I've got a bike that just had the bottom end rebuilt. Had everything to reassemble it, except, the o ring located ahead of the crankshaft had a tear in it. Looks like it's a water pump channel. I've heard people say you can krazy glue a torn o ring and it will work fine. I'm not sure however. Anyone ever hear of this before? I'm hoping there's something I can do to avoid a 4 day wait on parts for the sake of a 3 dollar o ring.
Can you fix a torn o ring with krazy glue?
- Thread starter Cannon00
- Start date
- Aug 29, 2004
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_JOE_ said:
FWIW, i bought a custom sized o ring from Napa and watched him make it, he cut it to length and krazy glued the ends together. I couldnt believe it, he told me its common practice. I still cant believe it though
Hard to believe, not impossible. Krazy glue almost NEVER works for anything I want it to, it dries very hard and brittle, o rings are soft and flexible? If it does not work, tell us! Around me, napa is no better than auto zone.
where I used to work they had an O-ring kit that you could cut and splice together with crazy glue if a suitable replacement could not be found.....obviously buying a correct one would be better but....
as for the the sealing and staying together I was told the the crazy glue was only to hold it together nicely until you install it after that the channel/groove or whatever it sets in squeezes it to stay together and seal.But you need a clean cut from like a razor blade on the end the more ragged the end the more likely you will have a leak from the edges
Mack truck valve covers have a channel cut into them where you lay a rubber strip in them and only overlap the ends
as for the the sealing and staying together I was told the the crazy glue was only to hold it together nicely until you install it after that the channel/groove or whatever it sets in squeezes it to stay together and seal.But you need a clean cut from like a razor blade on the end the more ragged the end the more likely you will have a leak from the edges
Mack truck valve covers have a channel cut into them where you lay a rubber strip in them and only overlap the ends
2strokerfun
Member
- May 19, 2006
- 1,500
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I tried this on a carb bowl gasket on advise of a mechanic. Next time I took the bowl off, it came apart right where it was glued. Bike ran while it was in there, but I don't know if the glue was holding it together or not. I don't think I'd trust it where there was any pressure involved.
Making custom o-rings is common practice in marine diesel applications. The glue we used was a cyan-type, however, there were other glues that worked as well. The o-rings were used in low pressure, lube, coolant, diesel fuel environments. We never tried to make them for HP steam, any refrigerants, or hydraulics. In these cases the o-rings were usually made from some other compound like silicon, rather than nitrile or butyl rubber. If I was maintaining a dirtbike I would always go with a new ring of the exact size. Remember there are metric, as well as SAE o-rings. The kits they sell at NAPA almost never seem to be the exact size.
- Thread starter
- #10
This is the long version of what I settled on in the end and why:
I read up on o ring splicing and talked to some friends, and apparently it's common engineering practice to use a glue similar to superglue to splice o rings.
Permatex actually makes a specific o ring glue you can buy and lots of places sell lengths of straight rubber to make your own o rings. Since the o ring did have some use on it, and the cost of the glue and rubber to make a new o ring is more than the cost of an actual o ring, I decided not to join a new piece in.
I went to Canadian tire's plumbing section afterwards, and there happened to be an o ring the exact same diameter in thickness, and just slightly(i.e. 1-2 mm) too short to fit. Of course once you tighten the cases together the rubber expands somewhat anyway, so I laid the o ring in the recession and placed a wooden block on it for about a minute. Removed the block and it had taken exactly the same shape as the old o ring minus wear on the old one of course.
In general you shouldn't stretch an o ring, but if you stretch it less than it will expand where it's seated it will be fine(advice from a mechanical engineer friend).
Another reason not to use the superglue in this position is that I don't know how well it stands up to solvents like gas, and since it's a water pump I didn't know if the heat would exceed the 130 degrees celsius the super glue is rated to withstand.
I did however test a tube of *new* superglue on a spare o ring. Once cut and joined with the glue it was almost impossible to break the join. Typically pulling on it, it would tear just slightly after the join, indicating that the superglue was plenty strong, but the rigidity of it caused the nearby rubber to absorb more strain in situations where tension is placed on the o ring. To the guy who had an o ring fall apart in the carb, I suspect gasoline destroyed the glue, the permatex o ring glue may be unaffected by solvents, but I didn't look too far into it.
I read up on o ring splicing and talked to some friends, and apparently it's common engineering practice to use a glue similar to superglue to splice o rings.
Permatex actually makes a specific o ring glue you can buy and lots of places sell lengths of straight rubber to make your own o rings. Since the o ring did have some use on it, and the cost of the glue and rubber to make a new o ring is more than the cost of an actual o ring, I decided not to join a new piece in.
I went to Canadian tire's plumbing section afterwards, and there happened to be an o ring the exact same diameter in thickness, and just slightly(i.e. 1-2 mm) too short to fit. Of course once you tighten the cases together the rubber expands somewhat anyway, so I laid the o ring in the recession and placed a wooden block on it for about a minute. Removed the block and it had taken exactly the same shape as the old o ring minus wear on the old one of course.
In general you shouldn't stretch an o ring, but if you stretch it less than it will expand where it's seated it will be fine(advice from a mechanical engineer friend).
Another reason not to use the superglue in this position is that I don't know how well it stands up to solvents like gas, and since it's a water pump I didn't know if the heat would exceed the 130 degrees celsius the super glue is rated to withstand.
I did however test a tube of *new* superglue on a spare o ring. Once cut and joined with the glue it was almost impossible to break the join. Typically pulling on it, it would tear just slightly after the join, indicating that the superglue was plenty strong, but the rigidity of it caused the nearby rubber to absorb more strain in situations where tension is placed on the o ring. To the guy who had an o ring fall apart in the carb, I suspect gasoline destroyed the glue, the permatex o ring glue may be unaffected by solvents, but I didn't look too far into it.
