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old sj 50


Old 07-26-2009, 09:07 PM
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Default old sj 50

I picked up an old sj 50.that been sitting around for years.it has an ss muffler and single needle valve on the carb.I dumped a little fuel through it to loosen it up and compression seems very good but the berings sound a little loud.well alot loud.but they turn very easy.I put it on my viper today and cranked it over.with a 8.5X7.5 it jumped right up to 18k could have gone more but I backed it off to 17 and flew it with no problems.should i get new berings?does jett still service this engine?also is that prop to small?it sure revs nice.
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Old 07-28-2009, 09:51 PM
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Default RE: old sj 50

Thanks for writing......

How old is it? Pre-1998 engines had a different crankcase. The bearings are the same - no problem replacing those. The piston/sleeve changed about then, and the old style parts are no longer available.... so as long as it runs well you should have no issue there either.

Jett can service the engine to replace the bearings if you desire.

Performance sounds good. The prop you have is great for a smaller aircraft or Q-500. Do not worry about too many rpm. With the SS muffler you are looking for 18K rpm and higher for ground peak. Props like a 9x7 standard blade MA or APC is always a good baseline and is good for most sport aircraft and the Viper as well. APC 8.75x8W 8.75x7.5 should work well too.
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