Cylinder head vent plug

FSTZ1

Well-Known Member
A couple of days ago it was finally warm enough here in Cleveland to allow me to fire up my '03 bike for the first time this year. I keep it in my garage so it got pretty cold this past winter. After I got back from a short ride, I parked it on the sidestand and noticed oil leaking out of the cylinder head on the left side. I saw that there was a small hole about 1/8 inch in diameter where the oil was coming from. I looked around on the garage floor and found the plug that goes into that hole. It appears to be a vent as the plug has a spring loaded valve in the center of it to allow outside air to be sucked in. I assume the plug just fell out over the winter, or perhaps it was shot out on the initial startup. But it wasn't far from where it was parked all winter, so I believe it just fell out. I used a punch to get it back in, because it wouldn't go back in with just hand pressure. Now I'm wondering if it will stay in there during a really spirited run or if I should go to the dealers and get a new one?
 
give some pictures as to where this plug is.... I'm not sure about which one you're talking about... there is a weep hole that I'm thinking of... but I'm hoping that's not what you're talking about.
 
This picture is from Pat's page but it accurately represents the location of the plug on my bike (gen 1). The vent plug is between the two bolts holding the cylinder head on, and roughly parallel with the bottom of the carb. It's that little round dot between the two head bolts.
 
It turns out that the oil that was coming out of that vent hole on my bike was actually some of the oil I had squirted into the spark plug hole prior to putting it up for the winter. I have since stopped doing that as the lay-up time is not really long enough to cause the pistons to rust into the cylinders. And as far as the vent hole goes, that hole is supposed to be open. There is no plug that is supposed to go into it. It was just a strange coincidence that I found what "appeared" to be a plug laying on the garage floor right under the engine, it had nothing to do with my bike.
 
Hmmmm.... thats interesting the 'coincidence thing' I think perhaps that coincidence was to visit me as well. The bike had been setting for some time and with kids around playing doing heaven knows what in fun, it may have got something squirted into it ....or who knows what....I leaning and hoping coincidence. It did stop today, as today and yesterday were the first time it had been running for a considerable time, 2-3 months.
 
Well, it now appears that it was filled with dirt, ahhh....... a mud dauber home. And the resultant BBQ cooking the larve into crispy critters, thuss leaving those tasty juices running down the cylinder. I'm sure it'll clean up with some WD and elbo grease.
 
Well reading 'Pats' page, it turns out that the said hole is in line with the bosses that the spark plugs screw into, and is the lowest point. That lowest point runs from the far right plug boss along to the left plug boss, continues through the cylinder where you see it on the side of the engine. It's purpose is for a drain, should water get past the spark plug boots. With all the spark plug holes connected by this passagway, all the water that hapens to leak in will then be evacuated out the hole as the bike is leaned over when the kick stand is down and the bike parked........I knew that....no really I was just testing all you guys, no really......................
 
Well reading 'Pats' page, it turns out that the said hole is in line with the bosses that the spark plugs screw into, and is the lowest point. That lowest point runs from the far right plug boss along to the left plug boss, continues through the cylinder where you see it on the side of the engine. It's purpose is for a drain, should water get past the spark plug boots. With all the spark plug holes connected by this passagway, all the water that hapens to leak in will then be evacuated out the hole as the bike is leaned over when the kick stand is down and the bike parked........I knew that....no really I was just testing all you guys, no really......................
05 fz1 on my bike if you look in that hole with bright flashlight you can see where it stops and there is some kind of round copper thing with little lines on top and bottom on the entire thing and then I see in the middle of it numbers first a 9 then space and a 4 . Does anyone know what that is and can you explain it to me please very curious I have never seen this on any one of my other bikes
 

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The only thing in there should be a spark plug and crush washer. You could probably pull the plug cap and look down in there with a mirror.
I'm glad you brought it up though. I just went and looked at mine and it was clogged up tight.
 
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