EX250 - 1ST-GEN '86-87
3.1cm = diameter at exhaust port outlet
31.5cm = left header length
31.5cm = right header length
3.15cm = diameter after merge
3.2 = diameter just before muffler
EX500 - '95-09
3.5cm = diameter at exhaust port outlet
59cm = left header length
59cm = right header length
3.5cm = diameter after merge
3.5cm = diameter just before muffler
DISCUSSION
One thing I noticed with new-gen exhausts was difference in header-length between #1 and #2 cylinders. Anyone know why? I suspect it has something to do with uneven firing-order.
All new-gen exhausts has pipe that slides into 2.75cm opening of exhaust-port, causing reduction in diameter. This would appear to be more restrictive design than pre-gen/EX500 exhausts which butts up header-pipe to outside of exhaust-port without narrowing it down. Wondering if modifying new-gen exhaust to be similar would yield some gains. After all, it doesn't matter if you open up header-pipe to 28 or 31mm afterwards, exhaust still has to squeeze through 25mm bottleneck just to get out of exhaust ports.