Stihl Ms660 56mm Project (Zeda Frankenstein) Now 54mm

Jag

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Oct 6, 2018
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191
Got the new cdi and mag on, still nothing. Took off my exhaust hit it with a torch and it caught fire. Soooo I’m still going to say it’s a spark problem because I have fuel that has not been combusted in my exhaust. Tried starting fluid too btw. I’ve gotten no life out of this engine so far
 
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Street Ryderz

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Oct 14, 2016
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3,046
It's probably cross talk leaving the cylinder short circuited,and yeah if it's not running there will be unspent fuel in the exhaust. Even with a similar stroke the geometry's are different with different dwell different time over area,this is why many don't try to do these type builds.
 

Street Ryderz

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Oct 14, 2016
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The ms660 is 54mm bore with 40mm stroke as factory specs suggest but it's not a 89 or 85 mm rod it has a different crank dia compared to ours and therefore the crank circle and rod length differ creating a hassle to match the geometry correctly.If you use a 40mm crank and can get the jug to sit where it allows the full stroke without cross talk it will run.
 

Jag

Active Member
Joined
Oct 6, 2018
Messages
191
The ms660 is 54mm bore with 40mm stroke as factory specs suggest but it's not a 89 or 85 mm rod it has a different crank dia compared to ours and therefore the crank circle and rod length differ creating a hassle to match the geometry correctly.If you use a 40mm crank and can get the jug to sit where it allows the full stroke without cross talk it will run.
Cross talk?
 

extremeodd

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Mar 30, 2019
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111
The ms660 is 54mm bore with 40mm stroke as factory specs suggest but it's not a 89 or 85 mm rod it has a different crank dia compared to ours and therefore the crank circle and rod length differ creating a hassle to match the geometry correctly.If you use a 40mm crank and can get the jug to sit where it allows the full stroke without cross talk it will run.
I wonder how much different the ms440/044 jug/piston would be with a 36mm stroke. It seems to be a far easier modification as there is no need to cut down the jug, all you should need is a spacer plate (under $30 at zms) and to fill/drill/tap the mounting studs.

Whenever I get a spare motor, I might try my hand at doing a ms440 frank if it is as simple as it seems.
 
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