450 250 interchangeable parts - Honda Rebel Forum
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post #1 of 14 Old 06-29-2011, 02:55 PM Thread Starter
 
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450 250 interchangeable parts

I was wondering how interchangeable the parts for 450's and 250's are. Specifically, are the fenders and gas tanks the same size?

I know the 450 is a little bigger, but is it that much different (cosmetically at least)?

1986 Honda Rebel 250
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post #2 of 14 Old 06-29-2011, 03:09 PM
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The 250 and the 450 are two completely different machines.
While they share a name and some strong family resemblance, that's about it.
For original equipment stuff about the only things that are direct bolt over and same wiring are the rear turn signals. The front signals for a 450 have running light OE and the 3590 does not. The turn signal lenses are 100 percent interchangeable.
That's about it!
The tanks mount differently. The 450 uses a vacuum petcock, the 250 a gravity feed.
The 250 petcock will thread in to the 450 tank.
The forks are different and the swing arms are different. Fenders will not be a straight bolt across.




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post #3 of 14 Old 06-29-2011, 03:32 PM
 
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The tanks mount differently. The 450 uses a vacuum petcock, the 250 a gravity feed.
The 250 petcock will thread in to the 450 tank.
So then a 450 petcock will mount up to a 250 tank?

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post #4 of 14 Old 06-29-2011, 03:52 PM
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I should, but why would you want to?




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post #5 of 14 Old 06-29-2011, 03:55 PM
 
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So then a 450 petcock will mount up to a 250 tank?

No, because cmx450 petcock needs vacuum port to allow fuel. as far as I know cmx250 doesnt have any such provision for a vacuum port

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post #6 of 14 Old 06-29-2011, 04:01 PM
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It would still mount to the tank, he never said it had to work...




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post #7 of 14 Old 06-29-2011, 04:20 PM
 
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Originally Posted by Buickguy View Post
I should, but why would you want to?
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Originally Posted by mohanpiyush View Post
No, because cmx450 petcock needs vacuum port to allow fuel. as far as I know cmx250 doesnt have any such provision for a vacuum port
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Originally Posted by Buickguy View Post
It would still mount to the tank, he never said it had to work...
Just thinking out loud
Where does the vacuum port on the 450 get its vacuum? Through the intake port?

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post #8 of 14 Old 06-29-2011, 08:10 PM
 
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The problem I find with using a 250 petcock on a 450 isn't so much a matter of vacuum vs not, but rather fuel flow. The 250 petcock is 3/16" diameter. not much fuel needed for a single carb. The 450 is 5/16", needing double the fuel flow to feed two carbs and a larger appetite.

Ther are people that have successfully converted the 450 petcock to a gravity fed by blocking off the vacuum diaphram (solid plate) and plugging the line from the head. IIRC, it was recommended to do an overhaul of the whole thing to make sure there were no restrictions. YMMV

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post #9 of 14 Old 03-22-2017, 12:06 PM
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wondering if the turn signals wiring assembly in the 250 interchange???
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post #10 of 14 Old 11-19-2018, 04:53 PM
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needed new tank

Quote:
Originally Posted by Buickguy View Post
I should, but why would you want to?
Just joining the chat, but for me the "why" is because I am retrofitting a 250 tank for my 1986 450. I still need the 450 petcock though for proper fuel flow for the dual carburetors. My question is will the 450 petcock leak if put into a 250 tank without mods? (The original 450 tank has a plastic insert that the 250 one does NOT have and I am afraid of any leakage or vacuum loss)
(p.s. I am using a tank with an overflow that acts as a vacuum)

Thanks for any help
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