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Author Topic: How to check if the oil check valve is stuck CB750  (Read 1254 times)

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Offline Turbogrimace

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How to check if the oil check valve is stuck CB750
« on: August 14, 2009, 05:58:20 AM »
My oil light wont go out and I'm not sure why.  When the engine is running, how much oil should be in the pan?  I popped the drain plug while the engine was running to see how much would flow out, but I only got a very small spray.  Oil is flowing back up to the tank too.  Im just not sure if it's flowing back down.  Any thoughts?

Offline MCRider

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Re: How to check if the oil check valve is stuck CB750
« Reply #1 on: August 14, 2009, 06:45:12 AM »
My oil light wont go out and I'm not sure why.  When the engine is running, how much oil should be in the pan?  I popped the drain plug while the engine was running to see how much would flow out, but I only got a very small spray.  Oil is flowing back up to the tank too.  Im just not sure if it's flowing back down.  Any thoughts?

Not much to offer, I just wanted to be notified of posts to your thread.

At any time, running or no, there won't be much oil in the pan. The pump should be pickig it up about as fast as it gets there... I think.

The #1 reason for the oil light staying on is a bad oil light switch. Happened to me. Nevertheless, you have to check it out.  If you had a buddy you could swap switches with you'd know. Easy to change out.
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Youth and Talent are no match for Age and Treachery.

Offline Turbogrimace

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Re: How to check if the oil check valve is stuck CB750
« Reply #2 on: August 14, 2009, 07:38:50 AM »
Easy to change out if the mag wasnt in the way.  I'll try and pop it out. I have another one sitting on the shelf.  Not sure if that one works though haha.

And what is this notification of posts that you are talking about?  Ohhh Son of a basketweaver.  I never noticed the Additional Options.  Well isnt that nice.

Offline MCRider

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Re: How to check if the oil check valve is stuck CB750
« Reply #3 on: August 14, 2009, 07:43:47 AM »
Easy to change out if the mag wasnt in the way.  I'll try and pop it out. I have another one sitting on the shelf.  Not sure if that one works though haha.

And what is this notification of posts that you are talking about?  Ohhh Son of a basketweaver.  I never noticed the Additional Options.  Well isnt that nice.
In addition to the "Additional Options" checkbox, the threads in which I (you) have participated will show up when the link "Show new replies to your posts" is clicked at the top of the page. Gives me a quick list of threads in which I have an interest and to which a new post has been added.

Actually i'm not sure how the Addtl Options checkbox works. I think it throws a notice into your email box, which I don't really want. It may throw a notice into the Forums Messages inbox, I don't know.

Hope your second switch works. Otherwise...
« Last Edit: August 14, 2009, 07:47:41 AM by MCRider »
Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
Youth and Talent are no match for Age and Treachery.

Offline mystic_1

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Re: How to check if the oil check valve is stuck CB750
« Reply #4 on: August 14, 2009, 09:05:24 AM »
Got an oil pressure gauge you can toss on there as a diagnostic?  If your magneto interferes with the pressure switch you may not have room at the gallery access plug for a gauge though...

mystic_1
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Offline Turbogrimace

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Re: How to check if the oil check valve is stuck CB750
« Reply #5 on: August 14, 2009, 09:42:30 AM »
No room at the galley plug. 

Offline mystic_1

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Re: How to check if the oil check valve is stuck CB750
« Reply #6 on: August 14, 2009, 09:48:21 AM »
You could always drop the sump pan and yank the pump for direct inspection.

mystic_1
"When you are wrestling for possession of a sword, the man with the handle always wins. "  - Neal Stephenson, Snow Crash

My build thread:  http://forums.sohc4.net/index.php?topic=68952.0


Offline Turbogrimace

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Re: How to check if the oil check valve is stuck CB750
« Reply #7 on: August 14, 2009, 09:51:28 AM »
Thats what I'm thinking of doing.

I have to remove the pan anyways. The plug stripped the threads out of the pan.  It's been like that since I got the engine out of the dirt.  There's another question.  Can the pan be retapped and put a larger bolt in or what's a good way to fix that.

Offline mystic_1

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Re: How to check if the oil check valve is stuck CB750
« Reply #8 on: August 14, 2009, 09:59:41 AM »
I think there's sufficient meat there to tap if you have a tap that size.  That said, sump pans are cheap on feeBay.

I know they make oversized, self-tapping plugs for cars, never looked into one for a 750 though.


mystic_1
"When you are wrestling for possession of a sword, the man with the handle always wins. "  - Neal Stephenson, Snow Crash

My build thread:  http://forums.sohc4.net/index.php?topic=68952.0


Offline Turbogrimace

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Re: How to check if the oil check valve is stuck CB750
« Reply #9 on: August 14, 2009, 11:18:33 AM »
Hmm, self tapping aye!

I wanted the finned F model pan and they are harder to find.  I have a pile of other pans here.  I'll look for a self tapper.  Although once you thread that in, wont there be metal shavings floating about?

Offline mystic_1

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Re: How to check if the oil check valve is stuck CB750
« Reply #10 on: August 14, 2009, 01:49:04 PM »
I've wondered that myself.  Never used one, just seen them in the aisles at the local auto parts store.

mystic_1
"When you are wrestling for possession of a sword, the man with the handle always wins. "  - Neal Stephenson, Snow Crash

My build thread:  http://forums.sohc4.net/index.php?topic=68952.0


Offline Turbogrimace

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Re: How to check if the oil check valve is stuck CB750
« Reply #11 on: August 16, 2009, 06:14:56 PM »
Well I dropped the pan, and pulled the oil pump apart.  Everything checks out, minus a little leakage on the oil stopper.  No biggie there, just makes changing the oil easier.  I guess it's gotta be the oil pressure switch.

As for the pan, I retapped the threads to accept the all too common MP 12 drain plug. It's 1/2-20 threads.  Took 30 seconds and works like a charm. 

I'll get to the oil switch in a little bit.  Right now Im trying to figure out why my throttle is sticking up in the electrics housing (harley stuff pshhhh).

 

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