Hip to be square
MG finally gets his Us-sourced ‘square cam’ in the FXR. It even ticks over. Just…
RUNNING IN PLEASE PASS. You don’t see that so often, if at all, these days. It’s refreshing to know that some things stay the same with old V-twin knockers – you have to run things in. Especially when a 1340cc mill has been treated to a wild cam, new followers, a glaze bust on the bores, and new rings. It’s been a long time coming this refresh of a tired Evo engine in its first gen 1984 FXR chassis, but it already feels like it’s worth the long-ish (two year) wait. All down to me. The Leineweber E4S cam is by no means the most brutish this longestablished line of cam grinders produce. But it goes some way to reinforce Jim Leineweber’s rep. as the ‘man who makes square cams’. By square we mean a ramp that gets the valves off their seats as rapidly as possible, holds them close to maximum lift for as long as feasible, and then dumps them back on their faces in short shrift. And this cam has lift too: 0.528in of it. ‘Our highest lift bolt-in cam’ they say. It’s not exactly bolt-in. Rich at Skullchopa (sic) had to relieve the cut-outs in the pistons for safe valve-to-valve clearance and Alex at Fastlane Heads was most concerned we might not have enough cranking compression to make it work properly at a conservative 9.25:1 static ratio (ideally it wants 10:1), but it seems to be working sprightly enough for me to have to clamp up the clutch springs a few times to stop it slipping even at well under a 4000rpm (ish) running-in ceiling. It feels like it wants to go. I’ll change oil and filter after 400 miles and then gently get it towards the 6000rpm max we’ve dialled-in via the Crane Hi-4 ignition curve. Next stop dyno fine-tuning and the roller of truth. Feels good. Real good. It even ticks over. Just.
MG’S new square cam. Not exactly bolt-in