Gen1 airbox mod?

[Motopsycho87]

Or is there anyone in the UK that can do the boots well?

[Falcon 269]

You need a Dremel type tool with sandpaper roll and then a spearhead stone bit to do the intake stubs:

http://www.yamahafz1oa.com/forum/showthr...+boot+mods

No need to get them absolutely identical.  The aim is to remove the lip between stub and cylinder head and to get rid of the hump in the floor of the stubs. 

If the previous owner refitted standard needles and main jets to carbs which have had the pilot circuit bypass holes drilled, no wonder the fuelling is completely wrong.

[Motopsycho87]

Will get started on them this morning, I've read about how much difference they make and felt the power drop when I put some new stock ones on, I had a feel and the lip is huge!!! What a fail on manufacturing!

Do you know if you can choose not to clip the springs, but still enlarge the event holes on the slides? The supplied guide makes out as if the holes are recommended and the spring is optional, but loses some low rpm response?

[Falcon 269]

I drill out the throttle slides and cut only 1cm off the springs, a compromise that seems to work.  I've done it both ways and to be honest, you'd struggle to feel any difference. 

[Motopsycho87]

Fair enough, so I won't miss out if I leave it you think? I'm trying to see how allowing the pressure to equalise above the slide allows it to open quicker, bearing in mind it's atmospheric pressure above... Can't get my head around it!

Where as altering the spring obviously allows the slide to sit higher for the same throttle position...?

[JKay]

He is the man ,just do wot de man sez  :lol

I can't do anything falcon did mine  :b

[PieEater]

If you want the best results straight off then I wouldn't question the development and testing that went into the Ivan's kit or the experience that Mike (Falcon 269) has in fitting them.

If you're happy to keep taking the carbs on and off so you can prove to yourself the benefits of each modification as a learning experience then fair enough.

[Motopsycho87]

Fine.... Went with falcons recommendation of 10mm... Because metric...

[Motopsycho87]

Can't believe how bad the boots are once you feel the lips where they connect to the head, no wonder you get 5hp just from that!

I'd love to know how you do this in 2.5 hours, I'm a qualified mechanic and a toolroom manager/mechanical engineer, and this is taking me bloody ages! Would love to see you at work!

[Motopsycho87]

All done, been out for a hoon and its lovely! Hunting a tiny bit on idle at 5 turns out on the screws, but who cares :p!!

[Falcon 269]

It's not atmospheric pressure above the diaphragm, that's the thing,

Trimming the spring allows the slide to rise a little quicker but it will still settle wherever the air pressure above the diaphragm determines it should be,

[Motopsycho87]

How can it not be? If vents go to open air surely?

[Falcon 269]

Vents maintain atmospheric pressure in the float chambers.  There's no vent in the carb tops.

[Motopsycho87]

"Vacuum chamber air vent hose" ??? Sorry if I'm coming across as a knob!

[Falcon 269]

Those vents are below the diaphragm.  Above the diaphragm is sealed from atmospheric air so that when the air pressure in the intake throat changes as the throttle plate is opened, the drop in air pressure (transferred via the holes in the throttle slide) causes the diaphragm to 'suck' the slide upwards.

As for doing the Full Monty installation in good time, put it down to practice.  Lots of it.