Topic: CB750K4 what did I get myself into?

[MRieck]

The small rubber looking spacers are not needed, they are said to reduce vibration noises, or some such issue as that.  I left mine out and I haven't heard any noises.

The parts may depend on what you find when you tear it down further and perform measurements.

You may need to go to an oversize piston/rings.

I have a lot of those fin buttons....if somebody needs them please let me know.
Mike

[HondaMan]

The small rubber looking spacers are not needed, they are said to reduce vibration noises, or some such issue as that.  I left mine out and I haven't heard any noises.

The parts may depend on what you find when you tear it down further and perform measurements.

You may need to go to an oversize piston/rings.

I have a lot of those fin buttons....if somebody needs them please let me know.
Mike

Mike: where did you find them? I sometimes need them for the cylinders I get for rebuilds.

[CycleRanger]

The small rubber looking spacers are not needed, they are said to reduce vibration noises, or some such issue as that.  I left mine out and I haven't heard any noises.

The parts may depend on what you find when you tear it down further and perform measurements.

You may need to go to an oversize piston/rings.

I have a lot of those fin buttons....if somebody needs them please let me know.
Mike

Mike: where did you find them? I sometimes need them for the cylinders I get for rebuilds.

You can still get those from Honda but they're pricey. ~$5.00 each!
12620-286-000

(Working on my '71 CL350 now and I was amazed to see that it still all the buttons except one.)

[BrockCB750]

After three days of soaking a stuck spark plug and testing each day if it would break free it did today... breaking off. UGHGHUGHUGHHHHH

Oh well, I already decided I was going to take it to the machine shop to get the points screw out. Just add it to the list I guess.

[denward17]

The small rubber looking spacers are not needed, they are said to reduce vibration noises, or some such issue as that.  I left mine out and I haven't heard any noises.

The parts may depend on what you find when you tear it down further and perform measurements.

You may need to go to an oversize piston/rings.

I have a lot of those fin buttons....if somebody needs them please let me know.
Mike

Mike: where did you find them? I sometimes need them for the cylinders I get for rebuilds.

You can still get those from Honda but they're pricey. ~$5.00 each!
12620-286-000

(Working on my '71 CL350 now and I was amazed to see that it still all the buttons except one.)

Are you guys indicating that they are needed?

[CycleRanger]

The small rubber looking spacers are not needed, they are said to reduce vibration noises, or some such issue as that.  I left mine out and I haven't heard any noises.

The parts may depend on what you find when you tear it down further and perform measurements.

You may need to go to an oversize piston/rings.

I have a lot of those fin buttons....if somebody needs them please let me know.
Mike

Mike: where did you find them? I sometimes need them for the cylinders I get for rebuilds.

You can still get those from Honda but they're pricey. ~$5.00 each!
12620-286-000

(Working on my '71 CL350 now and I was amazed to see that it still all the buttons except one.)

Are you guys indicating that they are needed?

Not unless you are going for a concours restoration.

[newday777]

The small rubber looking spacers are not needed, they are said to reduce vibration noises, or some such issue as that.  I left mine out and I haven't heard any noises.

The parts may depend on what you find when you tear it down further and perform measurements.

You may need to go to an oversize piston/rings.

I have a lot of those fin buttons....if somebody needs them please let me know.
Mike

Mike: where did you find them? I sometimes need them for the cylinders I get for rebuilds.

You can still get those from Honda but they're pricey. ~$5.00 each!
12620-286-000

(Working on my '71 CL350 now and I was amazed to see that it still all the buttons except one.)

Are you guys indicating that they are needed?

You know that there aren't buttons in between all the fins?

[BrockCB750]

After breaking off the spark plug in the head I decided to take a pause and read ahead a bit in the CB750 book to see what I had ahead of me.

Not thrilled at all about "the hardest part of this disassembly may be now facing you". I am patient and don't mind going slow so maybe removing the head won't be that bad...

Also, scared about what I am going to find as far as corrosion and rust once the head is removed. I am optomistic because all 4 spark plugs were in the head and all the very dark black oil that came out when I drained it while dirty didn't seem to have any water or sparkley bits in it. So far everything that has been exposed to the elements (breather cover fasteners, valve cover fasteners, spark plugs, points cover fasteners) have been a huge PIA. Everything inside the engine has gone pretty well. I am Hopeful.

Wish me luck!

[BrockCB750]

Pulled the cam towers off and found an unpleasent surprise...

Looks like a whole spider community lived in here.. one of the former residents was found preserved in the oil.







I am guessing the spiders lived in harmony with the wasp colony that took up residence in the engine fins:



Everything is two steps forward one step back lately! haha

[newday777]

Vapor blast them suckers out a theyah.

[HondaMan]

I take them to my machine shop when they look like yours. They love to put them thru their parts washer machine. They said the inside of it looks like 3 cyclones battling with each other, throwing solvents. When I get them back they look new! 

I see heads and cylinders like that a LOT. Mud dauber wasps and several types of spiders. When I took mine apart in 2013, though garage-kept, there were 2 well-cooked black widow spiders in the head, one on each side. One was BIG.

[PeWe]

BrockCB750,
watch out when you remove the 4 small M6 bolts in the cavities the rubber coins covered.
Dangerous spiders!

We do not have anything here that can bite worse than a wasp sting. Except for a mild viper snake.

I have wondered if parts ordered from USA or Venezuela once should contain any extra passengers.

Good luck finding all bolts that keep the cases together.
Very easy to miss one or 2 so do not use excessive force to open the cases.
Count them. CMSNL part chart show them all.

[BrockCB750]

Went to remove the 4 small bolts in the cavities... realized I likely need a long impact driver bit? Tried a regular JIS 3 screwdriver and its not going to break free  with that. Tried the thinnest walled 10mm socket I had and it was slipping off just spinning it with an extension by hand without a wrench.

In the book it says to use a flat wrench. That does not seem to be the case with my head? Am I correct in that I need to go get a long JIS 3 impact driver bit?

I misread, says the outside ones can be reached with a wrench but "A thinwall 10mm socket, or Showa T-handle 10mm, may be required as the crosspoint heads will usually strip in the attempt, if corroded." for the inboard ones. The picture shows a wrench so my brain got confused. haha

I am not even going to attempt to use a JIS3 cross point given how everything else has gone. I guess my new questions are:

1) Since none of my 10mm sockets are thin walled enough does someone have an amazon or other link to one that would work?
2) Lacking a socket suggestion, does someone have a 10mm T-handle that will be thin walled enough?

Thanks everyone!

[seanbarney41]

sometimes you can put the driver bit in a socket, put the socket on an extension, extension on the driver and do it that way.  Never had any trouble using 1/4" drive regular socket on those.  The torque spec for them is low but they are probably at least somewhat stuck

[BrockCB750]

sometimes you can put the driver bit in a socket, put the socket on an extension, extension on the driver and do it that way.  Never had any trouble using 1/4" drive regular socket on those.  The torque spec for them is low but they are probably at least somewhat stuck

I tried the bit in the extension, immediately started to strip the cross-point head out. Its weird I have about 5 or 6 different 10mm sockets and none of them seat nicely at all. I guess I could try to hammer them on but that seems like a really bad idea.

Let me dig around more and see if I can find something with an even thinner wall. Running out of places to look though. haha

[denward17]

Use a pick or something to dig out all the dirt particles from around the bolt.

[HondaMan]

I can offer this, having stumbled into it recently: at Harbor Freight they have a 1/4" drive socket set with a 10mm socket that fits. You'll have to also (probably) get their 3/8"-to1/4" adapter, but it works, and is cheap!

[BrockCB750]

Thank you everyone! I found a 1/4inch Craftsman 5 point long socket that finally worked. They came off without too much of a fight.

So embarrassing but I bought these harbor freight magnetic socket organizers and the first ones I attempted to organize was the long 1/4". I didn't finish and left the organizer in the top of the tool box covered with a bunch of crap. Figures it was that ONE out of a dozen (admittedly only one other 1/4") that worked.

I felt like I had taken crazy pills.

[BrockCB750]

Got the rest of the bolts loosened. Following the correct order.

I am asking lots of questions as I go just because I really hate forcing things and when I hit that wall I feel like I need to stop and ask people here who have a lot more experience so I don't make a catastrophic mistake. I appreciate everyone talking me through that.

[RAFster122s]

Did you take a hammer and give the screw a good hard smack or two? It can sometimes make the difference to break them free without stripping out the head. Impact driver is sometimes a good tool for removing case screws because of the galvanic corrosion that sets up sometimes.

[seanbarney41]

No worries...your questions are good.  It's fun for us to help you successfully

[PeWe]

If your questions cover everything plus all mistakes that is likely to make, this thread will help others doing this for the first time or too long time ago

[BrockCB750]

Some good news got the head off without too much trouble which really surprises me but I am just going to take this as a win and not think too much about it. Hoping it doesn't mean there was a severe overheat situation or warpage that allowed it to come apart much easier than expected. Didn't spend a ton of time inspecting the gasket but it looks fine?

Not sure what comes next because I thought this part would take me a lot longer...

[denward17]

Not sure what your overall goal is, but I would check for valve seat leakage with some type of fluid in the ports.

If leaking take valves out and repair, check valve guides and seals.

Take cylinder off and inspect pistons/rings/cylinder walls, clearances and such.

[calj737]

Not sure what your overall goal is, but I would check for valve seat leakage with some type of fluid in the ports.

If leaking take valves out and repair, check valve guides and seals.

Take cylinder off and inspect pistons/rings/cylinder walls, clearances and such.

Before you start tearing the motor down further, what is the original mileage? Often, you create issues when none exist in an attempt to verify conditions that would otherwise not be an issue on a low mileage motor.

For instance, you can rotate the crank and do a visual inspection on the cylinders without disrupting the seating. Drizzle a bit of oil in them and see if the rings wipe the oil. It's not as exact as a bore mic, but it is pretty reliable.