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Author Topic: Drilling frame drain holes - cb750  (Read 2643 times)

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Offline Prospect

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Drilling frame drain holes - cb750
« on: April 25, 2012, 05:56:42 PM »
Apparently some of the k1 frames didn't come with drain holes so I'm thinking of drilling my own.  The two holes are supposed to be ahead of the engine mounts near the dowtubes.  Any of you guys do this and can give me some pointers?  It's fairly straight forward but I don't want to drill in the wrong spot and have a lesser effect.  Also what's  a good product to spray in there to inhibit rust?

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Offline Don R

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Re: Drilling frame drain holes - cb750
« Reply #1 on: April 25, 2012, 08:42:40 PM »
I drilled back near the lower rear mounts, it seemed to be the low point at the time. I also welded a new left side tube on it, it was split from mount to mount, looked like it had been filled and frozen.
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Offline lucky

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Re: Drilling frame drain holes - cb750
« Reply #2 on: April 25, 2012, 09:15:16 PM »
Quote from: Prospect on April 25, 2012, 05:56:42 PM
Apparently some of the k1 frames didn't come with drain holes so I'm thinking of drilling my own.  The two holes are supposed to be ahead of the engine mounts near the dowtubes.  Any of you guys do this and can give me some pointers?  It's fairly straight forward but I don't want to drill in the wrong spot and have a lesser effect.  Also what's  a good product to spray in there to inhibit rust?

It is not needed. If the tube is sealed up then no air can get inside the tube and it will not rust. I am a welder and have cut many tubes open and the ones that are sealed are not corroded inside. If water can get in the tube, then  a drain hole WOULD be needed.
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Offline Don R

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Re: Drilling frame drain holes - cb750
« Reply #3 on: April 25, 2012, 09:19:08 PM »
That's the problem with the K0 and K1, it was a factory bulletin to the dealers but most didn't do it. These things have several places water can enter. I like my bike clean but I guess I should avoid a pressure washer.
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Offline MoMo

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Re: Drilling frame drain holes - cb750
« Reply #4 on: April 25, 2012, 09:39:26 PM »
Here are some photos of potential damage...Larry

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Offline Don R

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Re: Drilling frame drain holes - cb750
« Reply #5 on: April 25, 2012, 10:17:01 PM »
Wow that's as bad as mine was.
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Offline HondaMan

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Re: Drilling frame drain holes - cb750
« Reply #6 on: April 25, 2012, 10:20:44 PM »
Quote from: Prospect on April 25, 2012, 05:56:42 PM
Apparently some of the k1 frames didn't come with drain holes so I'm thinking of drilling my own.  The two holes are supposed to be ahead of the engine mounts near the dowtubes.  Any of you guys do this and can give me some pointers?  It's fairly straight forward but I don't want to drill in the wrong spot and have a lesser effect.  Also what's  a good product to spray in there to inhibit rust?



The holes should be 7/32" to 1/8" size, just behind the forward motor mounts. Use CRC spray, or regular motor oil. Avoid WD40, it is made to ATTRACT water, and does it well!
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Offline mycb750k6

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Re: Drilling frame drain holes - cb750
« Reply #7 on: April 26, 2012, 06:14:25 AM »
I drilled an early CB750 K1 frame that was missing drain holes and when I did, water came out - quite a bit of it.
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Offline zzpete

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Re: Drilling frame drain holes - cb750
« Reply #8 on: April 26, 2012, 11:28:10 AM »
Quote from: mycb750k6 on April 26, 2012, 06:14:25 AM
I drilled an early CB750 K1 frame that was missing drain holes and when I did, water came out - quite a bit of it.
Wow!! I guess I should do mine!!!
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Offline lucky

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Re: Drilling frame drain holes - cb750
« Reply #9 on: April 26, 2012, 11:40:01 AM »
Quote from: mycb750k6 on April 26, 2012, 06:14:25 AM
I drilled an early CB750 K1 frame that was missing drain holes and when I did, water came out - quite a bit of it.

And if water got in - then air can get in=corrosion.
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