What's This Hose

[Yamahammer1200]

The foil cloth wrapped vacuum line comes off one of the carbs at the intake boot and snakes across the top of the oil cooler before disappearing into the fairing.
What does it do?

[Pat Conlon]

On your '89, it's the vacuum advance hose. It goes to a module under your fairing.
On the later FJ's with the DCI ignition, the advance module is separate from the ignition box. On the early FJ's with the TCI ignition, the advance is built in to the ignition box.
You can read about it here: http://www.fjowners.com/index.php?topic=11690.0

Hope this helps.

Pat

[FJmonkey]

Yep, what Pat said... It is more for emissions than required for proper operation. It don't help and it don't hurt...

[aviationfred]

That is the hose that goes to the infamous Boost sensor located directly beneath the headlight adjuster knob.


Fred

[Pat Conlon]

 "Boost Sensor" ...stop it Fred That was funny.

While you have your tank off, might as well and check the vacuum advance module. Sometimes the diaphragm in those will crack from old age. If this happens, it is not good. It lets in unmetered air into the intake and can cause that cylinder to run lean.

Pull the hose off the intake port and do a suck test.

If you can suck air thru the hose, that's bad: 1) Get a new module, or 2) Cap off at the intake port.

If you can not suck air thru the hose, that's good. Reconnect the hose and leave things alone.

As Mark says, "It don't help and it don't hurt"......but that (throttle closed) flash advance helps keep your plugs clean....and white!

[aviationfred]

"Boost Sensor" ...stop it Fred That was funny.

Pat,

I was being serious.

Look at this add..... http://www.ebay.com/itm/1989-YAMAHA-FJ1200-boost-sensor-/331202743398?hash=item4d1d38cc66:g:KP0AAMXQDnpTaRVD&vxp=mtr


The Vmax uses the same sensor....http://www.ebay.com/itm/Yamaha-XVZ12-83-85-XVZ13-86-89-VMX12-85-07-boost-sensor-pressure-sensor-/321120893504?hash=item4ac44bfa40:g:~GQAAOxyZqhRhqyu&vxp=mtr


Number 24 in the drawing. http://www.partzilla.com/parts/search/Yamaha/Motorcycle/1989/FJ1200W/ELECTRICAL+2/parts.html


Fred

[Pat Conlon]

Yes I know, a rather silly name, huh...

I recall a post last year, or so, from one of our turbo guys asking about this.

[Yamahammer1200]

The module tests O.K.
Thanks for the information, I appreciate it.