Rx7man
Cattle Rubbing Post
Wondering how you folks find the con rod length...
I found the deck height fairly easy to measure.. stroke can usually be found in references... piston height from pin centerline is easy.., but con rod length on an assembled bottom end is pretty tough.
so I measure squish with no base gasket
Add the piston crown to wrist pin centerline distance
and half the stroke...
From that, I subtract the deck height and the distance from the squish band to the mounting flange of the jug
I'm left with the con rod length.
Worded differently, The height the piston is at at the top of the travel is the (squish clearance) + (crown to pin height) + (Stroke/2) +( Con rod length) must equal (deck height) + (cylinder depth).
On a Jonsered 920 I come out to 68.5mm no matter how many times I do it.. which is a little funny to have a .5mm in there.. but oh well!
Anyone else have a better way that doesn't involve splitting the crankcase and crank?
I found the deck height fairly easy to measure.. stroke can usually be found in references... piston height from pin centerline is easy.., but con rod length on an assembled bottom end is pretty tough.
so I measure squish with no base gasket
Add the piston crown to wrist pin centerline distance
and half the stroke...
From that, I subtract the deck height and the distance from the squish band to the mounting flange of the jug
I'm left with the con rod length.
Worded differently, The height the piston is at at the top of the travel is the (squish clearance) + (crown to pin height) + (Stroke/2) +( Con rod length) must equal (deck height) + (cylinder depth).
On a Jonsered 920 I come out to 68.5mm no matter how many times I do it.. which is a little funny to have a .5mm in there.. but oh well!
Anyone else have a better way that doesn't involve splitting the crankcase and crank?