Question about oil pan and oil drain plug

[S_JH]

I've had a slow oil leak from the oil drain plug for some time. (My cycle is a 1982 CB750C.)

It began when I was tightening the oil drain plug at one point, and felt the threads give (or snap). After that point, the bolt would thread in and out, but never stop turning. I could thread it in until the bolt and washer were snug against the oil pan, but it would never tighten up and stop turning.

I found an oversized bolt with tapping-threads, and managed to get it in. But that oversized bolt has the same problem: it will thread in, but not tighten up.

To reduce oil drips, I would use some high-temp gasket sealant on the washer for the drain plug, and thread it in by hand until the gasket sealant would squish flat. It still left a few drops on the garage floor occasionally.

Now I'm trying to figure out if the threads can be repaired, or if I should go shopping for a replacement oil pan with better threads.

What do you guys think?

 

[dirtdigger]

could be cracked, just go on ebay and get a pan that isnt stripped

 

[Twobond]

Like that Idea. About a different oil pan
Walter

 

[S_JH]

Update: I ordered a replacement oil pan from an eBay seller.
Working on it today, I might be able to get the bike running this weekend.

 

[sergei]

maybe you can cut the thread to a size larger than the standard one.

 

[SenseAmidMadness]

maybe you can cut the thread to a size larger than the standard one.

The issue with jumping right into that is that the pan has reinforcement ribs built into the casting, adjacent to the drain bolt hole, that can't be seen from outside. If any of these are cracked then tapping the hole larger could widen the cracks.

I'd pull the pan regardless. Check whether overtightening the drain bolt made any cracks in the aluminum.


And to the original poster: buy a torque wrench. Even the old-school beam types are out there and cheap new ($30 or less). After you replace that pan, tightening that bolt to the factory spec and no more will prevent this from happening again.

 

[S_JH]

The issue with jumping right into that is that the pan has reinforcement ribs built into the casting, adjacent to the drain bolt hole, that can't be seen from outside. If any of these are cracked then tapping the hole larger could widen the cracks.

I'd pull the pan regardless. Check whether overtightening the drain bolt made any cracks in the aluminum.


And to the original poster: buy a torque wrench. Even the old-school beam types are out there and cheap new ($30 or less). After you replace that pan, tightening that bolt to the factory spec and no more will prevent this from happening again.

Thanks for confirming this, that simply cutting new threads might cause more problems than I wanted.

I definitely decided to pull the oil pan. I ended up going with a replacement oil pan, from eBay.... after I did some research, and looked at the oil pan that I had pulled, to make sure that shape was correct.

Now I have an interesting issue. The exhaust was much harder to put back on than it was to pull off, and I couldn't remember which way the little Exhaust Pipe Collars went on. So I did them one way, then discovered that I'd put them on wrong...and now I'm taking them off, and putting them back on the correct way.

But I didn't realize, until looking at the parts diagram, that there was a copper ring, called 'Exhaust Headpipe Gasket', that is supposed be be inside the hole that the exhaust pipe goes into.

I'm pretty sure the old Exhaust Headpipe Gasket is still in there... do you think I need to order new ones, or can I use the ones that are in there?

 

[Raggaren]

Use the once you got.
If you get exhaust leak there.
Then replace copper gasket

 

[SenseAmidMadness]

Thanks for confirming this, that simply cutting new threads might cause more problems than I wanted.

I definitely decided to pull the oil pan. I ended up going with a replacement oil pan, from eBay.... after I did some research, and looked at the oil pan that I had pulled, to make sure that shape was correct.

Now I have an interesting issue. The exhaust was much harder to put back on than it was to pull off, and I couldn't remember which way the little Exhaust Pipe Collars went on. So I did them one way, then discovered that I'd put them on wrong...and now I'm taking them off, and putting them back on the correct way.

But I didn't realize, until looking at the parts diagram, that there was a copper ring, called 'Exhaust Headpipe Gasket', that is supposed be be inside the hole that the exhaust pipe goes into.

I'm pretty sure the old Exhaust Headpipe Gasket is still in there... do you think I need to order new ones, or can I use the ones that are in there?

They're soft copper crush rings used as an exhaust gasket. Per the Honda manual they get replaced every time...but Raggaren is right. It's not a guarantee they will leak if you reuse them once.

Even if they don't hold a seal with reuse, they're cheap to replace ($3.42 each from VintageCB750), and you do not have to use genuine Honda parts which can make them even cheaper. Ebay/Amazon generics will work just as well if they're the right size.