Author Topic: I found the oil leak....CRAP!  (Read 2481 times)

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Offline Hotwheelbill

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I found the oil leak....CRAP!
« on: November 13, 2016, 12:36:25 PM »
Last project purchase a few months ago. 1975 CB750 that I thought I picked up cheap with a transmission problem. I had a little extra time today and pulled the chain guard cover. I think I found my problem to both the oil leak and transmission problem.
I love to make my bikes worthless due to high mileage!
2004 ST1300A .... the fast one. And dragging pegs on a CT.
1972…parts bike
1974…. Rusty frame but runs
1974 CB750..... Powder coated frame and parts, waiting for $$ hot rod motor.
1972 with 1975 old school drag motor

Offline calj737

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Re: I found the oil leak....CRAP!
« Reply #1 on: November 13, 2016, 12:51:36 PM »
Some see a problem, some see an opportunity.  ;)
'74 550 Build http://forums.sohc4.net/index.php?topic=126401.0
'73 500 Build http://forums.sohc4.net/index.php?topic=132935.0

"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline Hotwheelbill

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Re: I found the oil leak....CRAP!
« Reply #2 on: November 13, 2016, 01:45:26 PM »
Thank you for that. But I have my other 1976 CB 750 GSXR conversion that I have been working on. I was going to let this once it until I can get to it but I don't think this is something I want to conquer. So it will be on the for sale and/or Parts section sometime in the very near future.
I love to make my bikes worthless due to high mileage!
2004 ST1300A .... the fast one. And dragging pegs on a CT.
1972…parts bike
1974…. Rusty frame but runs
1974 CB750..... Powder coated frame and parts, waiting for $$ hot rod motor.
1972 with 1975 old school drag motor

Offline 754

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Re: I found the oil leak....CRAP!
« Reply #3 on: November 13, 2016, 01:57:02 PM »
 It can be done in a few days,if you get another set of cases and gaskets.
 Those can probably be fixed... I can cut out pieces if you are missing them..
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline ekpent

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Re: I found the oil leak....CRAP!
« Reply #4 on: November 13, 2016, 03:13:05 PM »
For others looking at a purchase in the future its a good idea to check that area out. Two screws and an impact can save some heartache down the road.
« Last Edit: November 14, 2016, 05:29:35 AM by ekpent »

Offline markreimer

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Re: I found the oil leak....CRAP!
« Reply #5 on: November 13, 2016, 06:57:09 PM »
My 74 750K had a hole in the same place. A thin patch was welded over. That was before I bought it, and about 25,000 miles ago at least. Fairly common injury I think. 


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Offline PeWe

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Re: I found the oil leak....CRAP!
« Reply #6 on: November 13, 2016, 10:43:26 PM »
First area to inspect when buing a CB750, bike or engine only. If the bike has been driven like that, check for sand inside. Pull engine and clean it.

I have read about guys patching it with JB weld. A good alu weld is a better start, though. Or find a new set of cases. Check the letters at front and you'll might find same letters so you can have same crank/bearings if good. I got an extra K2 cases with same as my K6, BBBBB.
« Last Edit: November 14, 2016, 03:00:30 AM by PeWe »
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline 754

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Re: I found the oil leak....CRAP!
« Reply #7 on: November 13, 2016, 11:00:09 PM »
Once you weld up and fix your first set of cases, you can truly run wide open without worrying...well maybe not Biily B..but most of us..
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline lrutt

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Re: I found the oil leak....CRAP!
« Reply #8 on: November 14, 2016, 05:10:59 AM »
looks like a job for a thin sheet of metal and JB unless the rest of the motor needs a refresh.
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 Don R

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Re: I found the oil leak....CRAP!
« Reply #9 on: November 14, 2016, 11:06:17 AM »
 A trans problem requires engine removal most of the time anyway, There is surely a cheap case or engine somewhere near you.
No matter how many times you paint over a shadow, it's still there.
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Offline Duanob

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Re: I found the oil leak....CRAP!
« Reply #10 on: November 14, 2016, 11:27:36 AM »
I think I'd just look for a decent used motor. With hole like that who knows if the engine was run without enough oil, there will be other problems like worn bearings, cam journals, etc. It will probably need an entire rebuild with bad cases. But that's just me.
"Just because you flush a boatload of money down the toilet, doesn't make the toilet worth more",  My Stepfather the Unknown Poet

1974 CB360T
1976 CB550K2 Resurrected
1976 CB550F2 Barn Find
1979 CX500 VG "HONDA-GUZZI"
2007 Moto Guzzi Breva 750ie
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Offline markreimer

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Re: I found the oil leak....CRAP!
« Reply #11 on: November 14, 2016, 12:06:00 PM »
Here's a photo of my 'discovered' repair. My chain was eating into the patch from the looks of it, I think when the tension wasn't set properly. Thankfully I discovered this shortly after I bought the bike (I could hear the chain hitting the case), which taught me to make sure the chain tension was right all the time. Never had a problem since then. I don't know if this case was split to do the repair as I've never been inside the bottom end, but it sure doesn't look like it was.

Offline 754

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Re: I found the oil leak....CRAP!
« Reply #12 on: November 14, 2016, 12:31:18 PM »
The best motor to do your firsr rebuild on, is one where you got nothing to lose.
Even buying a parts motor, and reassembling everything, with a bit of freshening up, is a tremendous learning experience .
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline markreimer

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Re: I found the oil leak....CRAP!
« Reply #13 on: November 14, 2016, 12:40:53 PM »
The best motor to do your firsr rebuild on, is one where you got nothing to lose.
Even buying a parts motor, and reassembling everything, with a bit of freshening up, is a tremendous learning experience .

This!! I second that entirely. I know SO much more about my 750 after doing a top-end build. And now I've got a complete parts engine that I'm going to use for a 'trail' bottom end job.

Offline Hotwheelbill

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Re: I found the oil leak....CRAP!
« Reply #14 on: November 14, 2016, 09:53:00 PM »
When I bought it, it would not go past 3rd gear, it would just to into neutral after third. From what I have read, it will need a tear down. As you can see, the bike has not been maintained very well, but it does run OK. The air shocks out back are odd, but I kind of like them. But the bike is complete and titled.
I may drop the pan and take a look. Not above JB Weld! It has saved my ass many times before.
I love to make my bikes worthless due to high mileage!
2004 ST1300A .... the fast one. And dragging pegs on a CT.
1972…parts bike
1974…. Rusty frame but runs
1974 CB750..... Powder coated frame and parts, waiting for $$ hot rod motor.
1972 with 1975 old school drag motor

Offline Stev-o

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Re: I found the oil leak....CRAP!
« Reply #15 on: November 14, 2016, 10:04:59 PM »
I think I'd just look for a decent used motor. With hole like that who knows if the engine was run without enough oil, there will be other problems like worn bearings, cam journals, etc. It will probably need an entire rebuild with bad cases. But that's just me.

Not just you, Duanob.  A spare motor could be swapped out in a few hours...
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline Hotwheelbill

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Re: I found the oil leak....CRAP!
« Reply #16 on: November 16, 2016, 12:35:06 PM »
I don't see me or anyone else patching or rebuilding this engine case. Take a look behind the sprocket.
I love to make my bikes worthless due to high mileage!
2004 ST1300A .... the fast one. And dragging pegs on a CT.
1972…parts bike
1974…. Rusty frame but runs
1974 CB750..... Powder coated frame and parts, waiting for $$ hot rod motor.
1972 with 1975 old school drag motor

Offline markreimer

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Re: I found the oil leak....CRAP!
« Reply #17 on: November 16, 2016, 12:39:19 PM »
I wouldn't write the case off so quickly personally. You can see my case pictured above had an equal size hole punched clean through the case, transmission exposed just like yours. Can be done.

..Of course, it might be easier to find a donor engine to drop in. That's what I did this summer when I cracked my main oil galley on the case and didn't want the hassle of splitting the cases to weld it back together.  ::)

Offline Hotwheelbill

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Re: I found the oil leak....CRAP!
« Reply #18 on: November 16, 2016, 01:55:19 PM »
I wouldn't write the case off so quickly personally. You can see my case pictured above had an equal size hole punched clean through the case, transmission exposed just like yours. Can be done.

..Of course, it might be easier to find a donor engine to drop in. That's what I did this summer when I cracked my main oil galley on the case and didn't want the hassle of splitting the cases to weld it back together.  ::)

But what is behind the sprocket is a crack in the lower engine case as well. I suspect it goes down to the sprocket shaft but I will not know until I pull that off. So this involves the upper and lower cases.
I love to make my bikes worthless due to high mileage!
2004 ST1300A .... the fast one. And dragging pegs on a CT.
1972…parts bike
1974…. Rusty frame but runs
1974 CB750..... Powder coated frame and parts, waiting for $$ hot rod motor.
1972 with 1975 old school drag motor

Offline markreimer

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Re: I found the oil leak....CRAP!
« Reply #19 on: November 16, 2016, 02:02:52 PM »
Oh! I didn't notice that, ah...not so simple then. Bummer dude.

Offline calj737

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Re: I found the oil leak....CRAP!
« Reply #20 on: November 16, 2016, 02:47:29 PM »
Upper and lower cases are matched, so ditch one and you buy a whole set. I think that area behind the sprocket will buff out  ;) ;D

Bill Benton in Alpharetta, GA probably has cases or a spare motor if you're seeking.
'74 550 Build http://forums.sohc4.net/index.php?topic=126401.0
'73 500 Build http://forums.sohc4.net/index.php?topic=132935.0

"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline 754

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Re: I found the oil leak....CRAP!
« Reply #21 on: November 16, 2016, 05:12:11 PM »
Often its both cases, if only one that a bonus, much easier cheaper, and easier to get it flat.
Easier if you have the chunks.... If not , I have one i could cut.

Often they are fixed for sentimental reasons or to keep correct cases in the bike.
To some it matter, others not. If you live in a registered by motor state, big incentive to fix.
 
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way