Topic: 1978 CB750K — Post 836 OIL PRESSURE - not good

[Restoration Fan]

Here you go.  I just went and took the picture on Stella...another 78K.

[SKTP]

Thank you! Mine is not in properly. And Thank you 754...I will get this bike leak free!!!!

[Restoration Fan]

Chris,
If it doesn't want to seat properly, try removing it and bumping the starter slightly so that it rotates the crank.  I can't describe it properly but when it goes in right, you'll know.  Because it will go in deeper than before.  </ends sexual reference>

Ron

[754]

The seal washers on the oil lines, you could probably use and reuse,  if you can find copper ones, Earls Supply may have, not sure how far that is for you. Someone in the City of Angels should have a set..

[Restoration Fan]

Yes, you can reuse the washers.  I re-used the ones on Stella and no leaks so far.  (Knock on wood)

[754]

Yes but once they leak,  they usually. Keep leaking.

[SKTP]

I'm honestly not sure if they are even in there? Waiting to get them to do my first oil change since re-build 2

[Tintop]

Places that sell metric nuts & bolts generally carry both copper & aluminium washers, and at less cost than buying from Honda.  I have always got mine from Brafasco here.

[SKTP]

There is a tach seal in my tach drive...it seems to be seated but I cannot get the cable to go all the way in...very confused

the tach cable end has "thread grooves" from the retainer screw holding it in, not all the way in I tried filing those off end, thinking it's no longer round...but it's still not going in

I check the depth everywhere and tried to push the seal back as far as possible...it make no sense why is not going in....

[RandyBMC]

Turn the engine a little while you are pushing it in and it may help the groves on each drive mesh.

[MCRider]

There is a tach seal in my tach drive...it seems to be seated but I cannot get the cable to go all the way in...very confused

the tach cable end has "thread grooves" from the retainer screw holding it in, not all the way in I tried filing those off end, thinking it's no longer round...but it's still not going in

I check the depth everywhere and tried to push the seal back as far as possible...it make no sense why is not going in....

Is the old seal still there? That would cause your problem, has happened before. Cable should be loosy goosy in the drive mound.

[SKTP]

I'll wait to pick it out once my new one gets here...it looks like picking it out is not going to be easy...but maybe it will just pop out if I'm lucky

New question...you know that metal vent tube that sticks out the back of the bottom cases pointing right at the swing arm...what is suppose to be attached to that? Could that be blowing oil all over my swingarm?

[MCRider]

I'll wait to pick it out once my new one gets here...it looks like picking it out is not going to be easy...but maybe it will just pop out if I'm lucky

New question...you know that metal vent tube that sticks out the back of the bottom cases pointing right at the swing arm...what is suppose to be attached to that? Could that be blowing oil all over my swingarm?

The generally accepted method for pulling that seal is to take a tiny drill bit and drill into it. then thread a tapered screw into the seal and pull it out.

The spigot on the rear of the tranny attaches to a port on the low inside side of the oil tank. Yes, if it is not attached you will oil your swingarm and eventually your tire. If you are already assembled, its a bit difficult to get to the teet on the oil tank. The battery box is in the way. You may need to remove the side cover, oil tank mount bolts and lean the tank out to get your hand in there.

[SKTP]

Oh!!!! Thanks I just have a hose on the oil tank ven running out the back...you are saying it should connect to the engine case....maybe that's been the issue all along...

Thank you MCRIDER! I will get this bike not leaking somehow!

[MCRider]

Oh!!!! Thanks I just have a hose on the oil tank ven running out the back...you are saying it should connect to the engine case....maybe that's been the issue all along...

Thank you MCRIDER! I will get this bike not leaking somehow!

Yes, back of the engine case hose connects to oil tank. Not the big vent hose up high. ITs a lower spigot on the tank, about a 12 inch or less length of hose. The spigot on the lower inside side of oil tank is actually a pipe that runs inside the tank up to the condenser bulb up high. Pressure from inside the engine is slightly relieved, and more importantly, condensed oil flows down the pipe, exits the oil tank, and rather than to the atmosphere or swing arm in this case, it continues into the back of the engine cases and onto the little tray that feeds it into the chain oiler. So essentially you're getting oil meant for the chain oiler onto your swing arm.

You will be much happier when the two nipples are hooked together. 

[SKTP]

I am pretty sure there's only one vent on my 78K oil tank...here's a picture I grabbed off ebay

I plan on connecting that to the engine vent. I know there's a bunch of tubes for the emmission standards on the 78K but mine are all gross and the tubes are done and crumbling apart. Will I be OK with fuel-line from auto zone connecting these two vents?




(I did not write "can I plug this" I grabbed this from another thread for display purposes only)

[MCRider]

A 78 clears it up a little, as they are different than K2. The breather from the cam cover of the 78 engine goes to the airbox. I would not connect it to the tank. I'm not sure but I think the 3rd tube on the bottom of your tank still goes to the engine. As long as that can be confirmed I would do that rather than blocking off the engine tit.

Look in the tank or run a wire up that third nipple and see that it is a stand pipe going to near the top of the tank.

If the vent on the tank takes the same size hose as the engine case, that's definitely where I would put it. IF you've done away with your airbox, run that cam cover vent to the atmosphere the way the K2s and several Ks later did it.

The way god intended.   

[SKTP]

Found this...that is what I plan on doing also...seeing oil on my tire is sketchy



From:
http://forums.sohc4.net/index.php/topic,94278.msg1117090.html#msg1117090

[MCRider]

Found this...that is what I plan on doing also...seeing oil on my tire is sketchy



From:
http://forums.sohc4.net/index.php/topic,94278.msg1117090.html#msg1117090

That's the ticket!

Took some searching.

[SKTP]

Tube in place...long ride around town last night. No drips this morning. I am beginning to think I only have a tach-seal leak now?!!!! I hope that is the case...I have been wiping it and so far no drips under the atl-cover overnight at all....come on no head-gasket leak! Also now that I have a tach, the bike is way more fun. First oil change (or this rebuild) coming soon!

this is next

[SKTP]

Drove 83 miles yesterday. Long Beach to San Clemente and back along the PCH.

Top speed was 77mph...I need to really remember my rpms to speed ratios... How do you read this thing?

It would be 3rd gear 5100rpms = 50mph



The oil-vent/allover the swing arm leak is fixed...there is a small leak on my clutch cover (I think)....might be the oil-line connection? Need to investigate more.

The head seems to be not leaking/the rope is holding longer this time...will be changing out the tach seal soon...




Ripped all around on this one Saturday

[RandyBMC]

Beautiful pics - you've got some nice riding available close to you!  Envious.  I'm glad your tank vent fixed the issue.

[SKTP]

Thought I would color this one so it would be easier to read



this chart was found on page 10 (actually 12 in the PDF)

http://moto-odejda.ru/file/CB750SOHCShopManual.pdf

[SKTP]

Am I reading this right? 100mph in 5th at 4000rpms?

I am pretty sure in 5th at 70mph I am way higher than that....I better count my sprocket teeth

[RAFster122s]

I think that the blue lines would represent your speed to rpm reading... I am not sure how to read the % figures... the curves with the gear change speeds for the top end of that gear's usage...on the bleeding edge of something going pop!