McCulloch 250 cylinder differences

[jklw77]

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]

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]

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.

 

[matt_lamb_160]

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.

 

[jklw77]

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 .