Author Topic: exhaust leak on #4  (Read 787 times)

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Offline judder

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exhaust leak on #4
« on: March 19, 2012, 08:26:22 AM »
I put a new exhaust on the bike with new copper crush washers ( I took the old ones out) and now I've got a leak on #4. There didn't seem to be any damage to the head or the pipe so I really don't know what is happening. So my question is would there be a problem with using the existing crushed (new) gasket and adding another new copper gasket to that one cylinder? Any other ideas on how I can get her to stop leaking. The pipe is still on the bike now, I'm just in the thinking stage.

Thanks

Jud
1974 CB750 K4 cafe project bike
1990 Harley Davidson FXSTS

Offline mrrch

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Re: exhaust leak on #4
« Reply #1 on: March 19, 2012, 08:34:14 AM »
Are you sure you got all the old ones out?
I've seen some so coated in carbon and soot  that they blend into the head.
I pulled 3 out of exhaust hole on a head I rebuilt.
my build

1977 CB750K WITH 1976 CB750F ENGINE

Offline judder

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Re: exhaust leak on #4
« Reply #2 on: March 19, 2012, 08:40:13 AM »
I'm pretty sure but maybe there is another one in there and maybe more across all cylinders. I guess I will take everything back apart pick up some new gaskets and make sure everything is out and start fresh. I had a hell of a time getting the pipe on so I was hoping to do it the easy way. The easy way never works.

Thanks
Jud
1974 CB750 K4 cafe project bike
1990 Harley Davidson FXSTS

Offline mrrch

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Re: exhaust leak on #4
« Reply #3 on: March 19, 2012, 09:18:56 AM »
Take a look at the headers and see if one is bent/positioned a little differently compared to the opposite side.
my build

1977 CB750K WITH 1976 CB750F ENGINE

Offline ANVkevin

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Re: exhaust leak on #4
« Reply #4 on: March 19, 2012, 10:00:11 AM »
I had the same issue. Turns out my split ring sleeves were worn and needed replacing. They were barely touching the copper gaskets, so I'm not worried about replacing the copper. What helped (prior to replacing those split rings) was tapping the header with a rubber mallet until i was certain it was seated. I then ran the bike for a few minutes (up to operating temp) and tightened the bolts from there.