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Author Topic: From bad to worse - CB750K4 engine rebuild  (Read 1426 times)

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Offline andy750

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From bad to worse - CB750K4 engine rebuild
« on: May 19, 2006, 11:09:51 AM »
As some of you may remember I had an oil leak coming from bewteen the upper fins at the front of my CB750K4. It didnt look as though it was coming from the head gasket and so I guessed it was the oil seals under the cam towers were needing replaced. I pulled the engine, put in the new ol seals under the cam towers and added a new cam cover gasket...reassembled and the bike fired up with the new Mac 4-2 exhaust...this was Sunday....last night I took it for its first spin and it ran and sounded very good....however when I stopped to inspect the head at the front there was oil literally pouring out from between #2 and #3 pipes....inbetween the fins!!!! So I road the short distance home with no problem apart from some smoke coming from the front and the oil now flooding out!!

Does anyone have ANY ideas how this could happen?? In the past Ive repaced the valve oil seals, the head gasket and now the oil seals under the cam towers....so Im at a loss of where exactly this oil could be coming from now....from being a spot coming out it now is a flood :-(......lucky I have another K4 to rde..

Thanks in advance,
Andy in Boston
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Current bikes
1. CB750K4: Long distance bike, 17 countries and counting...2001 - Trans-USA-Mexico, 2003 - European Tour, 2004 - SOHC Easy Rider Trip , 2008 - Adirondack Tour 2-up , 2013 - Tail of the Dragon Tour , 2017: 836 kit install and bottom end rebuild. And rebirth: http://forums.sohc4.net/index.php/topic,173213.msg2029836.html#msg2029836
2. CB750/810cc K2  - road racer with JMR worked head 71 hp
3. Yamaha Tenere T700 2022

Where did you go on your bike today? - http://forums.sohc4.net/index.php?topic=45183.2350

Offline Hondell

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Re: From bad to worse - CB750K4 engine rebuild
« Reply #1 on: May 19, 2006, 11:20:51 AM »
Hi Andy:

I've seen # 2 and 3 leak due to the cam chamber wall being perforated by a rattling cam chain.

Rick
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1972 Cb750 resto- 1972 Cb750 stoplight racer- 1972 Cb750 vintage touring - 1979 CBX- 1982 Kaw GPZ- 1968 Honda SS125A

Offline Clutch Cargo

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Re: From bad to worse - CB750K4 engine rebuild
« Reply #2 on: May 19, 2006, 02:09:48 PM »
I know that sickening feeling - too much time and money spent on parts and new gaskets - only to have an oil leak.

ARRRGGGG.....

Is the oil clear, or is it discolored  - say from the exhasust?

MIke


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1976  CB750K6
1976 GL1000
1994 - ST1100
1985 - HRS21

Offline andy750

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Re: From bad to worse - CB750K4 engine rebuild
« Reply #3 on: May 19, 2006, 02:15:01 PM »
The oil is clear (as it was freshly out in on Sunday :-() and is coming from the upper fins between #2 and #2 exhaust....literally gushing out from the hole between the plugs (I think) - will check more tonite.....

cheers
Andy
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Current bikes
1. CB750K4: Long distance bike, 17 countries and counting...2001 - Trans-USA-Mexico, 2003 - European Tour, 2004 - SOHC Easy Rider Trip , 2008 - Adirondack Tour 2-up , 2013 - Tail of the Dragon Tour , 2017: 836 kit install and bottom end rebuild. And rebirth: http://forums.sohc4.net/index.php/topic,173213.msg2029836.html#msg2029836
2. CB750/810cc K2  - road racer with JMR worked head 71 hp
3. Yamaha Tenere T700 2022

Where did you go on your bike today? - http://forums.sohc4.net/index.php?topic=45183.2350

Offline lrutt

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Re: From bad to worse - CB750K4 engine rebuild
« Reply #4 on: May 19, 2006, 02:42:49 PM »
ditto the hole in the head from the cam chain.
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06 Harley Sporster 1200C, 06 Triumph Scrambler, 01 Ducati Chromo 900, 01 Honda XR650L, 94 Harley Heritage, 88 Honda Hawk GT, 84 Yamaha Virago 1000, 78 Honda 750K w/sidecar, 77 Moto Guzzi Lemans 850, 76 Honda CB750K, 73 Norton 850, 73 Honda Z50, 70 & 65 Honda Trail 90, 70 & 71 Triumph 650s, 65 Honda 305 Dream, 81 Honda 70 Passport, 70 Suzuki T250II, 71 Yamaha 360 RT1B, 77 BMW R75/7, 75 Honda CB550K, 70 Honda CT70

Offline andy750

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Re: From bad to worse - CB750K4 engine rebuild
« Reply #5 on: May 19, 2006, 02:44:48 PM »
Is there a repair for the perforated wall/hole in the head? if that is the case....and how would I check this option?

thanks
Andy
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Current bikes
1. CB750K4: Long distance bike, 17 countries and counting...2001 - Trans-USA-Mexico, 2003 - European Tour, 2004 - SOHC Easy Rider Trip , 2008 - Adirondack Tour 2-up , 2013 - Tail of the Dragon Tour , 2017: 836 kit install and bottom end rebuild. And rebirth: http://forums.sohc4.net/index.php/topic,173213.msg2029836.html#msg2029836
2. CB750/810cc K2  - road racer with JMR worked head 71 hp
3. Yamaha Tenere T700 2022

Where did you go on your bike today? - http://forums.sohc4.net/index.php?topic=45183.2350

Offline mcpuffett

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Re: From bad to worse - CB750K4 engine rebuild
« Reply #6 on: May 19, 2006, 03:31:10 PM »
may sound stupid but could you have missed putting a fastner back in?  mick.
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Honda CB750 KO 1970,   Honda VTX 1300 2006, Lancaster England.

Offline scondon

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Re: From bad to worse - CB750K4 engine rebuild
« Reply #7 on: May 19, 2006, 04:08:57 PM »
Quote from: andy750 on May 19, 2006, 02:15:01 PM
....literally gushing out from the hole between the plugs

  Hole? What hole?

Quote from: mcpuffett on May 19, 2006, 03:31:10 PM
may sound stupid but could you have missed putting a fastner back in?  mick.

   Maybe?
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Re: From bad to worse - CB750K4 engine rebuild
« Reply #8 on: May 19, 2006, 05:43:17 PM »
Any chance its coming from the cylinder head cover gasket?  Not the cam-towers/cam-cover?  Hope it gets sorted...
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