oil leaking out of strange hole in cylinder head

dwalby

dwalby

Joined
Mar 13, 2012
Messages
4,835
Location
soCal
Bike
'97 ST1100
So today I did a valve check and coolant flush (hey Jim Van, its really boring when you do it at recommended intervals and the coolant looks almost like when you put it in).

Started it up for a leak test, and found one, a really bad one. Never knew what this was so I'm asking for help from the forum.

At the rear of the cylinder head, on both heads, there's a weird cone shaped hole in the back of the head. Oil is oozing from the one on my left head. I'm guessing I'm going to have to replace the head to repair this? Anyone familiar with this leak?

Here's a picture

IMG_2995_opt.jpg
 
Was not this discussed in another thread? Is it the drain that someone was talking about? I forget the specifics and the name of the thread, but if it is what I think, it was designed in to drain away oil leaking farther up. Maybe some part of the valve cover gasket? Sorry I can't be of more help. Replace the whole cylinder head? No. Maybe a new valve cover gasket. Someone else will answer this more knowledgeably.
 
SMSW said:
Was not this discussed in another thread? Is it the drain that someone was talking about? I forget the specifics and the name of the thread, but if it is what I think, it was designed in to drain away oil leaking farther up. Maybe some part of the valve cover gasket? Sorry I can't be of more help. Replace the whole cylinder head? No. Maybe a new valve cover gasket. Someone else will answer this more knowledgeably.
Click to expand...

I think what you're referring to is part of the 1300 engine, this is an 1100.

edit: I went out to look again, and there's no sign of any leakage from the valve cover gasket, which is the only oil leak related item that was changed. It is odd though that something like this would happen right after a service. It doesn't leak much, its just a dribble, but steady enough that if it was a pre-existing condition I probably would have had some noticeable oil residue on the lower fairing panel below the leak. But I haven't put the lower panel back on yet, its possible that it just drips straight to the ground, but I had no oil puddle in the garage either.
 
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Sorry, Doug. You are probably right. A cast hole in both banks of cylinders (regardless of the engine) sounds like a drain, not damage or a defect. I would still bet on something like a valve cover gasket. Where is Larry or Mr. Heath when we need them? Probably out riding if their weather is anything like what we have here right now.
 
So you had the valve covers off Doug. You will recall that the gaskets also run a circle around each spark plug hole. Those spark plug wells connect to those two holes on the rear of the head. My guess is the gasket around one, or both, of those spark plug cavities did not sit correctly when the valve cover was re- installed, thus you have oil blowing out past the gasket and out that rearward hole.

I always put a very thin line of Permatex Blue sealant along the entire gasket, on the valve cover side, to make sure it stays in place while mounting the valve cover.
 
Thanks a ton Bush, you're exactly right. The spark plug boots completely cover the plug hole, so I totally forgot about those circles when searching for leaks. Pulled the plug boots and there's oil in there at the bottom. I used gasgacinch on both gaskets, I guess I didn't do as good a job on the left as on the right.
 
all better now, thanks again Bush !!!

and I learned something new about a bike I've owned for 20 years, go figure.
 
Bush said:
That was a lot easier than replacing a head, wouldn't you say? Glad it was the easy fix.
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yeah, since we're both on the Pacific coast, if I run into you at some STOC event, I'm buying.

I was thinking that might have been some kind of machining port that was sealed off after machining, and somehow the seal failed. Never even thought about the gasket around the spark plug until you mentioned it. Out of sight, out of mind. duh.
 
dwalby said:
Thanks a ton Bush, you're exactly right. The spark plug boots completely cover the plug hole, so I totally forgot about those circles when searching for leaks. Pulled the plug boots and there's oil in there at the bottom. I used gasgacinch on both gaskets, I guess I didn't do as good a job on the left as on the right.
Click to expand...

What is gasgacinch? A sealant like RTV silicone sealant, like Permatex gasket goop, but simply another brand? Glad it was so easy and cheap a fix.

Two years ago, after I refilled the preload cylinder and fiddled with the damping screw on the shock, I experienced handling problems in turbulent air. Someone said if I had problems after only touching one thing, I probably did something wrong to said thing. Sure enough, tightening up the dampener a bit, and adjusting the preload to stock solved my problem.
 
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