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Author Topic: cb750k oil leak  (Read 4109 times)

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Offline urbantiger

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cb750k oil leak
« on: April 18, 2011, 01:55:08 pm »
hi guys
im new to this forum..
my mate has just rebuilt the top half of his cb750k sohc motor..not sure of the year as he has it fitted into a chopper..
he fitted new base and head gaskets and rocker box gasket..
it now has an oil leak but not from the new gaskets..
the leak seems to be coming from above the head gasket and in between the 3rd and 4th exhaust outlet.if viewed from the front you can actually see right through to the back of the engine..i think there is a visible head stud in there..the leak is quite excessive...has he built the head up wrong?.maybe a washer or something missing from the head nut that tightens this stud down?.any ideas or do you need more information..
thanks
sean
ps i own a 1998 an 2007 cb1300 honda,s amongst others
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Offline Duke McDukiedook

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Re: cb750k oil leak
« Reply #1 on: April 18, 2011, 02:02:40 pm »
Leaky valve guide seals?
Year of model?

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"Well, Mr. Carpetbagger. We got somethin' in this territory called the Missouri boat ride."   Josey Wales

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CB750 K3 crat | (2) 1986 VFR750F

Offline urbantiger

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Re: cb750k oil leak
« Reply #2 on: April 18, 2011, 02:11:08 pm »
Quote from: Industrial-sized Dukiedook on April 18, 2011, 02:02:40 pm
Leaky valve guide seals?
Year of model?
not sure of the model the engine came out off...
dont think its valve stem seals as the oil its not burning oil or any oil visible in the exhaust outlets...the oil is dripping from the fins on front of engine like i said between the 2nd and 3rd finned exhaust collars...
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Offline urbantiger

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Re: cb750k oil leak
« Reply #3 on: April 18, 2011, 02:31:20 pm »
this is were the oil is coming from
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Offline fire113

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Re: cb750k oil leak
« Reply #4 on: April 18, 2011, 03:20:29 pm »
...may be one of the rubber seals under the cam tower isn't in the right position.

good luck...Georg
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Honda CB750 K0 & K0 & K1 & K1 & K2 & K2 & K6

Offline splitt

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Re: cb750k oil leak
« Reply #5 on: April 18, 2011, 06:54:24 pm »
+1 on the rubber cam tower nickels.
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Offline Magpie

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Re: cb750k oil leak
« Reply #6 on: April 18, 2011, 08:23:18 pm »
These black disks cover holes in the head, they are covered by the cam towers and if they aren't there you will have a good leak. Here they are. Cliff.
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Offline ekpent

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Re: cb750k oil leak
« Reply #7 on: April 18, 2011, 08:34:22 pm »
Guys are  correct on those black discs but notice also that your leak is close to the Tach drive outlet.That also has a gasket that has the potential to leak,might want to give it a quick check also.
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Offline jb750k1

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Re: cb750k oil leak
« Reply #8 on: May 29, 2011, 08:07:17 pm »
Would love to hear if you solve the problem. I have the same scenario, started my K1 bike today after top end rebuild and can't tell where the leak is but it's between 2 & 3 maybe near cam chain tunnel. It's not the head, valve cover or tach seal. Weird, heavy leak. Replaced pucks under cam towers.

Joe, Texas
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Offline urbantiger

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Re: cb750k oil leak
« Reply #9 on: May 31, 2011, 02:17:51 am »
hi guys..
sorry i havent been around..had connection problems..so changed my internet provider..

well ive cured the leak..took the cam cover off and removed camshafts etc and there was one of the little black rubber discs missing under the camshaft holders...
ordered new ones..just changed the 6 of them for him to be on the safe side..expensive little buggers...
checked tacho seal also..it was ok..bike runs fine now with no leaks at all..

ive almost finished restoring my 1977 honda cb400f..will le you all see some pics when its done..

thought id let you see some pics of the other bikes i have restored and own...
1976 suzuki rm125a
1978 yamaha rd250e
1980 yamaha dt250mx
1981 yamaha rd250lc
my current road bikes are a 1998 jap import cb1300sf and 2007 uk spec cb1300sa..
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Offline urbantiger

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Re: cb750k oil leak
« Reply #10 on: May 31, 2011, 02:19:54 am »
hi guys..
sorry i havent been around..had connection problems..so changed my internet provider..

well ive cured the leak..took the cam cover off and removed camshafts etc and there was one of the little black rubber discs missing under the camshaft holders...
ordered new ones..just changed the 6 of them for him to be on the safe side..expensive little buggers...
checked tacho seal also..it was ok..bike runs fine now with no leaks at all..

ive almost finished restoring my 1977 honda cb400f..will le you all see some pics when its done..

thought id let you see some pics of the other bikes i have restored and own...
1976 suzuki rm125a
1978 yamaha rd250e
1980 yamaha dt250mx
1981 yamaha rd250lc
my current road bikes are a 1998 jap import cb1300sf and 2007 uk spec cb1300sa..
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Offline ekpent

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Re: cb750k oil leak
« Reply #11 on: May 31, 2011, 04:21:26 am »
Thats an impressive, clean and diverse stash of machines you got there---Nice----
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Offline jb750k1

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Re: cb750k oil leak
« Reply #12 on: August 17, 2011, 08:54:45 pm »
Got a'71 750 that idles well, strong on wide open throttle but "flutters" at steady highway speed. Feel like a cylinder is just not on the money. Is this a carb sync issue?
Thx, Joe-Texas
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