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Hydra

How to repair piston?

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Hi all.

I would like to know if is possible to repair this piston. The central window port is a mistake, and I need to close it. 

How could I save this piston? Welding? Glueing with metal adhesive? Any other idea? Thanks in avance.

pistonitalkitagujeros.jpg

Edited by Hydra
Orthographic

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I Tig welded a hole in the crown of a piston that was made by a valve trying to escape. Apparently the engine ran fine afterwards,but it was a Rover K series. I think if it is measured after the weld and its not distorted it should be fine. Rod choice for the filler metal should be a big consideration.

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Hi, why would you need to close it off ? If there are no ports in the cylinder matching, it won't do any harm.

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43 minutes ago, brownie001 said:

Hi, why would you need to close it off ? If there are no ports in the cylinder matching, it won't do any harm.

This central window must be closed because if drilled, the gas goes back to the carburetor. All depend of the transfer diagram. This piston (with central window) would work on a Bultaco pursang, but not on a sherpa

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If you weld it, measure it very carefully before. multiple diameter readings all round, ring grooves, skirt dia etc.

Pre heat it to help reduce distortion, also make a plug that is a tight fit and weld it in. (less shrinkage/ distortion).

Use TIG and do little bits at a time, allowing the weld to cool to preheat temp, patience is key.

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perhaps making a plug that fits tightly - then drill and pin ?    or drill and screw ?    or glue if you can find something that will withstand high temperatures ?

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2 minutes ago, djr said:

perhaps making a plug that fits tightly - then drill and pin ?    or drill and screw ?    or glue if you can find something that will withstand high temperatures ?

Mmmm. This sounds interesting. But I dont understand "drill and pin" or "drill and screw". I understand the words, but I dont visualize the idea. Could you attach a drawing?  

 

Thanks before hand

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Is it that special / rare that’s it’s worth the gamble of either ruining the piston or damaging the engine if the repair weakens it ? If not, buy a new one and stick that one on eBay 

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17 minutes ago, brian0304 said:

Is it that special / rare that’s it’s worth the gamble of either ruining the piston or damaging the engine if the repair weakens it ? If not, buy a new one and stick that one on eBay 

Yes. You are right. I will not start any try if I am not absolutely sure. In fact, I have  bought a new pistón, but I own several sherpas and, may be, I could test a repair.

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Put it in the bin. Welding will distort it and distroy the heat treatment. The piston skirt is a very complex shape it is tapered,possibly barrel shaped and oval. This compensates for expansion / temperature gradent from to to bottom .

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What about a countersunk rivett?

No heat, no glue. 

Just a pair of thin metal sheets, one outside, embedded in the concave hole, one inside for fixing the rivett.

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