Author Topic: 1978 CB750K — Post 836 OIL PRESSURE - not good (Read 248204 times)

madmtnmotors · « **Reply #875 on:** December 29, 2015, 04:44:09 AM »

Quote from: SKTP on December 28, 2015, 08:53:15 PM

those holes for the pins are very deep...can't be from the resurfacing...

That may be true, but the pins can stick out quite far as well. It's easier to measure these things while it's apart.

It does look like the rivets were an issue, but there could always be more than one problem...

You could mill, drill or grind small reliefs for the rivets in the mating surfaces too, so if the next guy uses the same gasket there would not be any issue.

SKTP · « **Reply #876 on:** December 29, 2015, 10:22:16 AM »

I have it apart. It is easy to see that the pins are not the issue. Plus I've had this engine together before with a thinner "normal gasket". And again, you can easily see the pins are not too long for the the holes they go in...

I am thinking I am just going to snip off the 2 rivets under the the "half circles"...then the concern is; will the MLS gasket stay lined up? (with an extrat set of hands, I think it would) Maybe I should just get a regular gasket and consider the MLS as a loss...

I'm going to call Ken now and see what he thinks

LINK to Torque Tables http://www.salocal.com/sohc/tech/torquetable.htm

SKTP · « **Reply #877 on:** December 30, 2015, 02:09:46 PM »

Just got a call from Ken. He seems like a really cool guy. I sent him photos. From our conversation (and that I measured the pins and holes) it must be the rivets (especially due to the marks it left). My main question was should I cut the 2 interfering rivets off? Ken told me to smash them flat...finger's crossed.

SKTP · « **Reply #878 on:** December 31, 2015, 11:35:58 AM »

Talked to Ken. Crushed the rivets flat in a vice. They now easily clear. Measured the locator pins and the hole depth. That all checks outs.

I can still see a little light at the edged after the initial torque down (following the sequence and done on 4 steps very gradually) with a torque wrench

I can fit the two very smallest feeler gauges I have into the sides of the gasket (but not up near the locator pin) I am now thinking the cylinder need resurfacing...can't hurt

Question: What is the proper re-torquing procedure? Do you just check that it's still at 15 or do you back it off in sequence and re-tigten?

This engine is fighting me every step of the way

I think if I had not had the inital rivet issue...I would never have noticed the very very small gaps or even have thought to check with a light

I found this thread http://forums.sohc4.net/index.php?topic=136281.0 that seems to be expressing the same issue...could I just be being paranoid?

SOHC4 Cafe Racer Fan · « **Reply #879 on:** December 31, 2015, 01:48:34 PM »

Those rivets just needed to go on a diet! Great that Ken helped out.

Typically, re-torqueing the head involves loosening and retightening. Are you using HD studs? If so, you can torque to much higher values.

madmtnmotors · « **Reply #880 on:** December 31, 2015, 03:15:28 PM »

Quote from: SKTP on December 31, 2015, 11:35:58 AM

I can still see a little light at the edged after the initial torque down (following the sequence and done on 4 steps very gradually) with a torque wrench

Did you check the head and cylinders for flatness with a straightedge while it was apart?

SKTP · « **Reply #881 on:** December 31, 2015, 03:41:50 PM »

I sort or tired...that seems like a most difficult thing to do than say...I have a metal ruler...I put it on its side across the surfaces...hard to say if the ruler is flat let alone the surfaces

For People with MLS head gaskets: Is yours 100% squished solid everywhere? Have you tried to stick a feeler gauge in between? or a light on the edges? (I don't think I would have even noticed the tiny tiny gap at all had I not had the rivet issue)

I'm not at the bike right now so I can't check what feeler gauges fit...it was the smallest and the second smallest of the Craftsman set that I have...It must be the surface flatness...what else is there? Unless the gasket doesn't get 100% squished everywhere (and that makes little sense)

APE's website says $30: LC350 Surface block or cylinder head 30.00

http://www.aperaceparts.com/machining.html

Since they already did the head surface...can't see how this could hurt (other than time)

I will get this bike together!!!!!! Happy New year and thank you for all of your help

754 · « **Reply #882 on:** December 31, 2015, 07:33:50 PM »

The only relative flat surface most folks have access to is window glass....
Check your ruler against that.. Hope its not a flexible rule..

SKTP · « **Reply #883 on:** January 11, 2016, 11:08:40 AM »

Progress

I have torqued and re-torqued with 2 different wrenches. I am going to try my luck with the MLS

More progress made this weekend...

I used this stuff, this is the photo from Hondaman's book, the stuff now looks liek this http://www.tacomascrew.com/Products/Adhesives/Permatex-80016-2BR-Form-A-Gasket-No-2-Sealant?gclid=CP75vtK5osoCFZKCfgodhOMDqQ or I hope it does...

O-rings are in there and the jets are cleaned

Sealing those pucks and I used thread sealer on the cam-tower-studs

TDC

my case has a tiny chip out of it right at the TDC mark...

forgot these broke off in the alternator wires...took forever to get then out. But I have a new harness for the male side

getting closer

SKTP · « **Reply #884 on:** January 17, 2016, 11:19:56 PM »

Engine in the frame!

These wires are so oil stained it difficult to know which one is green and which is the Blue-red. I picked the green to greenish one

The sprocket's raised side faces out like this right? (Couldn't find any good photos in books)

SKTP · « **Reply #885 on:** January 20, 2016, 10:21:46 AM »

Bumping for the above sprocket and wires questions...can't wait for the weekend!

RandyBMC · « **Reply #886 on:** January 20, 2016, 10:46:32 AM »

Mine has a big washer on the outside face with the raised part of the sprocket inward. I didn't touch it, so it may be right or wrong, but that's how it was.

SKTP · « **Reply #887 on:** January 20, 2016, 11:09:18 AM »

The older style appear to have the raised part facing out

and here's a 77 I just found

One more...I guess they would have drawn the raised surface if it faced out? Raised bit in it is!

seanbarney41 · « **Reply #888 on:** January 20, 2016, 04:22:58 PM »

The older bikes have raised portion on both sides and are actually overall thicker. It is hard to get correct thickness sprockets for the 77/78's. Most sprocket companies don't even realize that there is two different sprockets. I have resorted to just buying whatever cb750 sprocket and having the raised portion machined off on one side. Plus, then if your machinist is super pissed at you for grinding away at the bastard for an hour or so, you know you got a good, hardened steel sprocket.

That last picture is obviously wrong, as that set up won't allow the sprocket the necessary slight wobble once the bolt and washer are tightened. Every 77/78 I have seen has the flat side out.

Restoration Fan · « **Reply #889 on:** January 20, 2016, 05:30:29 PM »

Correct. The flat side goes outward. Putting the raised side towards the engine makes for that 10mm offset that you need on the 77/78's.

SKTP · « **Reply #890 on:** January 20, 2016, 05:33:46 PM »

Thanks guys...now the next question...what happens if I have the wires reversed due to oil staining?

seanbarney41 · « **Reply #891 on:** January 20, 2016, 05:45:25 PM »

your neutral light won't work unless you have low oil pressure

01Thomas · « **Reply #892 on:** January 21, 2016, 01:38:11 PM »

:-)

Quote from: seanbarney41 on January 20, 2016, 05:45:25 PM

your neutral light won't work unless you have low oil pressure

SKTP · « **Reply #893 on:** January 21, 2016, 01:59:56 PM »

I guess worst case it blows a fuse...It does appear to be the oil pressure indicator if I am reading this right

Restoration Fan · « **Reply #894 on:** January 21, 2016, 02:08:57 PM »

Quote from: SKTP on January 20, 2016, 05:33:46 PM

Thanks guys...now the next question...what happens if I have the wires reversed due to oil staining?

Which wires are you talking about potentially being reversed?

754 · « **Reply #895 on:** January 21, 2016, 02:15:58 PM »

You can check continuity to find that wire.

SKTP · « **Reply #896 on:** January 21, 2016, 02:49:54 PM »

Oh yeah...you guys are smart.

I'm talking about these 2...the wiring harness has nee out of the bike for almost a year..my head is just starting to wrap itself around wiring again

thanks

madmtnmotors · « **Reply #897 on:** January 21, 2016, 02:59:55 PM »

Quote from: SKTP on January 21, 2016, 02:49:54 PM

Oh yeah...you guys are smart.

I'm talking about these 2...the wiring harness has nee out of the bike for almost a year..my head is just starting to wrap itself around wiring again

thanks

Those look like the green and white from the field coil.

Also, regarding the three yellow wires, I usually replace the female bullet connectors coming from the stator on every bike I service. You see how nasty the male connectors were when you finally got them out? Well, the inside of the female bullet connectors will be in the same condition and these carry some of the highest current loads in the entire wiring harness. These can be replaced on the bike, it's tight but can be done. I start by cutting away the insulator from around the connector, then the wire can be cut right at the connector. This only sacrifices no more than 1/4" of wire. The connectors from Vintage Connections are awesome as long as the proper tool is used, as documented here:

http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494

madmtnmotors · « **Reply #898 on:** January 21, 2016, 03:06:35 PM »

Hit the insulation with a little shot of brakekleen. Also, slide the outer black plastic sheath back a little bit and you can usually see a cleaner section of the wire insulator to better able determine it's color.

timbo750 · « **Reply #899 on:** January 21, 2016, 03:43:15 PM »

Sometimes also you can scratch the dirty color back a little. If you have a steady hand you can shave off a poofteenth with a razor blade to find the color

Sent from my SM-G920I using Tapatalk

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Author Topic: 1978 CB750K — Post 836 OIL PRESSURE - not good (Read 248204 times)