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03 cr250 exhaust flange. And O-rings

By MotoGuido,
in Honda 2 Stroke

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MotoGuido

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Are there different size flanges for this model!?

Always had a slight leak here during warm up. Bought o-rings straight from honda and they were so thick when installing the pipe it just pushed them out of their groove and up the flange.

The o-rings I removed were flat but I assume that's just how they ended up over time.

Pipe is a pro circuit works. I've been after them for a while now trying to figure out if it's the right flange!?

Both the ID on the pipe and the OD on the flange measure ~48mm. Flange is steel.

Thanks

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hawaii500_1999

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i think the 02 pipe is different then the 03 and up.  maybe check part numbers for the flanges as well.

 

with that said i bought an aftermarket one when i broke mine and i think it covered all years.

 

 

also with the o rings.  yes they got flat from use.  they are supposed to be round.

 

as for them slipping mine did that too, i either used some high temp anti-sieze one them, or i siliconed them.  the silicone was slippery before it cured.

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shrubitup

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I use the Pro Circuit flange w stock o-ring and don't have a problem. Supposedly the stock flange is brittle junk and should be replaced. But I wouldn't bother replacing until it actually breaks.

Oem is very brittle - installing one spring on mine tore it apart. I bought a pro circuit flange too. Much stronger.

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MotoGuido

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I use the Pro Circuit flange w stock o-ring and don't have a problem. Supposedly the stock flange is brittle junk and should be replaced. But I wouldn't bother replacing until it actually breaks.

Pipe was on the bike when I bought it. Not sure if this is pro circuit flange or factory flange lol.

Here's what they said:

"We're still investigating your pipe flange issue. Because our inventory of

this item is at zero, we're having our machine shop make a few to confirm

the finished products are to the correct specifications.

We'll keep you up to date.

Thanks.

Pro Circuit Products"

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Redlined

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My '02 flange looked exactly like that, the o-ring was flat and I assumed it was supposed to be because it fit the width of the o-ring groove machined in the flange. I reused the o-ring with high-temp RTV on it, no issues. I wrapped a Gnarley pipe around the frame and it broke the OEM flange. The local Honda dealer actually had a flange in stock, it was like $17 and got me going for riding the next weekend. I ran that bike 6 years and never had a problem with the flange on normal pipe impacts, something had to give on the one that did do it in. I didn't see the benefit of a higher cost flange.

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MotoGuido

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I've looked at this many times. It looks like a really nice piece! However,  the fix I've read about is only for the D-shaped ports on the '04 and possibly later.  

 

My cylinder has a round port and matches the round flange. 

 

Just spent $1k on fixing the inherent problems with the top end.... so I was hoping to just leave the damn flange alone lol!!

Edited by MotoGuido
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MotoGuido

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My '02 flange looked exactly like that, the o-ring was flat and I assumed it was supposed to be because it fit the width of the o-ring groove machined in the flange. I reused the o-ring with high-temp RTV on it, no issues. I wrapped a Gnarley pipe around the frame and it broke the OEM flange. The local Honda dealer actually had a flange in stock, it was like $17 and got me going for riding the next weekend. I ran that bike 6 years and never had a problem with the flange on normal pipe impacts, something had to give on the one that did do it in. I didn't see the benefit of a higher cost flange.

 

Better the flange than the cylinder!!!!  You got me thinkin maybe the brittle stocker isn't so bad to have!  Just spent $1k on my top end if something happens to it you can't get a new one off the shelf now with all the custom shit that's done to it wow that's a bad thought..

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MotoGuido

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I leave my damn flange alone. It leaks and I don't care anymore lol. I clean it up and spray some oily coating on it to make it clean easier the next time. Maybe one day when I'm bored I'll go find a o-ring that fits.

 

I wadded it up going wide open in 3rd gear and bent my Pro Circuit pipe to hell. Had it sealed up with RTV before this but now it was so crooked it couldn't be sealed really at all so I just rode it with a slight leak like you're describing.  

 

Was alright for a few months but in June my ring came apart right in front of the exhaust bridge and tore the shit out of the cylinder wall removing plating etc.  Tuner said that cold air entering the cylinder here from the leak likely could have contributed to making that a weak point.  

 

If I were you I'd at least seal it up.  My bike is gonna shred now but it cost my big $$$$ and I wasn't ready to spend that in the middle of summer.  Could have fixed it stock but it still would have ran about $600 so I said fugg it I'm goin balls deep.

 

Had pipe straightened by Pacific Crest Pipe Repair.  Not cheap either after shipping but came out pretty!

Edited by MotoGuido
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runnybunny

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I wadded it up going wide open in 3rd gear and bent my Pro Circuit pipe to hell. Had it sealed up with RTV before this but now it was so crooked it couldn't be sealed really at all so I just rode it with a slight leak like you're describing.

Was alright for a few months but in June my ring came apart right in front of the exhaust bridge and tore the shit out of the cylinder wall removing plating etc. Tuner said that cold air entering the cylinder here from the leak likely could have contributed to making that a weak point.

If I were you I'd at least seal it up. My bike is gonna shred now but it cost my big $$$$ and I wasn't ready to spend that in the middle of summer. Could have fixed it stock but it still would have ran about $600 so I said fugg it I'm goin balls deep.

Had pipe straightened by Pacific Crest Pipe Repair. Not cheap either after shipping but came out pretty!

Good tip. Maybe I'll fix it then!

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