Topic: CB750K4 what did I get myself into?

[newday777]

The second picture is the top of the air box mounting bolt.

[BrockCB750]

Great! Thanks newday777. Much appreciated!

[BrockCB750]

Before and after on the engine!

[Stev-o]

Wow...that engine looks great!

BTW - I'm a big supporter of powdercoat on frames, it is so much more durable. Have not had an issue of chipping it when installing a motor on a couple of my projects. Just need to protect the frame same as if it was painted.

[Floshenbarnical]

Before and after on the engine!

What a transformation! Doing god's work, resurrecting these tired old girls!

[BrockCB750]

Got a local-ish guy (MotoRelic) to help with frame hoop, battery, seat pan. electronics tray...





At this point I decided to go with powdercoating the frame and swingarm instead of paint.

[BrockCB750]

I didn't really consider that. Crap.

What are my options to mitigate that problem? The bike will be significantly lighter it will also never have a passenger. Can I just stiffen up the shocks a little above normal?

Thanks!

[Mark1976]

Wow...that engine looks great!

BTW - I'm a big supporter of powdercoat on frames, it is so much more durable. Have not had an issue of chipping it when installing a motor on a couple of my projects. Just need to protect the frame same as if it was painted.

   Without a doubt the best way to go, I refuse to paint frames these day, why do it when you can pay someone else to do it for ya, it's better looking and more durable and just easier.

[Floshenbarnical]

Wow...that engine looks great!

BTW - I'm a big supporter of powdercoat on frames, it is so much more durable. Have not had an issue of chipping it when installing a motor on a couple of my projects. Just need to protect the frame same as if it was painted.

   Without a doubt the best way to go, I refuse to paint frames these day, why do it when you can pay someone else to do it for ya, it's better looking and more durable and just easier.

But a can of Duplicolor cost $10 and it looks almost as good.

[BrockCB750]

Can someone confirm that my oil jets are installed correctly??

It feels weird that they sit in there loose like that:

[PeWe]

CB750?
NO, the oil orifice should sit flush with the head surface cam holders sit on, not raised.

O-ring look too thick.
Stock size needed, 5.8x,1.9mm
I have tested viton 6.0x2.0mm, too thick, o-ring cracked with risk of blocking the oil.
O-ring need space sideways when compressed.

[BrockCB750]

PeWe thank you! The jets needed a little nudge to seat correctly. Does this look better? Also swapped the oring.

[PeWe]

Much better!
The o-ring should raise a little over the surface so it will compress when tighten the cam holders.

Do not forget the other o-rings. There are 4. The other seal the end of oil feed to the cam and rockers.

[BrockCB750]

Are all 4 supposed to be the same size? Looks like they are 4x required in the parts diagram.

The two I put on the oil jets had to be stretched around the oil jet. As in the inner diameter was too small to just lay flat around it. They would look too small in the two other non-oil jet locations.

Sounds like I just need I order exactly the correct size. The parts blowout calls for 5.8x1.9 91305-323-000 like you said. I am going to break out my meter and measure all the rings in the kit and if none match order new ones from Honda.

[PeWe]

The earlier heads have different oil orifices and different o-rings.
Here a K2 head to zoom in with a bag of o-rings.

[BrockCB750]

Dropped the frame, swing arm, oil tank and engine mounts, etc off at powder coat. Powder coat won out.

I got the head on the other day, looked at my bag of gaskets/o-rings from the kit and realized I had 8 cylinder stud gaskets I never put in. I got to reading and watching a couple youtube videos and am I crazy or do people not put these gaskets in sometimes? These are called "GASKET, CYLINDER STUD BOLT" in the parts diagrams.

Here is what I am talking about (pictures after I put all 8 in):




Since I had the head off another questions that feels REALLY dumb. In the case of the head gasket I am using which end goes up? The writing side up, or non-writing side up? haha. I feel like a dumbass asking that.

Also, is this a decent quality gasket?

[PeWe]

Head gasket only fit one way.
Usually wrong first time independent of how you do!

[BrockCB750]

PeWe really appreciate you taking the time to reply.

Yeah woke up this morning and remembered its all offset a little bit so it can only fit one way. Probably why I didn't ask before, haha. I am getting REALLY paranoid now that I am probably three weeks away from starting everything up. Really don't want to find out I did something dumb like missing an o-ring or gasket and trash the engine.

I watched another video of someone reassembling the head and they didn't use the head bolt gaskets mentioned.

I also did some reading on CycleX and other places and this it what it sounds like to me:
1) There were head bolt gaskets pretty early on but not in the first couple engine interations.
2) There were oil leak issues.
3) Dowels and head bolt gaskets were added to help resolve that issue.
4) Later on larger sized head bolt gaskets were added to further resolve that issue.
5) They are not totally necessary today because head gaskets are better? Not just the MLS ones like what CycleX sells.
6) The larger head bolt gaskets that come in kits are fine to use and cause no issues but may not be necessary anymore.

Does that all line up with reality?

If so I am just going to use them since I have the head off the engine again.

I don't know what the hell I would do without this forum!

[newday777]

"Also, is this a decent quality gasket?"
Who is the gasket from?
Hondaman says he uses the Veserah gaskets on his engine builds.

"2) There were oil leak issues."

I stopped by a friend's shop yesterday that is a longtime race engine builder. Kurt Jordan. He worked for Action Fours back in the 70s and would occasionally get to take some of the customer bikes to the dragstrip(per the request of the customer) to get the ET times of the build to see if they would produce the claimed increase the Action Fours said would happen in their ads. He also track raced his own bikes. And he has engineering degrees. He also at 70 yrs still remembers most details of his engine builds and the associated customer.(he still has all his notebooks on each build to refer back to when needed too)
In our conversation he mentioned that the leaks (and iterations of the 750 motors) were from the lack of heat cycling of the motors to retorque the head bolts because of the lack of room in the frame to pull the head cover off to retorque the following day after cooldown.(at the factory and when dealers warranty replacement of head gaskets because of the leaking head gaskets)
So what he does is to do a heat cycle with a propane torch to mimic a run engine for heat cycling. Then retorque it the following morning after it cools down. He also says he likes using the MLS head gaskets as the take less amount to retorque after cool down. The important thing is to heat Cycle it to retorque before putting the motor back in the bike.

(Hondaman or maybe Mike Rieke use a salamander construction heater to get the motors up to temp for heat cycling, CycleX has a mule test stand to run the motors on to heat cycle.)

[BrockCB750]

Getting very close to buttoning the engine up.

Also, probably a risk putting all this effort into the bike and not having it tagged and titled in my name first but took care of that this morning. Got through the abandoned vehicle process. Also, have my motorcycle endorcement finally. Definitely two things that could have been done before but thankfully went well. haha

[HondaMan]

I'm a little late to ask this, but...did you have the top of the cylinders milled down 0.010" when they were bored?
If not, and if you didn't get some thicker O-rings for the 2 oil ports thru the head gasket, it will leak oil. I can send a pair for free: I try to 'catch' builders here first so they don't go thru all the work, only to get leaking between the head and cylinders.
I used both" mill the cylinder deck 0.010" to match up to the modern head gaskets that are all thicker than Honda's OEM versions, by 0.2mm. Some of the MLS gaskets are thicker than that, even. Then, the O-ring (1.9x5. isn't thick enough to seal those oil ports.

[BrockCB750]

I didn't have the cylinders bored and no milling.

Very much appreciate you trying to catch a mistake!

I do have the engine all back together. Frame gets back from powder coat Friday.

Is there anything I can do now to make 100% certain I won't do anything to trash the engine? I triple checked the gaskets as I put it together.

I am getting a little nervous after all this work.

[BenelliSEI]

Did you manually prime the oil pump?

[BrockCB750]

Frame, swingarm, other stuff back from powder coat!

With a little help from the wife engine is in the frame

This is really going to pick up steam it feels like.

[BenelliSEI]

Looks very good!