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Author Topic: Rebuilt engine, leaking under valve cover  (Read 1049 times)

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Offline bompxc

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Rebuilt engine, leaking under valve cover
« on: September 06, 2014, 06:39:21 PM »
My K4 has finally been out back together and everything seemed to be in place, however I've found a dreaded oil leak! Two actually, one behind the the valve cover, one in front, both in the middle. Bolts are tight. The engine takes a few kicks to start, while it previously started on the first kick. It idles a bit erratically and eventually dies if I don't touch the throttle. Any help would be much appreciated. Just a bad seal? It's a new gasket. Please tell me it's possible without taking the whole engine out! The fourth photo is the oil that comes out after running it for three minutes.
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1974 CB750, K4.  Stock as can be, with the exception of 1975 CB750F Keihins.

Offline flybox1

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Re: Rebuilt engine, leaking under valve cover
« Reply #1 on: September 06, 2014, 06:45:50 PM »
What type of valve cover gasket did you use, and did you get installed correctly?  It's not symmetrical, but it looks like it.  Typically these are notched on the inside edge, and this notch needs to be positioned by the #1 cyl.
An upside down gasket will cause leaks between #2 in the front, right around the plug cutouts...

See my review here, and enlarge the gasket photo to see the notch..

http://4into1.com/vesrah-valve-cover-gasket-vv-1003-honda-cb750/


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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

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1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

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Offline bompxc

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Re: Rebuilt engine, leaking under valve cover
« Reply #2 on: September 06, 2014, 06:53:27 PM »
Damn.  I purchased the same gasket from the same site, however I'm not 100% sure I placed the notch in the right spot.  Would that also cause the engine to run erratically like it is?  I'm also going to purchase the allen head bolts for the valve covers.  I used the old phillips head ones and they may not be torqued all the way...
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1974 CB750, K4.  Stock as can be, with the exception of 1975 CB750F Keihins.

Offline bompxc

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Re: Rebuilt engine, leaking under valve cover
« Reply #3 on: September 06, 2014, 07:45:33 PM »
I haven't touched the carbs and they ran fine before? Just removed the gasket and found two things. Looks like it wasn't vesrah because there was no notch. And second, it looks like I was a little too hasty and foolish and lined up the holes a bit off... Broke thru in multiple spots
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1974 CB750, K4.  Stock as can be, with the exception of 1975 CB750F Keihins.

Offline flybox1

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Re: Rebuilt engine, leaking under valve cover
« Reply #4 on: September 06, 2014, 10:11:27 PM »
Yeah...if it's upside down, the holes are misaligned.
Notched or not, you'll need to determine which way the(New) gasket fits.   If you flip over your valve cover, you'll notice that there.is a noticeable difference in the 2&3.plug hole.cutouts.  one big, one slightly smaller.
Dry fit your gasket and pen mark the UP side so when you set it on the head, you'll know it's on right.
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"
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