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McCulloch 10 10 diagnostic help needed

Willoughby

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I recently acquired a pro mac 850 …good spark 60 psi ... tearing down now to clean and inspect
 

Steve

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I recently acquired a pro mac 850 …good spark 60 psi ... tearing down now to clean and inspect


Check to make sure the decompression is sealing first. They are known to leak.
 

Willoughby

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Check to make sure the decompression is sealing first. They are known to leak.
when I got it the plug wire was off and the throttle was stuck wide open …...looking through exhaust port the piston looks pretty scored and the rings appear to be stuck , Im hoping a piston will fix it I found a new old stock piston with rings ill know more next time I get to work on it when piston gets here , I really appreciate your help Steve- thanks a bunch by the way I have a retired logger friend who told me he has 2 NIB pro 800s? and when our local MCculloch dealer closed in 97? he bought 1k worth of parts -he said he never ran anything but macs & never would hes not doing too good hes 84 - I need to go see him soon -really neet man
 

Steve

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when I got it the plug wire was off and the throttle was stuck wide open …...looking through exhaust port the piston looks pretty scored and the rings appear to be stuck , Im hoping a piston will fix it I found a new old stock piston with rings ill know more next time I get to work on it when piston gets here , I really appreciate your help Steve- thanks a bunch by the way I have a retired logger friend who told me he has 2 NIB pro 800s? and when our local MCculloch dealer closed in 97? he bought 1k worth of parts -he said he never ran anything but macs & never would hes not doing too good hes 84 - I need to go see him soon -really neet man


Thats a real neat story. Carefull cleaning the cylinder up. McCullochs where not known for real strong plating. Im pulling for you though!
 

Willoughby

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I got it apart today the piston is heavily scored on exhaust side but looks great on intake side, on the exhaust side of cylinder above exhaust port it feels better than it looks , if I try I can just barely feel 1 spot that my 90 pick cand
feel & catch on a bit -I have a piston coming -I cant see how to get pin out of rod & piston ? I could use some insight on this . and should I hone the cylinder or just leave as is ? -I can make the gaskets needed but Id like to find a pulse tube if possible the bearings feel good but I cant seem to see the seals ?, there are some lips or ridges in the exhaust port that needs removed also -all help appreciated
 

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The piston pin is press fit to the rod. Press it out, heat the rod to 300 Fahrenheit, press the pin back in. Do not hone the cylinder. The best way to remove transfer is the Mastermind way with emery cloth and scotch brite. Search youtube for his video. Seals are national 471551 and 253747.
 

Willoughby

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The piston pin is press fit to the rod. Press it out, heat the rod to 300 Fahrenheit, press the pin back in. Do not hone the cylinder. The best way to remove transfer is the Mastermind way with emery cloth and scotch brite. Search youtube for his video. Seals are national 471551 and 253747.
thanks , getting the tank off was tough with the oiler and choke rods in the way of the av mounts there has to be a better way to re install ? and where could I find seals and a pulse tube -google ?
 

Steve

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thanks , getting the tank off was tough with the oiler and choke rods in the way of the av mounts there has to be a better way to re install ? and where could I find seals and a pulse tube -google ?

Ebay is most likely the easiest. The seals you should be able to get at any auto parts store.
 
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