Topic: Cylinder stud gaskets?

[JerrodR]

What's up guys, head gasket on my 74 750 Four let go last week, And I just got the head off today. The issue I'm having is when I pulled the head off, I was missing 2 or the cylinder stud gaskets. I'm sure they didn't fall off and roll somewhere, I had my eye on the entire separation. Rode the bike for 2 weeks and it didn't leak a drop of oil until the head gasket went. I would think that these cylinder gaskets serve a purpose, how is this possible? Only thing I can come up with is the previous dude inside this engine, substituted the gasket's with form a gasket or something. Any ideas on what going on here?

[Alan F.]

Pictures please, too abstract without them.

[bryanj]

What do you mean by cylinder stud gasket?

[PeWe]

O-rings for oil transport to head?
Low/no pressure due to leak, goodbye cam , holders and rockers.

[Alan F.]

These go on the rear 8 studs between cylinder and head.

There is a note in the parts listing on Partzilla, "Use from engine SN 2352923"

https://www.partzilla.com/catalog/honda/motorcycle/models-with-no-year/cb750k4-a/cylinder-piston



https://www.partzilla.com/product/honda/12115-300-000?ref=74a5dc2be4753575a295da61b9c8b32b93313152

#2 in this diagram:

[JerrodR]

Yep, that's them, and one of my Rocker holders did get hurt, I thought it was because I had to ride it home after the head gasket went..

[JerrodR]

Either way, I ordered a new Rocker Box, and the missing Cylinder stud gaskets.

[JerrodR]

The Cam was slightly discolored from excess heat where it was seated in that Rocker Box, but it seems the only thing that was actually damage was the Rocker Box, it spins fine. I didn't even know there was anything wrong until I noticed the little oil feeder hole wasent on both sides in the Rocker Box.

[Alan F.]

I'm a little confused, the two center rear studs are the oil feed to the head, that's why they have o-rings. Why would these seals be used on those studs? I think this may be what your PO was thinking.

[bryanj]

Please look in the manual and use the correct terms, you are confusing my aged adled brain
Cam Tower not rocker box
Seal not gasket

And looking at the discolouration on the bearings your cam is now junk as are the rockers, you need to find out why oil wasnt getting there as gasket had nothing to do with it and those tubular seal wouldnt either

[PeWe]

Those are for oil return, no harm to top end if leaking.

[Alan F.]

I thought oil return was at the front of the engine?

[JerrodR]

Blown head gasket, had to ride it home from about 15 miles out, the new (Tower) I ordered comes with rockers.

[JerrodR]

And that's what the parts were labeled as in eBay when I ordered them, I'm not a machanic,  just a dude who doesn't have the money to hire someone, and I want my bike back..

[Alan F.]

No point to hiring someone who is less familiar with your bike than you are. You're in the right place to get the best help and guidance there is for your bike.

[JerrodR]

Couldn't agree more, I found a complete head assembly on eBay, has everything but the head itself, for $160.00. went ahead and pulled the trigger, cause yeah on second look that cam bearing looks pretty rough.

[JerrodR]

Says it will be here on Friday at the latest, Guess I'll take this time to give me mateing surfaces a solid cleaning. I already stripped and painted the frame, and power washed the old paint of the Lester's. They didn't look so hot. Pretty decent now though.

[JerrodR]

Ok, this concerns a bit. Apparently the head assembly that I have coming is out of a Hondamatic, the guy says it will work fine, and I can't see a reason why it wouldn't. But the Hondamatic claims half the HP of the standard 750, is this lost in the transmission? Or is putting this cam iny bike gonna result in a significant loss of power?

[PeWe]

There are manuals to read showing details how to do with all parts.
This is a must. Wrenching without reading will not work.

CMSNL.com has all charts of each model/year where parts are shown. There are small important stuff not to be forgotten and must be oriented or flipped correctly.

I used the crappy Haynes Owners Workshop Manual back in the 80's long time before Internet when there are tons of information, videos included.
Read 3 times wrench 1.

It cost a lot in gaskets only to redo things. If the engine must be pulled, oil too.

CB750 shop manual based on K0 with K1-K7 as additional chapters. Download pdf free copy
CB750
http://manuals.sohc4.net/cb750k/

This is also available as paper print.
My printed version together with Hondaman's book will never see the garage nor dirty hands.

https://www.ebay.com/itm/253176098304

Same seller has important tools for clutch nut and wheel bearing  retainers.

Mark Paris aka (Hondaman) Book. It has information not found elsewhere, except his posts on this forum as 'Thoughts of Hondaman'

Here good info too
http://www.hondachopper.com/garage/garage.html

More manuals
http://manuals.sohc4.net/#

It is more demanding to build a bike from parts than repair a complete stock bike. Or repair a bike where PO has done wrong or skipped parts.

Before a job it is very relaxing to prepare by reading.
I like the Youtube video that show how to assemble the shifting mechanism with springs and stuff to get it in right order at first attempt.

I did this several times in the 80's and had to get it right by testing.
No digital camera then to take photos how things sat before removal.

I usually take photos of each step of assembly. I hate to wonder if I forgot an o-ring or flipped a washer wrong.

My phone has a good camera as most phones have today with wide angle lens and night photo function. I seldom use my real camera. Last vacation phone only.

[754]

The A cam probably has less lift.
 For that $  you can always get a cam and rockers and cradles, but often not all rockers are good.or a whole engine, easy to pull rocker cover to inspect them.
 You could have asked on here, could learned  on here.
 Btw , and I am not reading back, did you say the motor was pretty fresh ? Because that is not a clean rocker cradle, and the second bearing is pooched on First glance, and it looks like flakes of rocker surface up top above the rocker oil hole.
 Why did you not post a pic as soon as you pulled it of the motor ?

[bryanj]

Cam tower and rockers from hondamatic will be fine. You should get all the seals needed in a top end gasket set BUT you need to make sure that all the oil passages and oil restrictor jets are super clean, i am talking auto box clean not car engine clean.
You need to replace the pucks under the towers and O rings at both ends of each tower, you also need a decent torque wrench and the downloaded Honda manual.
I have seen far too many 750 engines requiring majour work within a month of being assembled incorrectly and not clean enough

[JerrodR]

I have a Clymer's book if that will do instead of downloading manual?

[JerrodR]

And are the pucks you speak of the little rubber things I had to remove to get to the center head bolts?

[754]

Comer manual should work, it sure did for me..

[bryanj]

Yup

[PeWe]

About cams. I have found K7/K8 1977-78 cam for good price when K0-K6 cost much more.

The K7 cam has a molded ring  beside tacho gear.
Last one with sprocket and end washer on from a low miler, $50US.

The first cam complete with sprocket, cam holders, rocker arms and shafts with most screws. Not much over $100US.
Also a low miler and not much wear.
But this was a few years ago.

Is this a later F cam?
The squares beside tacho gear look familiar.
https://www.ebay.com/itm/401926328658

[ekpent]

And are the pucks you speak of the little rubber things I had to remove to get to the center head bolts?

The pucks are about the size of a nickel but you have identified those. The 4 little orings go under the cam tower two at each end and are very important. Were they there when you tore it down ?