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Author Topic: 1972 Honda CB750 K2 Crushwasher Question  (Read 655 times)

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Offline BikerBrains

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1972 Honda CB750 K2 Crushwasher Question
« on: May 11, 2025, 06:35:16 PM »
On my oil plug there is no crush washer. You know, the bottom plug that you remove to drain the oll.

After sitting for a few months, i noticed a leak from there. Anyone have any idea what size crush washer fits?
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Offline newday777

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Re: 1972 Honda CB750 K2 Crushwasher Question
« Reply #1 on: May 11, 2025, 07:51:31 PM »
12mm

#12
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 1 K2, 4 K6, 1 K8, 1 F1, 1 F3
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Online Don R

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Re: 1972 Honda CB750 K2 Crushwasher Question
« Reply #2 on: May 11, 2025, 08:44:26 PM »
 If you aren't ready to change the oil you could twist some teflon tape into a string, back the plug out a little and wind some into the gap, then re-tighten. Put on the crush washer next time.
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Offline bryanj

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Re: 1972 Honda CB750 K2 Crushwasher Question
« Reply #3 on: May 11, 2025, 11:58:49 PM »
Are you sure its not there? After multiple uses they get to look like part of the bolt!
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Offline newday777

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Re: 1972 Honda CB750 K2 Crushwasher Question
« Reply #4 on: May 12, 2025, 12:44:47 AM »
Quote from: bryanj on May 11, 2025, 11:58:49 PM
Are you sure its not there? After multiple uses they get to look like part of the bolt!
^^
Yes it can be mushroomed down around the head of the bolt
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 1 K2, 4 K6, 1 K8, 1 F1, 1 F3
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline Deltarider

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Re: 1972 Honda CB750 K2 Crushwasher Question
« Reply #5 on: May 12, 2025, 02:11:51 AM »
You can (re)use a crushwasher from a sparkplug.
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Offline beemerbum

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Re: 1972 Honda CB750 K2 Crushwasher Question
« Reply #6 on: May 12, 2025, 03:15:40 PM »
I went through a frustrating process with leaks from the drain plug area. Several different crush washers were used including genuine Honda units with leaks, albeit small persisting. Using baby powder, I discovered a crack in the pan adjoining the plug. It became clear that at some time in the past overzealous reefing on the plug caused the crack. Could even have been my own doing. A new (used) pan from eBay solved the problem. Bike is CB 750K2


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Offline BikerBrains

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Re: 1972 Honda CB750 K2 Crushwasher Question
« Reply #7 on: May 12, 2025, 05:57:40 PM »
Quote from: bryanj on May 11, 2025, 11:58:49 PM
Are you sure its not there? After multiple uses they get to look like part of the bolt!


its loooong gone, for sure.
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Offline BikerBrains

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Re: 1972 Honda CB750 K2 Crushwasher Question
« Reply #8 on: May 12, 2025, 05:58:07 PM »
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Offline BikerBrains

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Re: 1972 Honda CB750 K2 Crushwasher Question
« Reply #9 on: May 12, 2025, 05:59:30 PM »
Quote from: beemerbum on May 12, 2025, 03:15:40 PM
I went through a frustrating process with leaks from the drain plug area. Several different crush washers were used including genuine Honda units with leaks, albeit small persisting. Using baby powder, I discovered a crack in the pan adjoining the plug. It became clear that at some time in the past overzealous reefing on the plug caused the crack. Could even have been my own doing. A new (used) pan from eBay solved the problem. Bike is CB 750K2

I can see it leaking right where the plug goes it. Thankfully, there is no crack in the oil pan.
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