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Author Topic: "Crack" in engine case  (Read 598 times)

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Offline theslayedsaint

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"Crack" in engine case
« on: October 01, 2014, 08:59:10 AM »
Hey guys,
So after months of buying parts I'm almost ready to put my CB750 back togther..
When I notice the wear in the bottom half of my case. Could you guys please tell me how bad this is? I'm hoping its just some bad wear from the gears. Any thoughts would be great!
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1974 CB750 custom build cafe racer
-849cc big bore
-Webcam 63a
-APE rods
-4-1 stainless exhaust
-GSXR front end

Offline lrutt

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Re: "Crack" in engine case
« Reply #1 on: October 01, 2014, 09:08:41 AM »
can't zoom in on the image.
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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 iron_worker

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Re: "Crack" in engine case
« Reply #2 on: October 01, 2014, 09:31:00 AM »
I don't see any cracks. Are you talking about the rub marks from the chain? If so, this probably just means it's time for a new primary chain or timing chain /tensioner (I can't tell where I'm really looking at in the case). That piece where the aluminum has flaked off in the surface is probably just a casting defect and I don't think it will affect the strength enough to be a concern.

*edit* I see now this is the final drive area so probably time for a new primary chain. *edit*

IW
« Last Edit: October 01, 2014, 09:33:40 AM by iron_worker »
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Offline 754

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Re: "Crack" in engine case
« Reply #3 on: October 01, 2014, 10:21:08 AM »
Looks like a bit of corrosion to me,unless you mean another area.
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Offline Don R

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Re: "Crack" in engine case
« Reply #4 on: October 01, 2014, 10:26:44 AM »
Maybe an arrow made with a sharpie pointing at it?
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: "Crack" in engine case
« Reply #5 on: October 01, 2014, 12:54:55 PM »
Casting boo boo. Nothing to worry about as long as what you are referring to is that little divot.
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As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline theslayedsaint

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Re: "Crack" in engine case
« Reply #6 on: October 01, 2014, 03:33:09 PM »
Yes sorry I didn't mean to say crack, it does look more like corrosion. Or some type of rubbing of the chain.The engine is getting overhauled and new chains, so sounds like I'll be ok. thanks for the fast replies.
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1974 CB750 custom build cafe racer
-849cc big bore
-Webcam 63a
-APE rods
-4-1 stainless exhaust
-GSXR front end
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