2 questions. 81 special

[Tbell]

There is a vacuum ?? line that is clamped to the top center mounting bolt/clamp for the breather box. Where does it connect?

If the octo valve doesn't seal to shut off the flow of fuel is there any other problem other than having to manually turn off the petcock? There isn't a vacuum associated with normal fuel flow when in the on position is there? Just gravity feed? Thanks!

Tom

[CatatonicBug]

Hard to tell on the vacuum hose, since nothing is "supposed" to be clamped there. There should be a drain line from the battery, and a vent hose from the Middle drive. However, both should hang down behind the engine, pointed at the road.

As for the octy, it stops the fuel flow when the engine is not running. However, so should the float valves in the carbs. If your octy is not sealing, you can rebuild it (I have the octy portion of a rebuild kit if you're interested). Otherwise, you can turn off the petcocks if you like, and hope they are sealing. Once you turn them back on, and the engine is turning, the octy should then allow fuel to flow freely (assuming that the vacuum line is connected to it).

[DGXSER]

There is a vacuum ?? line that is clamped to the top center mounting bolt/clamp for the breather box. Where does it connect?

Sounds like your describing the large line that is the crankcase breather vent. It is about 5/8-3/4" round and connects form that center nipple on the air box to the breather vent at the back right side of the crankcase.

If the octo valve doesn't seal to shut off the flow of fuel is there any other problem other than having to manually turn off the petcock? There isn't a vacuum associated with normal fuel flow when in the on position is there? Just gravity feed? Thanks!

Well, the Octy is a normally closed valve, the spring in there shuts it off. So with no vacuum, or a cracked or leaky vacuum hose or diaphram, the valve will close. Provided the o-ring is still capable of sealing, nothing will go by to the carbs. This how alot of bikes end up being set to Prime to run all the time. So, unless the o-ring leaks badly, it may not give enough fuel to the carbs.

Typically when in the ON position with the Octy installed, the small niple on the side of the octy gets a vacuum line connected to the synch vacuum nipple on the no 2 carb boot close to the head. This pulls the diaphram back on the octy pulling the o-ring form its seal and then gravity will feed the carbs. If you do not remove the Octy, you may want to run in the Prime position and then turn the petcocks to off when not in use.

[prometheus578]

Mine hangs down... hasn't pointed up in years

...and a vent hose from the Middle drive. However, both should hang down behind the engine, pointed at the road.

My vent hose from the middle drive also was hangin' down... but someone wiser years ago said that there's a clip for it somewhere on the air box so that it vents upward.

[Tbell]

My vent hose from the middle drive also was hangin' down... but someone wiser years ago said that there's a clip for it somewhere on the air box so that it vents upward.

That has to be the middle drive vent hose. I sure didn't remember disconnecting it. There is a bracket that it is connected to and the same bracket also acts as a clamp for the wiring harness.

As for the octo, I was confused about the meaning of pri and on. Got them reversed. Thanks for clearing this up for me.

Tom

[natemoen]

prom is right about the hose being the middle drive vent hose. There should be a little nipple right next to the crank case vent and that is where it hooks up.

[XS1100_OEM4ME]

Prim

If you had the gas leak when in "prim", not in "on" your octy my be fine as prim bypasses the octy valve. It would be nice if the float needles never leaked, but they can and that is why yamaha spent the cash for the octy

[DiverRay]

And you do want it UP! One of my '79s had it pointed down, and it sucked water from riding in the rain. Later when I did a "high speed run", the water boiled and pushed all the oil out! Found it because of the tan mud all over the back of the bike.

[XS1100_OEM4ME]

Gas leak

Also, if you had a gas leak through the carb's, check your oil for gas that could have leaked past pistons to crankcase, if so, change it before you run it!

[Tbell]

Also, if you had a gas leak through the carb's, check your oil for gas that could have leaked past pistons to crankcase, if so, change it before you run it!

I am only in testing mode for the octo valve. There was never a time when the fuel was hooked up to the carbs so no problems there. At present I am manually switching to the off position. It is something I'm in the habit of doing with my 76 Wing anyway. Waiting on brake parts now. Can't ride until I get them rebuilt. Everything else is ready to go. Getting antsy. Thanks guys!

Tom

[XS1100_OEM4ME]

octy

That good about no carb overflow. You can test the octy by turning petcocks to "on"check for flow to carb lines, if none, add vac. to octy vac. line (the small one, you can just suck on it acording to clymer man.) if it flows and stops when you remove vac. it is working.