Vacuum Fuel valve repair by Previous Owner.....NOT!

I don't know how I've missed this bodge job before now, except for the fact I hadn't stripped the Petcock before, but I've had a right shock in the last 48 hours.

2 days ago, on the way home, I filled the tank right up, and rode less than a mile home. Yesterday I didn't use the bike, but when I was walking to the shop and as I passed the bike, I got a faint whiff of petrol, but thought nothing of it, as I had filled the tank up and thought that may be why.

Today being a glorius day, I went to go out on the bike, but when I tried starting it on choke..... NOTHING motor spun but didn't even attempt to start, so I assumed that choke wasn't needed, I killed the choke, and opened the throttle and tried to start it again, and again and again (you get the picture). By now, I thought that maybe the battery was getting flat, so went in had a cup of tea, grabbed the screw driver to take the battery off to charge it.

I'd already took the seat off ready, but decided to give it one more try, to start it....... BINGO it started first press of the button, but seemed a little slugish, so I blipped the throttle a couple of times, as I blipped it for the third time, I heard a very loud gurgle and whoosh from the air box, I looked down and saw fuel in the airbox heading up towards me. I hit the kill switch and turned the ignition off.

the next thing I knew I'd got wet trousers and boots - nope not me, but petrol. I got changed, went back to the bike, which was now surrounded by a pool of petrol...... I moved the bike to a dry part of the yard. I knew what had happened immediately, but still took the oil filler cap off to sniff for petrol in the oil, and all I can say is, it would have been harder to sniff for oil, it reeked of petrol.

So I knew I had 2 problems to sort out..... sticking float(s) and a faulty fuel valve. I then checked to see just how much fuel I'd got left in the tank, expecting to have loads......... When in actual fact, I must have had less than a litre. There was that much fuel in the tank that I took the tank off the bike, took the fuel valve off, and didn't lose a drop out of the tank.

I then started to strip down the petcock and what did I find.... I took the 2 small screws out of the faceplate, removed the spiggot and faceplate, thinking that the wave washer was between the 2, BUT it wasn't....

Noooo Way, it wasn't. How it came apart was faceplate - spiggot - below the spiggot and on top of the valve body seal (smiley face), was the wave washer.... No wonder the thing was leaking.

So, now I'm going to follow fitz's "Rebuilding the Yamaha Vacuum Fuel Valve w/pics" and then get to work on the carbs, before emptying the fuel/oil out of the engine and fitting yet another new filter. and filling it with nice fresh oil.

I'll change the oil and filter again after a couple of hundred miles.

Before anybody asks, nope I never came across any fuel or oil on the floor or around the bike previous to this happening. I never smelt fuel in the oil at all previously either. It just happened out the blue, so to speak (even though I know it didn't).

 

Sooo... the wave washer was pushing the seal away from the body of the petcock?

Classic. Just classic.

When rebuilding: If your bike has the "large body" petcock, it may be necessary to "tweak" the metal washer on the backside of the diaphragm in relation to the valve "nub" that has the o-ring on it and does the work. Manufacturing inconsistencies on the aftermarket parts (the only parts available) sometimes lead to that washer not sitting at exactly 90 degrees to the valve plunger so that when the plunger goes into the seat, it won't sit squarely. If that's the case it takes some GENTLE "adjusting" so that it sits square.

I'm beginning to realize that this is more common than not, and should add some of this to my article.

If the 700 has the "small body" style petcock, then never mind.

 

Smurf, you need to go ahead and drain the oil/fuel from the cranckcase, it will ruin the clutch plates if left in very long.

 

No Fitz, the wave washer was pushing the spigot away from the seal, instead of the spigot being pushed towards the seal, which it would be if the wave washer was in the correct place, between the spigot and faceplate. I took the faceplate off, then the spigot and between (underneath) the spigot and the seal, was the wave washer.

Now, you've got me completely lost on that one fitz, I'm assuming that mine is the "large body" petcock, as it's off the 700-X, and the only part that can be unscrewed is the diaphragm cover, and not the output flange. You mention "the metal washer on the backside of the diaphragm" ,do you mean the metal plate on the back of the diaphragm itself, where the spring butts up to (second pitcture down fromt he picture of the repair kits in your article), that might need "tweeking" as there was no washer between the spring and body itself.

 

I am going to, my only problem is I've had to order the oil filter body to engine O-Ring and it hasn't arrived yet.

I can driain the oil out of the engine, and remove the oil filter, and then refill the engine with clean oil, but can't put a new oil filter on until the O-Ring arrives, which might not be until next week. Will the bike be alright sitting there with fresh oil in it, but without the filter and filter housing fitted? The bike is sat out in the open, but with a bike cover on it

Advice please