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Old 10-11-2011, 10:55 AM   #1907
dirty_sanchez
Dirty_Sanchez
 
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Joined: May 2006
Location: Louisiana, Baton Rouge
Oddometer: 2,508
Quote:
Originally Posted by bmwktmbill View Post
Dirty,
Last I sealed the top of the engine I used Red hi-temp RTV.

It worked OK, leaked a little.

What are you recommending for that these days?

Also on the road it might be necessary to reuse a base or head gasket if the engine has to come apart and fresh spares aren't available.

Can you recommend anything for reuseing these and if so does the torque spec stay the same?

Should the head be retorqued?
Should the engine top?

bill
Bill-

The automobile industry stopped using cut gaskets like the ones used to help seal the valve inspection covers on the LC4 Mill back in the '70s. And there's a reason for it.....cut gaskets are prone to taking on a compression set which results in leaks.

I try not to use cut gaskets on anything that uses a spark plug in our house and use instead...you might guess, one of which ever Gasket Eliminator product I have closest. 518, 515, or even 510 all would be entirely suitable.

Acetoxy cure RTV's like ALL red high temp RTV's don't play well with non-polar fluids such as oils and fuels. The hydrocarbons absorb into and are attracted to the silicone molecules, then sometimes slowly and sometimes rather quickly the RTV breaks down and a leak is born. This is what you experienced. Then there's the small bit of squeezeout that will become dislodged and might come to rest at an oil pump intake location.

Plus RTV's we all use are cured by moisture. As soon as a thick or thin bead of RTV or any other solvent based gasketing product is applied it immediately begins to cure and skin over. If you fiddle around once you draw out a bead of RTV, by the time you mate the surfaces it's already skinned over to the point the exposed product has cured to the point it won't wet out the mating surface which is needed for a satisfactory seal.

Gasket Eliminators have no open time to worry about like you do with the gasketing products mentioned above. You could apply the material, go to lunch, take a week vacation, then return and mate your parts. It doesn't begin to cure until you remove air from the equation...mate your parts and tighten things up.

A little 6ml tube (think small like a tube of Chapstik) of 518 is an ideal thing to have in a tool bag.

The use of Gasket Eliminator does not change the torque specs.

On the inspection covers I dab a thinnish visable film on the top of the head, place the covers in place, then with a bit of blue threadlocker on the hex head bolts thread them in. Once finer tight, I'll go back around and snug everything up, then wipe off any squeezeout to keep the dust from finding a place to call home. Because we're not using an elastic/mildly compressible gasket, arriving at "tight" feels different. I suspect you work on your own bike so you should know how tight...tight is. I've never torqued these buggers with a real live clicker torque wrench.

A head or base gasket can be removed and reused by dressing both sides of the gasket with a thin film.

Careful work with a razor blade will allow you to remove the head or base gasket. Tedius, but I've done it with no real issues.

Once everything is buttoned up, no need to re-torque simply because you upset the seal. Same goes for nuts and bolts with a threadlocker.

My LC4 does not have any sort of oil leak.

Dirty
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dirty_sanchez screwed with this post 10-11-2011 at 11:01 AM
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