Neville Hill Posted July 24, 2017 Share Posted July 24, 2017 I have stripped the exhaust thread on a Saito 82a. Fitting a Helicoil is not feasible as there is insufficient casting round the original thread. Aluminium welding re-machining and re-tapping is a possibility but I am concerned about the heat involved. Another thought is to Loctite and oversized threaded male/female adaptor into the existing thread. Would it have to be steel or aluminium? Has anyone successfully done this repair. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted July 25, 2017 Share Posted July 25, 2017 Not something i've ever had to do so my guess is a steel adaptor. Quote Link to comment Share on other sites More sharing options...
Former Member Posted July 25, 2017 Share Posted July 25, 2017 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted July 25, 2017 Share Posted July 25, 2017 This has all been discussed on this site before Neville, And their is a chap that fits an insert available very reasonably priced And I cannot find the thread, but will Search helicoil, with a view not to fitting one, as in that thread is the new insert guy Found it Posted by Justin K. on 30/04/2017 06:58:33: I can thoroughly recommend Peter , his service is first class and the cost extremely reasonable. I had partial thread damage and didn't need an insert , he sent internal pictures of the head & thread and even test ran the engine for me , first class. **LINK** Edited By Denis Watkins on 25/07/2017 06:36:16 Quote Link to comment Share on other sites More sharing options...
Neville Hill Posted July 25, 2017 Author Share Posted July 25, 2017 Thanks for the information, I will contact him although his repair is to the glow plug thread and not the exhaust. Maybe he has a fix for this also. A mail to 'the wizard of Oz' is worth pursuing. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted July 25, 2017 Share Posted July 25, 2017 I think the above post with link is mainly for stripped glow plug threads . I haven't heard of a successful repair for the exhaust thread . The .last one I did needed a new cylinder / head . Welding would be out as associated heat would cause damage to the plating in the liner . you might be able to find someone who has the equipment to machine and fit adapter to the head but would probably cost as much as a new cylinder. Wizard of OZ ? could be a long walk up a yellow brick road and a wasted journey. Quote Link to comment Share on other sites More sharing options...
David Ovenden Posted July 25, 2017 Share Posted July 25, 2017 I believe that the thread on the Saito 82 exhaust is 12mm x 1mm pitch. IIRC the Saito 125 uses 13mm x 1mm pitch on its exhaust which is only 1mm bigger diameter. Maybe there is enough metal on your Saito 82 to tap out to 13mm (as it is the same TPI as the existing damaged thread) and then use a saito 125 exhaust. (Or tap out your muffler to 13mm too and then just buy a 13mm header pipe from a Saito 125?) I don't have a Saito 82 or Saito 125 to check with so I'm not sure how do-able it would be. Maybe Engine Doctor would know? Quote Link to comment Share on other sites More sharing options...
John Stainforth Posted July 25, 2017 Share Posted July 25, 2017 Posted by Engine Doctor on 25/07/2017 10:42:06: I think the above post with link is mainly for stripped glow plug threads . I haven't heard of a successful repair for the exhaust thread . The .last one I did needed a new cylinder / head . Welding would be out as associated heat would cause damage to the plating in the liner . you might be able to find someone who has the equipment to machine and fit adapter to the head but would probably cost as much as a new cylinder. Wizard of OZ ? could be a long walk up a yellow brick road and a wasted journey. Lee Custom Engines in the US renovates stripped exhaust threads in model engines including Saitos. He did a good job on one of mine. Once Saito exhausts start coming loose the problem tends to get worse. I've found that the best option is to immediately fit a Pitts-style muffler if the Saito pipe start coming loose. I have never had Pitts-style mufflers come loose. Just Engines also sells some other good alternatives. The standard exhausts on Saito engines are the one thing I don't like about them. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted July 25, 2017 Share Posted July 25, 2017 Posted by David Ovenden on 25/07/2017 11:09:18: I don't have a Saito 82 or Saito 125 to check with so I'm not sure how do-able it would be. Maybe Engine Doctor would know? Sorry cant help at the moment as i gave the damaged parts back to the owner so no parts to check if its doable . Quote Link to comment Share on other sites More sharing options...
Neville Hill Posted October 26, 2017 Author Share Posted October 26, 2017 Hi Everyone, thanks for all your advice. In the end I turned up a male aluminium hex adaptor with an oversize 12 x 1mm thread and a normal fit female 12 x 1mm thread on the other end. Screwing this into the engine head, no work was carried out on the stripped thread, with thread lock was successful and on running the engine on a test stand seemed to hold OK. If it will stand the rigors of actual flight remains to be seen, lets hope. Quote Link to comment Share on other sites More sharing options...
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