can make the earlier style work but it takes a bit of grinding and filing to provide a path for the right-side breather tube.

BTW - K&N - no, except if in dusty dirt bike, where the cost of replacing paper gets high. The engines don't tend to get the miles of our road bikes either.

[Roy Gavin]

Back to the origonal topic, if I may.

Rob Farmer, from the UKGS Forum rigged up a O2 meter to his 1000 cc bike which he could read while riding the bike.

He found that in the upper reaches of the rev scale the flat filter didn't flow enough, upsetting the mixture.

He changed to a round filter, which had sufficient flow.

Moorespeed racing has a airbox top for the flat set up with a circular filter on top , presumably designed to overcome the flow deficiency.

I have read a few other theories for improving flow, from using the cardboard tube from the centre of a toilet roll as a funnel on the inlet (Snowbum) to adding a spacer to the airbox somewhere (Attributed to HPN).

My own fiddling gives different results on different bikes with different exhaust systems, so I dont think there is any simple answer to the question. And some of the results I get mare the opposite of what other folks achieve.

But if you fit a less restrictive exhaust and manage to tune the inlet system and carburation to suit you will get a crisper and more powerful motor - no engine ever ran its best with a restrictive inlet or exhaust system.

[ME 109]

Back on the topic of the conversion.


BTW - K&N - no, except if in dusty dirt bike, where the cost of replacing paper gets high. The engines don't tend to get the miles of our road bikes either.

Oi! stick to the point!

[Dane]

Hi All,
Thanks for all the responses.
To sum up the conclusions I have drawn so far:
- Flat to round filer is no problem - may require a bit of filing to accommodate breather arrangement. Carb adjustment, jets/needles may not be an issue, at least with an OEM paper filter.
- As foreseen the K&N-option sparked some controversy. On my a bike which, as mine, is ridden only occasionally and not in a very dusty environment it is probably not worth it, even if it may, under some circumstances, give a slight boost in performance. As I am riding a 30 year old machine with - (when it was new) 70 BHP to 225 kg + 0.125 tonne of rider, total performance is not that high up on my list of priorities, so I will stick to OEM paper. (An eliminate a few Urquells from my diet and maybe even hit the gym if performance becomes an issue...)
Once again thanks guys.
Dane

[Bob Distelcamp]

Hello,
One of the reasons I stayed with the flat filter for my R100RS and my R80RT was it is much easier to
run a larger breather tube out of the housing. I did this on my R90S. I had to get a breather cap for a R65
drill hole in starter cover on,on,on
It's just something to also thing about.

Bob Distelcamp

[Major Softie]

It's just something to also thing about.

Bob Distelcamp

Always love thinging about.

[ME 109]

Always love thinging about.

Yeah, we thaw you thinging with your blewth band.