stray vacuum hose... help.. 1990 fj1200

[zoomjay]

Okay, putting the finishing touches on my 1990 fj1200...  I replaced the speedometer cable and when I was putting the fairing back on I found a "stray" vacuum hose under the "vent" on the right side (in attached picture).  I looked and looked although cannot figure out where it goes.  Can any of you tell me what it connects to? 

I have also noticed that my tach is now slow to operate... maybe the two things are related??

Thanks.

[FJmonkey]

We can help if you tell us where the other end of that tube is connected. Sounds like you have a vacuum leak if not running properly.

[Firehawk068]

The vacuum hose has nothing to do with the tachometer.

That vacuum hose should connect to a small little box up under the right side of the fairing. Yamaha calls it a "Boost Sensor"
It is designed to advance the ignition timing when a vacuum is applied. A few of the more knowledgeable folks on here have indicated it is only for emission purposes.
Running the engine with that vacuum hose disconnected will result in a lean air/fuel mixture in whatever cylinder the other end of that hose is plugged into. (usually cylinder #2)

Look way up under the right side of the fairing, attached to the fairing sub-frame the little box should have a small hose nipple on it.

[aviationfred]

The end that is showing in your photo attaches to the 'Boost Sensor'. If you remove your main fairing, it is located in the sub-frame near the headlight adjuster. The nipple on the sensor points down.

Here are a couple of links to help identify and locate the 'boost sensor' and hose.

It is #24 in the diagram http://www.partzilla.com/parts/search/Yamaha/Motorcycle/1989/FJ1200W/ELECTRICAL+2/parts.html

In this diagram the hose that you see could be the #31 hose. If you follow it, you can see that it does attach to the #2 cylinder intake boot. http://www.partzilla.com/parts/search/Yamaha/Motorcycle/1989/FJ1200W/AIR+FILTER+%28NON-CALIFORNIA+MODEL%29/parts.html


Fred

[gumby302ho]

 Man you guys are good, I will thank you even if zoomjay didnt or just forgot!