McCulloch 250 cylinder differences

jklw77

jklw77

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For you McCulloch hands ,working on a McCulloch , after getting a NOS cylinder , started to compare ports and was surprised to see how choked down new one was ,casting #640 left of rib ,only mark. old one no ribs on intake side, casting #62481 , .where reed plate insulator gasket goes 2 15/16" opening , new was 2 1/4" , with gussets in the opening .Transfer port , Old has 3 , 1/2 holes in the cylinder bore . New cylinder has 1, 1/4" hole in cylinder bore .Was blown away how different the openings were .I can only guess this new one is an early cylinder . Crazy choked down such a low flow , compared too old.
On other brand saws ( magnesium/ aluminum) ports usually pretty much look the same, for several years run.
 
heimannm

heimannm

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62481 is a 250, 640 is in fact a 640, different model altogether although they share many parts. The 640 is a gear drive, top tank saw and the 250 is a direct drive front tank saw. If you want 250 like performance you probably need to find another cylinder.

By the way, you will get a lot more attention if you post this in the McCulloch Chainsaw thread in the Stickies section.

Mark
 
serdie

serdie

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62481 is a 250, 640 is in fact a 640, different model altogether although they share many parts. The 640 is a gear drive, top tank saw and the 250 is a direct drive front tank saw. If you want 250 like performance you probably need to find another cylinder.

By the way, you will get a lot more attention if you post this in the McCulloch Chainsaw thread in the Stickies section.

Mark
If you’re working on a super 250 you’ll have to find the correct cylinder for it as they are a full on kart engine. The rest of the 250s usually have the port configuration of the replacement you have. Super 250s were 87 cc and really aggressive.
 
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