Topic: Will this work ok?...engine swap/oil tank issue

[seanbarney41]

I am going to use a 77-78k 750 engine with an early k oil tank.  I could use some advice about what to do with the oil tank vent lines.   What does the big hose connector on the back of the 77-78k transmission connect to?.  On the early bikes it connects to the little nipple on the oil tank and the big nipple is just a vent, right?  I am thinking of using the big nipple as a vent and finding some sort of hose size adapter for the connection on the back of the transmission.

[seanbarney41]

bump...still not sure about this, is that gonna work?  does anybody even know what I'm talking about?

[lucky]

The tank venting has to connect to the port(tube) on the back of the transmission.
Whatever it takes to do that.

That hose on the tank takes any oil that sloshes over, and just sends it right back to the engine via the transmission along with the gases.

The gases find their way to the top of the engine to the port/tube on the cylinder head. Then you can have a oil /gas vent separator on that tube as well.

[Gonzowerke]

I just had to run down to the garage to look at my "77 F, as it still has the oil tank and lines in place, unlike my '78K. On the F, there is a short length of large diameter hose that goes from the nipple on the back of the trans, to a nipple on the bottom of the tank, that is the same size as the trans one. It can't be a drain into the trans, so inside the tank there must be a tube that goes up above the oil level. The only other vents are on the engine and not the tank. There is a line that goes from the valve cover to an air/oil separator under the battery, and then a line from that to the airbox. On the bottom of the separator is a drain line that runs along the swingarm. I'm guessing the system sucks vapor from the tank through the engine, out the valve cover, and through the separator, where it then goes to the airbox to be burned. Here is a picture, showing only the bottom vent, there are no others for these years that I know of.
http://www.cmsnl.com/honda-cb750k8-four-usa_model14397/partslist/F14.html

[seanbarney41]

Gonzowerke, What's that other nipple in your parts diagram right above 18?...so the k7-8 oil tank only has one vent connection?...that goes to the back of the tranny?   Should I do as hypothesized in my first post and use a hose adapter to connect the small nipple on the early tank to the back of the tranny, and the larger nipple on the early tank vented below the swingarm?

[scottly]

Read this thread:
http://forums.sohc4.net/index.php?topic=95059.0

[Gonzowerke]

Gonzowerke, What's that other nipple in your parts diagram right above 18?...so the k7-8 oil tank only has one vent connection?...that goes to the back of the tranny?   Should I do as hypothesized in my first post and use a hose adapter to connect the small nipple on the early tank to the back of the tranny, and the larger nipple on the early tank vented below the swingarm?

That is the nipple I'm talking about. #25 and #26 are the seals for the oil hoses, with the attachment points for the hoses above them.
I have never seen an early tank, so i know nothing about them, but looking at the other thread, that Scottly pointed us to, I would just attach it to where the earlier engine's trans hose went, the lower, smaller nipple.

[seanbarney41]

Thanks for the link Scottly, I had actually already read that one in my search but it looks like the 77-78k engines have a different set up as there is no chain oiler and the nipple on the back of the tranny is larger sized than the small nipple on the early oil tank that usually connects there.  Does anybody  know if there is just one nipple on the 77-78k oil tank?  I am trying to use a 77-78k motor in an early frame and thus an early oil tank....

[seanbarney41]

Gonzowerke, What's that other nipple in your parts diagram right above 18?...so the k7-8 oil tank only has one vent connection?...that goes to the back of the tranny?   Should I do as hypothesized in my first post and use a hose adapter to connect the small nipple on the early tank to the back of the tranny, and the larger nipple on the early tank vented below the swingarm?

gotcha, so there is just one nipple besides the actual oil feed/return lines right?
That is the nipple I'm talking about. #25 and #26 are the seals for the oil hoses, with the attachment points for the hoses above them.
I have never seen an early tank, so i know nothing about them, but looking at the other thread, that Scottly pointed us to, I would just attach it to where the earlier engine's trans hose went, the lower, smaller nipple.