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I have been doing some thinking about cam timing and assuming we don't use came phasers (which I believe we realistically can't) I believe we need at least 295° cams :
20° advance + 180° + 95° retard
I am not very sharp on bike cams but it doesn't seem too wild (the hot factory cam for beemer airheads are 336 IIRC) at least for 2 valvers.
As for FE, on top of Atkinson timing on the inlet, we don't want a lot of overlap to promote low RPM efficiency as well as not too much duration on the exhaust (that's where we might need a regrind).
The timing of my particular bike is 260 on the inlet.
I think I will investigate 2 valver timing of the same base engine.
GN 400's and 125 are on the top of the list.
By the way, I could build a nice 12,2 to 1 CR engine with a DRZ 250 head and barrel on top of a DR 350 bottom.
Anybody can find the DRZ 250 (complete) head and piston + barrel in the US ?
Last edited by renault_megane_dci; 10-20-2012 at 05:26 PM..
Reason: duration ON THE EXHAUST
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