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Slanted 660

mdavlee

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that changes with crank angle, just saying



I have a stock oem 660 cylinder with an ex dur of 160 no gasket. find a good one every now and then
It sure does. I think I measured that at exhaust area openings if I remember right. Been a long time.
 

stihl_head1982

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Are you guys lighting quarter sticks off over at your folks house? We're at the school...I peed a little.

It sounds like a war zone over here since dark. I guess the cops give a bit of a space of grace on this day. Exploding fireworks are supposed to be illegal in this state.
All is well, no use to disturb the old kiddos while they are having fun.
 

drf256

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So the piston is going the fastest at 90 and 270, correct?
It's always 90 Mike. It's a 2 stroke, not a 4 stroke. Once I got through my thick head it made stuff a lot less confusing. There's no BTDC or ATDC like on a 4 stroke.

The torquesoft and Lambretta software requires connecting rod length and stroke and factors in rod angle. It correctly calculates the port openings and factors in piston movement differences during different degrees of rotation. The best part is that connect rod length is very forgiving, so if you're off when you measure, it changes the port height calculation very little.
 

drf256

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It's out of round at the bottom, further up in the bore seems ok. I have about .002 - .003 ring gap up there.

The narrow side of the jug at the bottom is between the trans. Once I get the piston by the narrow part. It shouldn't touch the skirts
Aren't some jugs purposely out of round cold on purpose? Or am I thinking pistons?

I doubt that they are high tech enough for purposeful out-of-round so that it's symmetric upon heating up to operating temps.
 

Deets066

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Aren't some jugs purposely out of round cold on purpose? Or am I thinking pistons?

I doubt that they are high tech enough for purposeful out-of-round so that it's symmetric upon heating up to operating temps.
the piston only fits in the bore one direction. It won't go if it's turned 90*
 

Al Smith

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Aren't some jugs purposely out of round cold on purpose? Or am I thinking pistons?

.
The cylinder is round,the piston has taper from below the rings outwards towards the skirt and ovality .Now I'm talking a standard automotive type piston .I have no idea on a 2 cycle if that applies or not.
In my years in or around the automotive business I've worked on 4 different piston lines for Ford and installed one for Honda .Not much has changed except now of days they about all use coated pistons . Pistons like other components have evolved over the years,it's interesting
 

Deets066

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The cylinder is round,the piston has taper from below the rings outwards towards the skirt and ovality .Now I'm talking a standard automotive type piston .I have no idea on a 2 cycle if that applies or not.
In my years in or around the automotive business I've worked on 4 different piston lines for Ford and installed one for Honda .Not much has changed except now of days they about all use coated pistons . Pistons like other components have evolved over the years,it's interesting
Trust me, the cylinder is out of round. It's .010 narrower on one side
 
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