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Can I use RTV instead of a gasket?

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Hi, I am rebuilding my 1997 CR125R and there is a gasket that sits between the case halves.  The gasket needs to be replaced because it broke when I disassembled it.  Could I instead use silicone sealant instead of purchasing a new gasket?  If so which kind should I use?  I know there is yamabond and RTV so obviously it can be done, but is it fine for two strokes and my bike in particular?  Thanks!

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The only time I've used rtv is for a quick fix when I had to pull my cylinder to check something and I ripped the gasket so I patched it real quail with rtv but no buy a gasket they are just a few dollars

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As others have mentionned, if it originaly came with a gasket use one as well during re-assembly.

 

But if ever you need to seal up surfaces like reed blocks or say a set of cases that do specify sealant instead of a gasket,

keep in mind that regular RTV usualy isn't very resistant to gasoline. Yamabond or Permatex Threebond type sealers are to be used in such situations.

Edited by mlatour

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I remember my friend used a type of glue/paste on bikes that didn't have gaskets stock.  If there is a gasket.........use it.  The glue/paste is major pain when it comes to rebuilding the bottom end and you have to plain the cases to remove all glue/paste and make surface flat. Gaskets also allow for slightly uneven surfaces to mate w/o leaks.

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The few thousandths that the gasket is may make a difference in how things go together in the final fit.

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RTV may be a temp OK for the right side or left side covers.  They come off easily.  

BUT ! !  if you use RTV in the middle of the two engine halves.....and it begins to leak.....OH Man you have got a lot of work on your hands to re-do it.  

Not worth the chance, use the appropriate gasket.  its worth the wait to do it correctly.  

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The few thousandths that the gasket is may make a difference in how things go together in the final fit.

 

^^^THIS^^^^

 

The dimensional tolerances on the 2 transmission shafts and their spacers depend on the thickness of the gasket material to keep the clearances in check... If you tried to use yamabond to seal the case halves instead of the "PROPER" gasket, you will create a binding of the transmission shafts up against the bearings.. 

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Nice call

 

^^^THIS^^^^

 

The dimensional tolerances on the 2 transmission shafts and their spacers depend on the thickness of the gasket material to keep the clearances in check... If you tried to use yamabond to seal the case halves instead of the "PROPER" gasket, you will create a binding of the transmission shafts up against the bearings.. 

Nice call

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