1991 ST1100 Valve Cover Gasket Replacement

TwoDogs

TwoDogs

Joined
Aug 26, 2018
Messages
6
Location
Mooresville Indiana
Hello, I hope everyone is well.
I have a right side valve cover gasket that is seeping a little oil. I have ordered the gaskets and was just wondering if you all had any tips on replacing the gaskets or how hard of a job it may be? I ordered two because if one has started to leak the other side is probably not far behind. The ST I have sat for seventeen years before I purchased it so I can see why the gaskets would start to let a little oil pass and I have only put two thousand miles on it since I put it back on the road late last summer. Thank you all in advance for any knowledge you can pas along.
 
I'd also replace the 4 (8) seals under the cover bolts...
After cleaning all carefully I apply a very faint layer of glue (Pattex) into the groove of the cover (don't forget the spark plug hole) to keep the gasket in place, then a dab of engine sealer where the half round parts meet the plain section, place the cover on, bolts with new seals torqued to spec...
 
In my observations, it is very easy to trap the rubber heat shield at the back of the cover (ie the long side nearest the carbs), when the cover is Finally located and secured. It is easy enough to feel down the back to make sure that the shield is free, but if it gets trapped, it squashes the gasket. The next time the cover comes off and is replaced, the part of the gasket that was squashed too much, does not seal properly.

Both of my gaskets on my 2 second hand bikes had this problem, caused before I bought them.

Check the heat shield isn't trapped before tightening the bolts.
 
+1 on replacing the seals under the bolts as well. When I replaced my cover gaskets, I glued them in a few spots to hold them in the cover, then placed that assembly on the head. I think this made it easier to get everything aligned and not pinch the gaskets. Make sure you put a dab of sealant at the corners of the u-shapes on each end of the gaskets. Careful torquing the cover bolts, they hit a hard stop and can easily be snapped.
 
paulcb said:
+1 on replacing the seals under the bolts as well. When I replaced my cover gaskets, I glued them in a few spots to hold them in the cover, then placed that assembly on the head. I think this made it easier to get everything aligned and not pinch the gaskets. Make sure you put a dab of sealant at the corners of the u-shapes on each end of the gaskets. Careful torquing the cover bolts, they hit a hard stop and can easily be snapped.
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Can you add sealant under the bolt head washers if new seals are not available
 
The new seals provide a bit of compression to the valve cover gasket when they are squeezed as the bolts are tightened. As both the gasket and seals age, they compress and loose elasticity. Sealant will not provide this compression to the gasket, and you should not even think about over torquing the bolts - they will bottom out and snap.

Ron Ayers shows the parts in their exploded diagram - RUBBER, SETTING 90543-MV9-670. But that does not mean the parts are available.
 
its been a few years since I had to replace those things, which I referred to as "grommets", but as I recall they are flat on the top, right? If so, would it be possible to set a metal washer on top of each of them to take up the gap caused by them compressing over time? Much cheaper, and always available. The question would be is there a common washer that has the correct I.D. and O.D. for the application.

edit: after writing this I remembered that in addition to providing clamping force, the grommets also have to provide an oil seal around the bolts as well, so adding a plain metal washer on top may compromise the oil sealing capability, and probably won't work. I think both the bolt shaft and head need to be in close contact with the grommet to provide the oil seal, so raising the bolt head with the washer will probably compromise the oil seal.

But, its easy enough to try it and see what happens.
 
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dwalby said:
I think both the bolt shaft and head need to be in close contact with the grommet to provide the oil seal, so raising the bolt head with the washer will probably compromise the oil seal.
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IMO those items are consumables... like the carb boots are they cheap enough that I don't take any chances and simply replace them every 2~3 years...
 
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