Author Topic: What is this hole in rear case of cb350f  (Read 317 times)

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Offline niem9

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What is this hole in rear case of cb350f
« on: November 06, 2018, 03:17:59 pm »
Hello all,

I have began doing a rebuild on a very rough cb350f (paid270$) when I removed the motor I discovered a hole that looked to be chipped Or busted out and there is scratch marks on the outside around it. Not sure what it’s from or why it’s there or if anyone has seen something like this... it is located on the Kickstarter side.. the motor turns over with good compression in wondering if I should epoxy weld it or have it welded professionally. Any input would be nice. Thanks.




Offline camshaft1991

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Re: What is this hole in rear case of cb350f
« Reply #1 on: November 06, 2018, 03:28:25 pm »
Is that something lodged into your case? Does it leak any oil?


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Offline niem9

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Re: What is this hole in rear case of cb350f
« Reply #2 on: November 06, 2018, 03:32:37 pm »
Nothing lodged that I can tell.. I’ll take the clutch cover off here shortly. And when I was kicking the motor it never leaked. I never got it running before the tear down so no telling there..

Offline camshaft1991

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Re: What is this hole in rear case of cb350f
« Reply #3 on: November 06, 2018, 03:34:37 pm »
If it’s a foreign metal object lodged in there you could see if you can take a magnet to it. Not to remove it but to see if there is something that is not aluminum


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Offline jaytee-nz

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Re: What is this hole in rear case of cb350f
« Reply #4 on: November 06, 2018, 04:19:22 pm »
Based on the shape of the hole, it looks like something has hit the case from inside the engine causing it to burst out. I would definitely look inside the engine to check if something has let go.

Offline PeWe

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Re: What is this hole in rear case of cb350f
« Reply #5 on: November 06, 2018, 09:05:33 pm »
Bullet hole, lead encapsulated in case?
Or someone has used a too long bolt.
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Offline 754

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Re: What is this hole in rear case of cb350f
« Reply #6 on: November 06, 2018, 10:05:11 pm »
Try turning it over with kicker, while watching the hole.
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Offline strynboen

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Re: What is this hole in rear case of cb350f
« Reply #7 on: November 07, 2018, 04:34:36 am »
its a "inside aut hole"..think somthing in the kickstart mekanism..is inthere..so thek the books for split draving for that areia..or thek cms.nl..there you can see all parts...

but best to split the case..and thek for broken parts ..and get it tig weldet..
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Offline niem9

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Re: What is this hole in rear case of cb350f
« Reply #8 on: November 07, 2018, 04:46:06 am »
Thanks all for the reply’s. I removed the clutch cover and found that the hole is inline with the kick start mechanism, just missed the gears and is exposing the rounded surface of the mechanism. Seems the be the best of a worse case situation. I didn’t find any metal in the clutch case. I thought the hole could of been a place where a breather nipple of some sorts could have been and sheared off but doesn’t seem like it.

In the picture I have a screw driver going through the hole, it barey fit as the hole looks larger in the pictures than it actually is.


Offline Don R

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Re: What is this hole in rear case of cb350f
« Reply #9 on: November 07, 2018, 06:04:45 am »
 Hopefully there isn't a piece of loose metal in the motor. If you aren't concerned with appearance you could drill it and tap for a pipe plug. I'd weld it.
If the things you own end up owning you, it's better to be owned by some cool things.

Offline niem9

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Re: What is this hole in rear case of cb350f
« Reply #10 on: November 07, 2018, 06:42:38 am »
I believe it would of had to go through the oil pump screen to get into the motor so hopefully that stopped any further damage.

Offline 540nova

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Re: What is this hole in rear case of cb350f
« Reply #11 on: November 07, 2018, 07:16:05 am »
Obviously welding it up is the preferred fix, but JB Weld is a quick permanent fix, as well.
I'd thoroughly degrease with acetone,  apply tape on the inside as a temporary backer, and lay JB in the hole, smoothing it out with a spatula. To some that may sound "shade-tree", but it just plain works.  'Nuff said.

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Offline Don R

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Re: What is this hole in rear case of cb350f
« Reply #12 on: November 07, 2018, 12:46:30 pm »
I believe it would of had to go through the oil pump screen to get into the motor so hopefully that stopped any further damage.

A bolt, nut or other chunk of metal in an engine may act like a bullet in there. A 1/4 X 1/2" long bolt cost me $3K a couple years ago zinging around in my race car's engine. It fell from the valvetrain, got into the crankcase and dinged up a set of 565" pistons, one cylinder bottom and a sweet set of Manley H beam rods.  It even made knuckle bumps in the pan.
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Offline Tracksnblades1

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Re: What is this hole in rear case of cb350f
« Reply #13 on: November 07, 2018, 12:57:03 pm »
I believe it would of had to go through the oil pump screen to get into the motor so hopefully that stopped any further damage.

A bolt, nut or other chunk of metal in an engine may act like a bullet in there. A 1/4 X 1/2" long bolt cost me $3K a couple years ago zinging around in my race car's engine. It fell from the valvetrain, got into the crankcase and dinged up a set of 565" pistons, one cylinder bottom and a sweet set of Manley H beam rods.  It even made knuckle bumps in the pan.

+1 .. I found a aircleaner wing nut that went through the cylinder wall after it ran out of room when the 302 Ford piston went to TDC. Nobody knew how it got there either.

Don R has more toys than I do. Sound like you have some good 565 man cave decorations.
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