Hydra Posted June 2, 2019 Report Share Posted June 2, 2019 (edited) 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. Edited June 2, 2019 by Hydra Orthographic Quote Link to comment Share on other sites More sharing options...
jimmitchell Posted June 2, 2019 Report Share Posted June 2, 2019 Any heating localised heating ie welding, will not be good for the piston as it will cause distortion. Quote Link to comment Share on other sites More sharing options...
teamferret Posted June 2, 2019 Report Share Posted June 2, 2019 I've used devcon F and it's held up surprisingly well Quote Link to comment Share on other sites More sharing options...
jon v8 Posted June 2, 2019 Report Share Posted June 2, 2019 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. Quote Link to comment Share on other sites More sharing options...
brownie001 Posted June 2, 2019 Report Share Posted June 2, 2019 Hi, why would you need to close it off ? If there are no ports in the cylinder matching, it won't do any harm. Quote Link to comment Share on other sites More sharing options...
Hydra Posted June 2, 2019 Author Report Share Posted June 2, 2019 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 Quote Link to comment Share on other sites More sharing options...
still trying Posted June 5, 2019 Report Share Posted June 5, 2019 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. Quote Link to comment Share on other sites More sharing options...
djr Posted June 5, 2019 Report Share Posted June 5, 2019 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 ? Quote Link to comment Share on other sites More sharing options...
Hydra Posted June 5, 2019 Author Report Share Posted June 5, 2019 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 Quote Link to comment Share on other sites More sharing options...
Hydra Posted June 5, 2019 Author Report Share Posted June 5, 2019 Ok. Now I understand your idea, and It sounds fine! Quote Link to comment Share on other sites More sharing options...
brian0304 Posted June 5, 2019 Report Share Posted June 5, 2019 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 Quote Link to comment Share on other sites More sharing options...
Hydra Posted June 5, 2019 Author Report Share Posted June 5, 2019 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. Quote Link to comment Share on other sites More sharing options...
ariel_ht5_john Posted June 6, 2019 Report Share Posted June 6, 2019 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 . Quote Link to comment Share on other sites More sharing options...
Hydra Posted June 6, 2019 Author Report Share Posted June 6, 2019 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. Quote Link to comment Share on other sites More sharing options...
brian0304 Posted June 8, 2019 Report Share Posted June 8, 2019 Try it and get back to us with your findings ? Quote Link to comment Share on other sites More sharing options...
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