Crankshaft degrees-piston travel

Message

oldracer · #1 Post by **oldracer** » Sat Jul 14, 2007 12:08 pm

I know I'm being lazy and could put a degree wheel on the crank and measure the piston travel with an indicator but I believe there was a conversion chart published on this forum some time ago, does anyone have it or know where I can find it?
Thanks, oldracer

beebe · #2 Post by **beebe** » Tue Jul 17, 2007 12:01 am

A = COS[(P^2 + R^2 - L^2) / (2 x P x R)]

A : Ignition advance (degrees)
R : Engine stroke divided my 2 in mm
L : Con rod length in mm
T : Ignition timing in mm
P : R + L - T

I made a little spreadsheet that does it for me, so if you need any specific numbers, let me know.

oldracer · #3 Post by **oldracer** » Wed Jul 18, 2007 1:10 pm

Thanks beebe, this is exactly the information I am looking for. Could you let me know the linear measurement, (piston travel) for: 24,22,21,18,17and 9 degrees before T.D.C.
I have a Motoplat ignition which does retard the timing as the revs increase, according to the strobe light anyway, and I want to put some scribe lines on the rotor in order that I can see where the spark is occuring in comparison to the chart in the shop manual.
Thanks again,
oldracer.

beebe · #4 Post by **beebe** » Thu Jul 19, 2007 2:12 am

What bike? RZ?

beebe · #5 Post by **beebe** » Thu Jul 19, 2007 3:02 am

For the RZ:
Con rod length = 110mm
Stroke 54mm

"Advance" = "mm"
24deg = 2.884mm
22deg = 2.432
21deg = 2.220
18deg = 1.638
17deg = 1.463
9deg = 0.414

oldracer · #6 Post by **oldracer** » Thu Jul 19, 2007 10:24 pm

Thanks beebe, the bike is an RZ350 and the figures you gave me are exactly what I wanted.
oldracer