McCulloch 250 cylinder differences

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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.
 
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
 
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.
 
Super 250s are not kart engines and don't have magic ports. Irrelevant anyway because a 62481 block is a std 80cc 250 as Mark has said. They are very common.
 
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
will be using original 250 block 62481, with a .030 oversize piston .
 

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