Andy wrote:I'm sure if something can be done with the nasty 150 exhaust manifold angle there are nothing but gains to be had, plus expansion chambers really need to be matched to the capacity/tune.

Matt seems to have ironed out the combustion chamber issues after we sent him an NSR500V head to measure up and cross-reference against 150 and 250 heads. We're still waiting for him to send us a motor to evaluate though!

Interestingly we tried straight exhaust spigots back to back with the bent ones and there was absolutely no difference. This was on the same bike, same day with same tune. It might be more "technically correct" to run the straight spigots but in reality there isn't a measurable difference in my opinion.

The combustion chamber shape is quite extreme compared to the Tyga inserts Matt sells, but there is no way he could sell what we run as a product, there would be holled pistons everywhere! They are designed around a 38m/s maximum squish velocity. We also run the plug much closer to the piston with the electrode sitting 6mm away from the crown of the piston at TDC. The heads gave us some big gains particularly in mid range performance, but I do have a suspicion that we have gone too high in comp.