Topic: 1978 CB750K — Post 836 OIL PRESSURE - Hopefully Good!?

[SKTP]

Ok...my main shaft seal is leaking too much...I will be pulling and replacing at the next oil change. Should I do the frame kit at this time...and if so, which one is best?

[SKTP]

Well I am going to think about it...might just pull the motor conventionally because I need to change out the main-shaft seal (didn't seat properly)

That's it right? #10 It is behind the points

[MCRider]

Well I am going to think about it...might just pull the motor conventionally because I need to change out the main-shaft seal (didn't seat properly)

That's it right? #10 It is behind the points

Yeah, the tube kit won't help much if you gotta split the cases anyway. But its nice to have for top end work.

Helps a little when the tubes are gone to get the whole engine back in.

[madmtnmotors]

I've read reports of that seal being replaced without splitting the cases. Yes, there is a lip on the inside of the seal, but the process involved grinding a bevel on the outer edge of the case opening to get the lip started into the case and using the advancer shaft with washers and a collar to press the seal into place. A little permatex anaerobic sealer around the opening would also help provide some lubrication. If it fails you're only out the cost of the seal. If it works you saved a lot of work. 

If you're concerned about damage or over stressing the advancer shaft (as well you should be) you could use a plate bolted to either the points cover bolt holes, or maybe the points plate bolt holes. An old points plate could even be "pressed" into service as a backing plate for pressing the seal into place. The search function for the site is now functional again so I would expect the relevant thread(s) could be found.

[SKTP]

I did ask this question before and did search and did find the member that replaced the seal without splitting the case.

http://forums.sohc4.net/index.php/topic,167112.msg1933186.html#msg1933186

I forget if it was in PMs or where it is. But I was told the seal eventually started leaking again and they split the cases and replaces the seal for the OEM one.

This will be my 4th case-split but my first Bottom-Only split so I think I feel pretty good about it.

I will need: the Oil-seal, Trans gasket, Clutch gasket, oil pan gasket, and I think that's it?

[madmtnmotors]

Ahhhh.... I was not aware of the follow up regarding the eventual failure. Yes, it does seem as though you have had plenty of practice now, you'll soon be able to split the cases in your sleep.

Or was that nightmares? 

Hang in there, you've come this far! 

[SKTP]

It is not even THAT bad of a leak...but...it leaks directly onto my exhaust pipe and at night, it looks like I am steaming like a hot tub on a cold night.

[SOHC4 Cafe Racer Fan]

I agree that you can probably flip it over and just disassemble the cases.

[01Thomas]

Don't forget the alternator gasket.

I did ask this question before and did search and did find the member that replaced the seal without splitting the case.

http://forums.sohc4.net/index.php/topic,167112.msg1933186.html#msg1933186

I forget if it was in PMs or where it is. But I was told the seal eventually started leaking again and they split the cases and replaces the seal for the OEM one.

This will be my 4th case-split but my first Bottom-Only split so I think I feel pretty good about it.

I will need: the Oil-seal, Trans gasket, Clutch gasket, oil pan gasket, and I think that's it?

[SKTP]

Drove 88 miles or so today. From Long Beach, up the 710 to the 405 to the 110 to all over LA...across Santa Monica BLVD to Pacific Palisades...down PCH...to El Segundo...over to the 405 and home...there's still leaks....the suspension leave a lot to be desired...but it was a fun day...oh yeah, top speed via GPS: 83.7mph

[andy750]

Great photo! Bikes not bad either

[SKTP]

Strange...seems like multiple recents post in this thread have been deleted?

[JoeCooley]

Site crashed. Last good backup was Dec10th.

[JoeCooley]

I will take a pic of my breater setup tmrw.

[Tintop]

Site crashed. Last good backup was Dec10th.

Ok, so it's not just me being off line for a couple of days.

[USMC5811]

Site crashed. Last good backup was Dec10th.

Good to know - I thought all the moderators were mad at me...again


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[JoeCooley]

Well I forgot to get the picture for you. Now it's back together. I had actually wrote out a long post about how mine is setup. I guess I'll do again. Haha.

Ok so 3 hoses. Top, middle, and bottom. Top goes from separator to the airbox, middle is from the valve cover to separator, bottom is a drain. The bottom may have a little peacock on it to drain the oil that collects. Mine just has a bolt in it. I had my air/oil separator apart recently and stuffed it full of steel wool to catch the vapors. I don't have the factory air box so I just vent the top hose by the carbs. There is also a hose from the oil tank to the transmission. I believe this a pcv vent also.

Hope this helps. I remember you asking about a diagram for the system earlier in the thread. Maybe it's gone now?

[SKTP]

Well, here's the new plan.

I was going to get an RC51 and give the CB a rest, but instead, I have decided to pay somebody to rebuild my motor. The last ride I went on the bike really started leaking and it is smoking out of the top breather way too much. So since I will have the motor out for the 4th time, why not throw this in there?

http://www.dynoman.net/bikepages/sohc/packages.html

Now I need to figure out pistons. Are 78K piston more like F bikes?

[JoeCooley]

Well, here's the new plan.

I was going to get an RC51 and give the CB a rest, but instead, I have decided to pay somebody to rebuild my motor. The last ride I went on the bike really started leaking and it is smoking out of the top breather way too much. So since I will have the motor out for the 4th time, why not throw this in there?

http://www.dynoman.net/bikepages/sohc/packages.html

Now I need to figure out pistons. Are 78K piston more like F bikes?

Here's a post from a while back to explain things. http://forums.sohc4.net/index.php?topic=6742.0

Essentially the 75-76F & 77-78k had the same pistons. A very slight dome. The main difference from these engines and the older engines is in the cylinder blocks. Honda added the big oil o-ring things to help with leaks. F2/3 pistons are a breed all their own. Those pistons with a K head will result in hi compression due to the smaller chambers of the K's.

[SKTP]

So thanks to Don, I have hired a mechanic to hopefully re-do my motor once and for all. He came and picked the bike up on Saturday and I am very excited to have a pro go over it.

From our conversation I now suspect that my engine-studs have been stretched out and I was unable to actually torque the head to spec. Also my oil-pump is allowing the side tank to drain all the way into the sump, so when I checked my oil and thought it was low, I most likely over-filled the bike thus causing the many new leaks that occurred on my final ride of my last attempt. I may have installed the rings incorrectly resulting in the blow-by...plus the shaft seal not sealing + possibly one of the cam-tower seals not sealing...anyways. I learned a lot, but apparently not enough yet...looking forward to updates as he goes through the bike. Thank you again Don

[SOHC4 Cafe Racer Fan]

So thanks to Don, I have hired a mechanic to hopefully re-do my motor once and for all. He came and picked the bike up on Saturday and I am very excited to have a pro go over it.

From our conversation I now suspect that my engine-studs have been stretched out and I was unable to actually torque the head to spec. Also my oil-pump is allowing the side tank to drain all the way into the sum, so when I checked my oil and thought it was low, I most likely over-filled the bike thus causing the many new leaks that occurred on my final ride of my last attempt. I may have installed the rings incorrectly resulting in the blow-by...plus the shaft seal not sealing + possibly one of the cam-tower seals not sealing...anyways. I learned a lot, but apparently not enough yet...looking forward to updates as he goes through the bike. Thank you again Don

The cool thing about Bill is hanging out and learning from him.

[SKTP]

UPDATE: So I have an experienced mechanic going through my bike to see why it is leaking. Turns out the cheap Harbor Freight torque wrench probably has a lot to do with it. He told me that my engine studs were at 16lbs and that some of the smaller hardware was just finger tight. Lesson learned.

Also, if you have been following my never ending build, the shaft seal leak wasn't a shaft seal leak...turns out there's an O-ring on the timing shaft that I never changed out...he put in a new one and that leak was gone!

[SOHC4 Cafe Racer Fan]

UPDATE: So I have an experienced mechanic going through my bike to see why it is leaking. Turns out the cheap Harbor Freight torque wrench probably has a lot to do with it. He told me that my engine studs were at 16lbs and that some of the smaller hardware was just finger tight. Lesson learned.

Also, if you have been following my never ending build, the shaft seal leak wasn't a shaft seal leak...turns out there's on O-ring on the timing shaft that I never changed out...he put in a new one and that leak was gone!

Something tells me that HF torque wrench is either going to be mangled, thrown away or both!

[SOHC4 Cafe Racer Fan]

 

I wish I had that kind of disposable income. 

[SKTP]

Obviously when I click the link it is down for a system update....<sad trombone sound>

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