02-04 CR250 Boyesen exhaust flange

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4/5/2020 2:15 PM
Edited Date/Time: 4/6/2020 8:30 PM

Boyesen 04 exhaust flange $85
951-813-8949
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4/5/2020 2:29 PM

How much for just the Hinson cover ?

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Speak softly and carry a big stick.

4/5/2020 2:43 PM

H4L wrote:

How much for just the Hinson cover ?

$100

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4/6/2020 3:54 AM

Sent a pm

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4/6/2020 2:36 PM

Clutch and ignition cover SOLD

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4/6/2020 8:31 PM

Updated

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4/7/2020 11:07 AM

what's the difference between a 03 and 04 flange???

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4/7/2020 11:16 AM

booma1218 wrote:

what's the difference between a 03 and 04 flange???

Found this on a google search.

Get one of the Boyesen exhaust flanges while you still can. If you don't think it will make a difference, take off the stock one and look at the shape of the exhaust port - the port is D-shaped (laying on its side) and the stock flange is round! This is an uncharacteristic engineering oversight or manufacturing shortcut (at least for Honda) - I'd estimate 30% of the area is mismatched. The Boyesen flange is a work of art and matches the port shape exactly. I, too, looked for a less expensive option. I looked at the Pro Circuit part - it's stronger, but it's still just round - it does NOT match the port like the Boyesen part. I couldn't find it anywhere but Boyesen. Trust me, it's worth it. Combined with one more tooth on the rear sprocket, a RAD valve and a JD kit, the bike is now an absolute beast, and feels nothing like the stock motor. It went from mellow and smooth but strong to a real eye-watering arm-stretcher.

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4/7/2020 10:00 PM

booma1218 wrote:

what's the difference between a 03 and 04 flange???

The 02-03 Cyl. have a round exhaust port & the 04 has an oval exhaust port. The 05-07 don't use an exhaust flange since it has a redesigned cyl.. On those yrs.Honda used a male expansion chamber end where it went into the cyl. exhaust port.

Here is a pic of an 04 cyl. exhaust port. So the flange being sold is only designed for an 04 model as the box sticker indicates above.

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Speak softly and carry a big stick.

4/7/2020 10:03 PM

booma1218 wrote:

what's the difference between a 03 and 04 flange???

H4L wrote:

The 02-03 Cyl. have a round exhaust port & the 04 has an oval exhaust port. The 05-07 don't use an exhaust flange since it has a redesigned cyl.. On those yrs.Honda used a male expansion chamber end where it went into the cyl. exhaust port.

Here is a pic of an 04 cyl. exhaust port. So the flange being sold is only designed for an 04 model as the box sticker indicates above.

Photo.

Thanks H4L! I’ll update

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4/8/2020 6:55 AM
Edited Date/Time: 4/8/2020 6:10 PM

GouldRacing25 wrote:

Thanks H4L! I’ll update

FYI - The 02-03 Boyesen exhaust flange is round (have one) like the oem at the opening where it bolts up to the cyl..
The 04 Boyesen exhaust flange is oval like the oem cyl. to match the exhaust port.
I think Honda used the 03 model round exhaust flange on the 04’s from factory. I was told that Honda was trying to cause a turbulence effect on the 04 exhaust port area by using the round flange. Supposedly that was the reason for the mismatch on the exhaust flange for the 04 model. Don’t know if that is fact or fiction.

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Speak softly and carry a big stick.