pstebbins1108

1986 CMX 450 Rebel. Off the petcock there is a vacuum line. What does that attach to? This was not attached when we got the bike and of course it's running rough. Thanks.

Pat

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JunkyardDog

I was not aware the 450 had a vacuum operated petcock. But if it does, there will be a vacuum fitting probably on the left carb or intake manifold that it is supposed to connect to, unless it is broken off. If is a vacuum petcock, it shouldn't even run if it is disconnected, since it requires vacuum to open the petcock and get gas to the carbs. Also, if it is running, not only is there a problem with the petcock, but you have a vacuum leak somewhere, wherever the other end of that hose is supposed to be attached too.

There is one more possibility. It's possible the vacuum diaphragm in the petcock failed, and the petcock is open all the time, so a previous owner may have disconnected the vacuum line and plugged the fitting where it went to. I'm sure someone with a 450 will show up soon and be able to answer your question. Jerry.

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cagie

Looking at the diagram for the 450 petcock it sure looks like it's vacuum operated, but it also has a manual valve (On Off Res). Looks like Jerry could be right and the diaphram is shot.

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Comments contained in my posts are not intended to cause physical or psychological stress and are mearly my two cents worth, and in this economy, that's cheap!
87 CMX250C 'the Pygmy Pony'
87 CMX450C 'Black Lithium'

JunkyardDog

Yes, it is a vacuum petcock. Hopefully it is not leaking gas. These petcocks are no longer available. Disconnect the fuel hose from it, turn it on, and see if gas comes out. If it does, the vacuum diaphragm is shot. The good thing is that it will run that way if you plug up the vacuum connections on the petcock and wherever that line goes to. If it leaks gas at the petcock, there is a way of stopping the leak, but it makes the petcock unable to be shut off, unless you can find parts.

The $70 petcock on my dirt bike started leaking, and I fixed it that way. Now if I want to shut off gas to the carb, I have to pull the fuel line off the petcock and put a rubber vacuum cap on it. A bit of a hassle, but better than spending $70. Jerry.

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GearJammer

Yes, the 450 Reb has a vacuum acuated petcock. The vacuum line that you're asking about connects to a fitting on the lower, left backside of the cylinder head, just in front of the left manifold.

It's been awhile, but wanted to pop in and offer some assistance here....

Best Regards to All and especially to CTC! Right on, Brother! You've seen your vision thru and have done an EXCELLENT job here with the site.....Respects to All......

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"Ridin' Ain't A Hobby, It's A Lifestyle"

1986 450 Rebel

Guba

Don't be a stranger GearJammer, after all, you helped build this forum!

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Some days beer tastes good...other days beer tastes better!

'07 Rebel 250 26,000 miles

GearJammer

Thanx very much, Guba......I appreciate your kind words, but this site was CTC's vision and he's had the persistence to see it thru and he is to be commended.

The site has grown a LOT since last I checked in, your membership looks solid and CTC has chosen some right on Moderators, so I commend you as well. Keep up the good work!

Life is busy here, but will try to stop in to assist if I can and will probably touch base with CTC in the near future.......Ride Safe, Guba & All.......

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"Ridin' Ain't A Hobby, It's A Lifestyle"

1986 450 Rebel

cagie

Keep the rubnner side down Gear! Glad you're still kickin'

__________________
Comments contained in my posts are not intended to cause physical or psychological stress and are mearly my two cents worth, and in this economy, that's cheap!
87 CMX250C 'the Pygmy Pony'
87 CMX450C 'Black Lithium'

jax

The vacuum line goes to the small pipe that is on the back of the left head if you are sitting on the bike. Ebay has some rebuild kits for the vacuum part of the petcock. Not to expensive and they work. I have rebuilt 2 petcocks using the kits. Just check under Honda Rebel 450 parts on ebay and you should be able to find them.

Ride safe

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GearJammer

Will do, cagie, and thanx! You please do the same....I've gotta take a look at my account and play some catch-up here.......

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"Ridin' Ain't A Hobby, It's A Lifestyle"

1986 450 Rebel