Topic: 1971 CB750 K1 Restoration Project- Restoring Still...

[PeWe]

I have replaced pump several times with my CB750 on side stand. 2 times for priming it (again) due to air trapped inside.
(Last time due to I removed the spring , piston with rubber I replaced due to wet sumping, oil in tank leaked thru the pump when parked. Air entered when oil went out the short time it took to do the rubber swap. Had to remove pump and prime it in a container with oil.)

If stock 4-4, remove pipes for cyl 3-4.
I had to remove my 4-2-1 on my K6 completely since it cover the oil pan

I used my phone selfie cam to inspect the pump and everything else. Remove  eventual  gasket residues. A pain if a sealer has been used before with residues on gasket surface.

Honda stock gasket (light green) the best alternative I have tried.
Holes where they should and a have  nice surface.
Oilpan can be removed several times without replacing the gasket. Same with other covers when using Honda gaskets

I was laying down on my back when I was installing the carefully primed pump. Then I saw how to fit it.

Priming:
You have to rotate the pump sprocket with the relieve valve open to let air bubbles out when priming. The big alu nut removed or at least almost off with spring and piston inside.

Stock spring better than eventual oil pump kit replacement spring. I got 70PSI when cold with shiny replacement spring when cold at idle. 80PSI with old stock.

Rotate sprocket with pump submerged in oil, cover one hole with finger. You'll feel how it will suck. If not, cover the other hole. Rotate in other direction and feel the underpressure.
If you can not feel this, pump has air and will not work. No oil pressure when running engine on starter without sparkplugs.

The 3 new o-rings and knock pins must sit. Easier to have some oil on them.  You'll see which is best, knock pin sit in case or pump. O-rings are important. I did both....

The pump must go on absolutely parallel to engine to avoid damaged knock pins or alu scratched off.

There is a reason why I have ca 10 new knock pins as spare

Worst first time....

[MauiK3]

That first time learning can be painful but after that, all good :-))

[Oly]

John, Maui and Per....Thanks for your valued input on the subject!

   I'll be leaving it off till engine is back in and bike is back on it's feet with the capability to spin the engine w/out plugs to confirm pressure buildup.

[Oly]

After researching the forum for methods to disassemble front caliper assembly, I used the grease gun process to press out the pad, piston and seal.  Even though there were only a couple threads engaged from the grease gun to the caliper assembly it worked like a charm.  Thanks to the forum population for the insight into how to tackle this task.

Also received the new clutch lifter plate to replace the original that had a hairline crack in it.

I got a photo of a modified CB750 in the back of a pickup, but wasn't able to find the owner to ask any questions.

[Oly]

After 10 weeks on the mend for a broken right index finger with torn tendon I'm finally back on the project to get the rebuilt head (new valves/guides & recut seats) and cylinders bored +.50mm assembled.

I do have a question for the forum related to the 8 additional oiling holes in the cam towers described in Hondaman's book.
Of the people who have drilled these additional holes how many have found this to be a benefit (increased longevity or decreased noise in the rocker assembly, etc)?  I see where this might be good if you are running the engine at constant high revs, as in racing, but is it worth it if it is a stock bike with normal use.
My bike has 30K on the original engine and I was only thinking about doing it if it might help the rocker assemblies last longer.

Thoughts?

[HondaMan]

After 10 weeks on the mend for a broken right index finger with torn tendon I'm finally back on the project to get the rebuilt head (new valves/guides & recut seats) and cylinders bored +.50mm assembled.

I do have a question for the forum related to the 8 additional oiling holes in the cam towers described in Hondaman's book.
Of the people who have drilled these additional holes how many have found this to be a benefit (increased longevity or decreased noise in the rocker assembly, etc)?  I see where this might be good if you are running the engine at constant high revs, as in racing, but is it worth it if it is a stock bike with normal use.
My bike has 30K on the original engine and I was only thinking about doing it if it might help the rocker assemblies last longer.

Thoughts?

You're spot-on about their purpose and use: that was done for bikes raced at high engine speeds, like pushing 10k RPM with larger carbs (mostly the ones from the 750 "racing kit", in roadracing environs. It helped prevent the galling of the rocker shafts inside the rocker towers, which caused them to get stuck after a while, making teardowns harder (if not ruining the cam bearings altogether). For normal street use: I did the holes to my K2 in 1980 because the rocker shafts were showing some wear at 50k miles when I had the engine apart: the rocker shafts were fine, but the holes in the cam bearings were getting larger by almost 0.001". When I again tore it down in 2006 at 121k miles those holes had not grown any further, which I thought was interesting. I ran those shafts and bearings until 2013 when I rebuilt the whole engine at 136k miles. At that time the cam bearings at the journals were showing enough wear that I replaced them. I didn't drill the extra holes into the new bearings then, but I did leave the 5mm bolts out.

Starting in 1973 Honda bolted these rocker shafts down in response to the DOT requiring the bikes to be "quieter" in the [unique] drive-by test that consisted of running past a microphone that was 3 feet away, at redline RPM in 2nd gear, then measuring that noise level (all bikes had to pass this test). It could not exceed 82dbA, which corresponded to real-life numbers like 85dB on a normal logarithmic scale. Several other mods were also applied: a couple of them were the [in]famous 7-chamber HM341 mufflers (which went to 5-chamber quickly & quietly for rust troubles in late Fall of 1973) instead of the 4 chambers of the K2 version of the pipes, and the intake slots in the airbox received a higher 'dam' on the inner side, making the inlets smaller and slightly less noisy from intake noise at redline speeds. Both of these items reduced performance in the K3 bikes as compared to the K2.

When the US DOT notched this "noise level" down again (80dbA) for the 1975 model year, Honda went to the extra-quiet (and extra-restrictive) 4-1 pipe set for the 750F0. A lawsuit against the government (interestingly brought by Harley Davidson) over this new noise level got that notch-down stopped in the winter of 1975-76, and the later 750F1 4-1 exhaust worked better, if being slightly noisier at redline.

[Oly]

Thanks Mark...always appreciate your input from a lifetime of hands on experience.  When you performed the drilling of these 8 additional holes in 1980 were you able to perform this freehand or did you do it on a drill press?  You know my top end well from doing the rebuild, so would you recommend I place these additional holes in the towers or wait until I have higher miles on rocker assembly?

[HondaMan]

Thanks Mark...always appreciate your input from a lifetime of hands on experience.  When you performed the drilling of these 8 additional holes in 1980 were you able to perform this freehand or did you do it on a drill press?  You know my top end well from doing the rebuild, so would you recommend I place these additional holes in the towers or wait until I have higher miles on rocker assembly?

While I've drilled them on a mill, a drill press and freehand, it was also on racing engines (except mine), or on request a few times by owners of engines I was rebuilding. If you centerpunch those little circles beforehand and are doing it by hand, just start with a small drill bit first, like smaller than 1/8" for starters. It's not like you can do them 'wrong' because the oil will always find its way to the shaft, whether on the top or along the side, as they fill up from splash oiling while running. The first ones I encountered in 1970 were done along the sides of the shafts, because the owner believed the shafts spun while in operation and that would help "feed" the oil. How he determined that still puzzles me, though, because the shaft's operation is reciprocal, back-and-forth?

But, he WAS a good rider and did well on the track near Peoria, which got my attention at the time.

[scottly]

I see where this might be good if you are running the engine at constant high revs, as in racing, but is it worth it if it is a stock bike with normal use.
My bike has 30K on the original engine and I was only thinking about doing it if it might help the rocker assemblies last longer.

Thoughts?

It's not necessary at all, IMHO, and certainly not worth tearing into a low mileage engine for.

[Oly]

I see where this might be good if you are running the engine at constant high revs, as in racing, but is it worth it if it is a stock bike with normal use.
My bike has 30K on the original engine and I was only thinking about doing it if it might help the rocker assemblies last longer.

Thoughts?

It's not necessary at all, IMHO, and certainly not worth tearing into a low mileage engine for.

Totally agree Scott...thanks for the feedback. 
Doesn't seem like a thing that a lot of people routinely do and is probably much more applicable for engines used for racing and running on the ragged edge, which is not going to be my usage.

[Oly]

After reading a thread started by Stu I realized my disassembly of the Carb Rack shaft to replace a broken throttle cable attach point assembly was going to be easier than I realized because of the two different types of shaft retention  mechanism.  One with a pressed pin shaft retention and the other a cap with screw & lock washer underneath it for shaft retention.  It was easy to drill a very small hole on the edge of the cap and pop it off to expose the screw/washer which easily came out.  This allowed removal of all the individual components for cleaning, repair and lubrication.

[newday777]

Very fortuitous for each of us

[Oly]

Took Per's (Pee Wee) advise and JB Weld the Cam tower thru bolt holes.
 As soon as this cures I'm starting the process of assembling the rebuilt top end.

[Oly]

Does anybody have a source for rebuilding these Mulholland shocks I had installed on my bike 30 plus years ago?

[BenelliSEI]

Does anybody have a source for rebuilding these Mulholland shocks I had installed on my bike 30 plus years ago?

In my experience, if you “send them out” it costs more than a new set. My last set of Koni’s I carefully dismantled, cleaned and reassembled with fresh oil. They don’t leak and seem to work just fine…….

[Oly]

John... what shocks are you running on your K1 and did you buy them new?