Cant sustain idle on 1979 Honda cb750

[weaseltree19]

Hey there.  I own a 1979 Honda cb 750 and I've got a problem with it.  I cant seem to be able to idle the bike at anything less than 2000 rpms after I start a ride.  The left two exhaust pipes on the 4 into 1 are a bit loose despite the screws being tightened all the way.  When I put my hand in front of the exhaust I feel exhaust hitting my hand, so I'm guessing I've got a leak.  Any ideas on how to fix this or solutions?  

Thanks mates

[shinyribs]

A hanging idle is almost always a vacuum leak. The easiest way to look for a vacuum leak is with a bottle is starting fluid ( or an unlit propane torch). Just spray the fluid around the carb boots and such and listen for a raise in rpm. Don't fog the area, just normal squirts. A little starting fluid goes a looong way.

Your headers seal to the head with hollow copper rings that get crushed between the pipe and the cylinder head. Might as well but a full set of four ( I think that's the only way they come anyway) as the entire 4-1 will come off to fix this. Be sure to dig out any old crush rings as they are often hard to spot through all the soot. But if you look and scratch around with a screwdriver you'll see them easily enough.

If you'll be a while getting to it, start spraying some pb Blaster on the exhaust studs now so it can be doing it's magic.

[weaseltree19]

Are we talking these guys right here?

http://www.ebay.com/itm/like/361375315855?ul_noapp=true&chn=ps&lpid=82

[TOOLS1]

Those look like they have been cut out of gasket material. You can still get the correct ones at your local Honda dealer, or vintagecb750supply.com cb750supply.com cyclex.com and several other sources.
TOOLS

[weaseltree19]

First ones?

[shinyribs]

I'm not familiar with the first ones. They may be superior, but I have no idea. The second ones, the copper ones, are what I've always found/used and have had 100% success with.

[TOOLS1]

I have used both, can't say one is better then the other.
TOOL

[shinyribs]

TOOLS1 wrote

I have used both, can't say one is better then the other.
TOOL

What are the top ones? Multi layered steel?

[TOOLS1]

shinyribs wrote

TOOLS1 wrote

I have used both, can't say one is better then the other.
TOOL

What are the top ones? Multi layered steel?

I think they are accordion.
TOOLS

[shinyribs]

Oh, ok. You can see the welded joint in the pic. Doesn't seem like that would compress well, but good to know there are other options out there.