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Old August 13th, 2019, 03:14 PM   #5
DannoXYZ
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Name: AKA JacRyann
Location: Mesa, AZ
Join Date: Dec 2011

Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C

Posts: A lot.
MOTY - 2018, MOTM - Nov '17
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.

Last futzed with by DannoXYZ; August 14th, 2019 at 03:06 AM.
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