How do you have the engines phased: alike, or #1 TDC ignition = #2 TDC overlap?
Left front cylinder fires degrees before the left rear cylinder...So it's like a big 360 degree twin so to speak...it's actually fairly smooth running, not radically tuned and idles like a stock Triumph at 900 rpm
On the dyno it made 93 HP @ 6000 rpm...and 95 HP at 7200 rpm....85 ft lbs torque@ 5400 rpm.....As suggested by Panic above, the exhaust pipes are too long causing the power curve to flatten out but the engines are still willing to rev freely to 7500 rpm.. I shortened them 4 inches, see how it goes at the track...50 RWHP is a decent number for a modified Triumph 650 engine with a more or less stock head with a careful valve job
The many runs on the dyno also tested the primary drive for durability...No problems