660 port smoothing

[xxl]

I have a ms 660. I rebuilt the the top end. New piston same cylinder. Still parts. The only thing I did was I smoothed all the ports. This saw runs at 12.8k. It just seems very zippy. Also out runs my bone stock 660. Dose smoothing the ports really make this much difference?

 

[vquinoveva]

I have a ms 660. I rebuilt the the top end. New piston same cylinder. Still parts. The only thing I did was I smoothed all the ports. This saw runs at 12.8k. It just seems very zippy. Also out runs my bone stock 660. Dose smoothing the ports really make this much difference?

12.8 k in the cut?


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[cookies]

remove the plug and insert a section of solder into the cylinder and smash it using the piston then measure thickness to get your approx squish on both saws. I have a feeling the zippy saw has around .030ish vs the non zippy having around .046ish. It can also be from carb settings being spot on vs set too rich.

 

[xxl]

out of the cut

 

[vquinoveva]

out of the cut

My understanding is thats just about spec just free spinning ,smoothing can help but I don’t have a reference point for the saw to say one way or the other


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[xxl]

remove the plug and insert a section of solder into the cylinder and smash it using the piston then measure thickness to get your approx squish on both saws. I have a feeling the zippy saw has around .030ish vs the non zippy having around .046ish. It can also be from carb settings being spot on vs set too rich.

They changed the squish on them ? I didn't lower anything

 

[vquinoveva]

They changed the squish on them ? I didn't lower anything

Did you remove the base gasket when you ground on the cylinder?


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[cookies]

They changed the squish on them ? I didn't lower anything

It varies from cylinder to cylinder due to casting mold changes. I have seen .028-.52 squish in oem cylinders

 

[huskihl]

The latest 660 I worked on was a head slapper without the gasket.

 

[xxl]

It has the base gasket

 

[link]

I did a lot of port smoothing on my up-juiced 50cc mopeds back in the days, the result was perhaps that it ran downhill slightly faster, not a power increase.
But I like the idea of how an engine works and if I can make it a little better I will.