Topic: My First Motorcycle: 1976 CB750F

[ZingZing]

Lots of CB750 engine parts on ebay.

If I get a good condition used camshaft I believe that I would need new rocker towers as well with at least similar wear. Is that true? I’ll post pictures of the bearings when I get home, but there was pretty good amount of wear on the bottom bearing.

[Jerry Rxman Griffin aka MuthaF'er]

Spare stock cams under my bed but can not guarantee what they came from. The F0/F1 cam was hotter than the previous midyear K's. Just not cutting loose with my hot ones. A hot cam would be a good investment considering a replacement may be necessary. After-market new replacement cam towers are available somewhere also. Maybe YaMiYa.com? 

[ZingZing]

There are some oil jets in the head with very small holes that can be blocked by silicone and dirty oil then this happens.

Yeah they were dirty but well everything’s dirty .

[ZingZing]

Does anybody know if any other bike’s rear calipers drop in to a ‘76 750F.

Nothing wrong with my brakes just can’t get them open. Tried heat, penetrating oil, and a whole lotta torque and I’d rather slowly take my time than ruin a caliper that’s listed for $200+ on eBay : .

Just wanted options if that caliper ends up being the last piece to the puzzle. Some of the DOHC Hondas that followed had similar looking rear calipers and the brackets separated from the caliper which would be convenient (for something). Most importantly it won’t be hard to pick one up for cheap.

https://imgur.com/a/KcFe7ui Something like this. It would also be convenient if I could reuse my old rotors as they’ve still got room to get resurfaced.

[Honda Hansel]

Hi
Looking for parts that inter changes with other models
Go to CMSNL.com
That where i go to look up part's that fits multi models
Look up @ Honda Cb750F1 1975/1976 model and locate the part and go to the button that says ...also fits other models .... a long list will come up and tell you what other models use this same caliper and bracket 

For the camshaft
You need a new one and new rocker arms and set screws (CMSNL has reproduction rocker arms that looks good I just bought a set made in Japan )
and you want to have the valves done as well
look at the valve stem on top and check the guides $$$$$$$$$$$$$$$
valves and guides can be found cheap and easy
The valve job will cost you a bit of cash $$$$

I just did my head for the CB750F2 1978 and the valves are expensive and the guides not cheap .Cost me $$890.00 Can dollar to do it 

Honda Hansel

[willbird]

You might be OK on valve guides and valve and seat condition. Worth cleaning it up and buying some valve lapping compound and see how they look. The "old school" valve lapping compound came in a double sided can, one side course and the other fine, I'd use the fine stuff.I agree there must have been some kind of oil problem to wipe cam lobes like that.  I see a 77F cam on Ebay for about 50 shipped. There is actually a complete head with cam, holders, rockers...the works for 230 shipped. I have seen people call stuff F that was not though, the later F heads are quite distinctive and I have seen some K heads being billed as later F's.

Bill

[Jerry Rxman Griffin aka MuthaF'er]

No other "direct" interchangeable replacement bike with the same part number for the 75/76F. Perhaps you can find a swap? If the 77/78 etc will FIT you might find the single piston is a better option. The 75/76 double piston is way overkill and can lock up the real wheel in a heartbeat. Too bad Honda didn't double the front instead.

"Can't get them open". Please explain. The overhaul kits have been available for a little while. I got mine from SiriusConInc.com   

A 77/78 F cam would go right in, no problems and be an improvement in performance. A 75/76 F cam would be an improvement as opposed to a 72 - 76 K cam.

Should you decide to do a head get a head marked 392 intake side top fin between 2 and 3. Do NOT get a black head with somewhat oval shaped chambers.

[Jerry Rxman Griffin aka MuthaF'er]

Push the pistons out with a grease gun on the bleeder valve before you take them apart

[ZingZing]

"Can't get them open". Please explain. The overhaul kits have been available for a little while. I got mine from SiriusConInc.com   

"Can't get them open" is #$%* talk by me complaining about not having a vise or clamps to hold the caliper while I wrench on it.

I just stuck two punches through the caliper into the gap between my driveway and garage which holds the caliper in place which is easy but really I just want to buy a bench vise but they're kinda expensive. And I gotta slav squat while doing this method which makes me look like a dumbass.

Push the pistons out with a grease gun on the bleeder valve before you take them apart

Godammit Jerry.

Both pistons and the front caliper piston are seized (clearly). If I put the caliper back together the grease gun method should still work right, making sure that o-ring that seals the brake fluid passage between both pistons is placed back. I also took the bleeder valve out from the front caliper but if I put that back I should also be able to grease gun that, correct?

[Jerry Rxman Griffin aka MuthaF'er]

LMAO but it's not funny. MANY frustrations doing what you/we have all done. We have to be very innovative. You do seem to qualify for that 

The grease gun is probably the best way to get the pistons out. If they are really bad the air gun method won't work and can be very dangerous if the piston decides to come out. It then becomes a VERY LARGE projectile under 120lb pressure or more.

[ZingZing]

Go to CMSNL.com

I love CMSNL. If I had the money, every single piece that's in stock would be replaced on my bike. Seeing all the parts with numbers, updated versions, non oe alternatives makes tackling a 50 year old back much less of a PITA. What a fantastic resource.

I have seen people call stuff F that was not though, the later F heads are quite distinctive and I have seen some K heads being billed as later F's.

Ebay is my last resort for used parts right now. Would much rather be able to see the parts in person, and I've been pretty lucky finding parts near me. Gonna have to do some research on how to properly lap valves at home.

It then becomes a VERY LARGE projectile under 120lb pressure or more.

Can't really improvise an air compressor so hopefully the grease gun does the trick. Turning a caliper piston into a Honda warhead does sound interesting though.

[willbird]

Go to CMSNL.com

I love CMSNL. If I had the money, every single piece that's in stock would be replaced on my bike. Seeing all the parts with numbers, updated versions, non oe alternatives makes tackling a 50 year old back much less of a PITA. What a fantastic resource.

I have seen people call stuff F that was not though, the later F heads are quite distinctive and I have seen some K heads being billed as later F's.

Ebay is my last resort for used parts right now. Would much rather be able to see the parts in person, and I've been pretty lucky finding parts near me. Gonna have to do some research on how to properly lap valves at home.

It then becomes a VERY LARGE projectile under 120lb pressure or more.

Can't really improvise an air compressor so hopefully the grease gun does the trick. Turning a caliper piston into a Honda warhead does sound interesting though.

The grease gun provides an easy 6k to 10k psi of hydraulic force, when you do the math on the piston diameter that is for sure an irresistible force :-). If one did a fair number of them one can convert a grease gun to use oil rather than grease for an easier clean up. I converted a cheap one to test each lubricating oil line on my Bridgeport mill when I replaced some of the lube system parts. Easy conversion really but it ruins the grease gun for any other use.

[Honda Hansel]

Yes grease gun (only time i get to use a GUN)works good
made a fitting for the banjo bolt .Out of a old brake hose

Honda Hansel

[Kelly E]

Yes grease gun (only time i get to use a GUN)works good
made a fitting for the banjo bolt .Out of a old brake hose

Honda Hansel

Good idea, I usually pump the pistons out before I disassemble the brake system if it is still working. But sometimes it's too late for that.

Did you have to tap the fitting as is or drill it out before tapping?

[newday777]

Yes grease gun (only time i get to use a GUN)works good
made a fitting for the banjo bolt .Out of a old brake hose

Honda Hansel

I like the hac👍

[RAFster122s]

The thread pitch is a bit different on the grease gun hose for the caliper body. It is close enough, you just screw it in finger tight and pump away. Since you aren't forcing it you get a tiny bit of grease escaping at the connection and sometimes it stops after a bit. Point is it put bulk of material in the caliper body forcing the piston out. You then scoop out the plug if grease after removing the piston and wipe it out, then use brake cleaner to wash out the rest of the grease...

Very easy method. You can separate the contaminated grease from that which is fine and store it for when you need to put a bit of grease on something externally, bolt threads, pivot points, etc. or toss it.
Replace your caliper seals and the caliper piston and clean the caliper seal groove so it is spotless.

[willbird]

The thread pitch is a bit different on the grease gun hose for the caliper body. It is close enough, you just screw it in finger tight and pump away. Since you aren't forcing it you get a tiny bit of grease escaping at the connection and sometimes it stops after a bit. Point is it put bulk of material in the caliper body forcing the piston out. You then scoop out the plug if grease after removing the piston and wipe it out, then use brake cleaner to wash out the rest of the grease...

Very easy method. You can separate the contaminated grease from that which is fine and store it for when you need to put a bit of grease on something externally, bolt threads, pivot points, etc. or toss it.
Replace your caliper seals and the caliper piston and clean the caliper seal groove so it is spotless.

NAPA had an adapter in their little box of brass adapters behind the counter from the CB750K brake line connection to female NPT.

Bill

[ZingZing]

Looking at the head there is no 392 stamped in the middle of the intake side just an X7. The pistons have 392 stamped on them so the bottom end is probably all F but the head is not, unless some F's don't have 392 on them?

It has exhaust studs but those could've always been swapped. Do the stamp codes have a meaning other than to differentiate the heads, or just 70s Honda quirkiness.

Anyways, I did a leak test on the valves and cylinders 2 and 4 were fine but 1 and 3 are leaking with the majority from Exhaust 1 and Intake 3.

I need a cam, rockers, rocker, shaft, and rocker towers for sure so at that point if this isn't a 75-76 F head I might as well source a whole F head to swap.

And any tips on removing valve guides and seals? I got the valve, springs, and top retaining pieces out, but if the guides don't have any play and the valve doesn't have too much wear then I wouldn't need to change out the guides, just the seals? Head isn't clean yet and I saw some posts about not moving the guides to avoid dragging carbon through the bore so maybe removing the guides isn't possible at this time.

[willbird]

I would not be driving the valve guides out ?? If they are removed or changed they will no longer be concentric to the valve seats...then the valve seats need ground. I'd leave that to whoever does your valve grind.

[Jerry Rxman Griffin aka MuthaF'er]

Post a picture of the combustion chambers of the head. The K heads are distinctly different as far as the shapes of the chambers. Perhaps you have a 392 head without the 392 marking. The 2 pictures you posted can not be opened on my end and I can't see anything that tells me something

[willbird]

Post a picture of the combustion chambers of the head. The K heads are distinctly different as far as the shapes of the chambers. Perhaps you have a 392 head without the 392 marking. The 2 pictures you posted can not be opened on my end and I can't see anything that tells me something

His bike is an F1 ? Are things as drastically different with the F1 ? I have a head I bought from ebay years ago, it was billed as an F head, has studs but is not a 392 casting. Late K are a 392 casting ??

[Jerry Rxman Griffin aka MuthaF'er]

Yes, he has a 76 F which is a F1. The first 392 head appeared in the 75 F. The 'shrouds" by the plug hole from the earlier K's were eliminated and it appears as more of a smooth dished hemi shape but obviously not half round hemi style. It continued to the 76 F and was adopted for the 77 and 78 K engines. Can't say about the A's though? It is not as drastically different as the 77/78 F head with somewhat oval shaped combustion chamber for the big intake valves and the valve angle difference that is blamed for the valve guide wear issue. The 77/78 head came from Honda painted black but any head can be painted black after the fact. Both of my 392 heads are NOW black. The 77/78 F head also has less oil return holes.   

[scottly]

My K7 head doesn't have the 392 marking, either.

[Jerry Rxman Griffin aka MuthaF'er]

Looks like a 392 to me

[ZingZing]

Combustion chambers - https://imgur.com/a/tEgFTPG

Previous head pics - https://imgur.com/a/comxTrs


Let me know if these are showing up.