Looked under the tank today and........

[TaxiDriver]

BUGGER ALL.....



Has this filter,not sure which one it is !!

[Wicky]

All looks bog standard & clean & tidy inc. the filter

If you haven't already got some look at getting some JIS screwdrivers for the crosshead airbox screws.

[fabiostar]

at least it clean and tidy. looks like a hiflo type filter

[podman]

At least your carb filters hadnt turned to a powder...

[VTRDark]

at least it clean and tidy. looks like a hiflo type filter

Don't confuse this with a higher airflowing filter hiflo is a brand of standard filter.

[skye2skye]

Hi looking at the first picture theres a what looks like a tube front and back of air box with what looks like foam inserts what are these for and do the (foam) inserts need to be there

[MacV2]

Hi looking at the first picture theres a what looks like a tube front and back of air box with what looks like foam inserts what are these for and do the (foam) inserts need to be there

According to Honda yes they do or they wouldn't have put them there... They are sub fillters from the cam covers, fillter out the oily air from the cam boxes.

[8541Hawk]

Actually they are the sub-filters for the carb slides.
They allow air to be pulled inot the back side of the diaphragm.

Without them it is the same as running the engine with no air filter, except the dirt gets a free trip trough the carbs first instead of just through the throat.
This can cause damage that can't not be repaired except by replacing the carbs.

So yes they are important

[MacV2]

Actually they are the sub-filters for the carb slides.
They allow air to be pulled inot the back side of the diaphragm.

Without them it is the same as running the engine with no air filter, except the dirt gets a free trip trough the carbs first instead of just through the throat.
This can cause damage that can't not be repaired except by replacing the carbs.

So yes they are important

I slouch correct Sir...

[tony.mon]

Sorry to disagree, Hawk, but I think that the air that flows into the carbs from the triangular filter can only reach the upper side of the diaphragm, so can't get into the engine.
It can only fill the slide and possibly make the spring bind.

Any grit or dust cannot get to the slide unless the diaphragm is split, so there's no additional wear to the carb, the air flowing in through the triangular filters is just to prevent the air that would otherwise be trapped above the diaphragm to have a fixed volume and act as a spring which would affect the carb slide movement.

I removed mine and cut out the corners of the airbox, sealing them to the outer surface and increasing airbox volume. I then fitted some airbox filter foam over the stubs and secured with small jubilee clips so that the air was still filtered.
Having said that, it didn't have huge effects.

[Cadbury64]

I agree with Tony, the sub filters clean up the air reaching the underside of the diaphragm. The top side of the diaphragm is then connected directly to the inlet manifold so the vacuum signal can lift the slides, but there is no direct path from one side of the diaphragm to the other (unless it is buggered).

[8541Hawk]

Well lets look at the carb for a sec.

In order for the slide to lift you need a pressure differential.

So if the cap side of the diaphragm is at atms pressure, how does it lift?
That side of the diaphragm must be at a lower pressure for the slide to lift.


Correct me if I am wrong but don't the "lift holes" lead directly to the cap side of the slide?
How else do you get vacuum to lift the slide if there is no connection?

So even though it is a bit counter intuitive there is a direct path through the carb.

So with no filters the dirty air enters the carb at the diaphragm and is then sucked through the lift holes directly into the carbs.
The first thing normally seen is a build up of crud on the slides and with accelerated wear on the ears that go into the carb body.
Lucky the slides are much softer than the carb bodies but the real issue is the needle jet which can not be replaced on these carbs.

[tony.mon]

You're right!
I didn't consider the vacuum circuit.

But then how does the grit get to the slide ears?

[8541Hawk]

As stuff blows in through the lift holes it hits the slide and needle which are wet from fuel.
So some of it sticks and then slowly builds up.

The grooves that the slide runs in seem to collect the debris the fastest.

[firestorm_al]

The air filter reminds me of Joy Division for some reason