Topic: Restoring my K0 engine

[jebon]

Aye.
Someone has been in there before you: now you might find several other 'surprises'. A common one: the spring washer that holds the clutch housing onto the mainshaft may be backward (which makes for noisy, clunky shifting), the oil port on the left side of the engine, next to the countershaft bearing housing, may be gone, incorrect clutch plates might be installed (and boy, do I have a long list of other things I have seen!).

My favorite: on a CB750K5 that had just been ridden from Michigan to California (and came by here for me to see it and install a Transistor Ignition halfway thru his trip) was later sent to me for a full rebuild. It was actually MISSING its oil jets in the head! Yet it ran perfectly, the bottom end bearings were in excellent condition, no harm could be found anywhere inside. And the cam and rockers were gorgeous. The cam cover had been extra-sealed with some black goo, though, which probably was needed with the extra-deep oil it was getting!

Thanks! I've tackled the outer part of the clutch which was only half assembled Will keep my eyes open. BTW do you have any more of those "correct" size O-rings that go with new gasket sets? I'm thinking of getting a set from CycleX. Do you know if I'll need other O-rings for that?

[jebon]

Aye.
Someone has been in there before you: now you might find several other 'surprises'. A common one: the spring washer that holds the clutch housing onto the mainshaft may be backward (which makes for noisy, clunky shifting), the oil port on the left side of the engine, next to the countershaft bearing housing, may be gone, incorrect clutch plates might be installed (and boy, do I have a long list of other things I have seen!).

My favorite: on a CB750K5 that had just been ridden from Michigan to California (and came by here for me to see it and install a Transistor Ignition halfway thru his trip) was later sent to me for a full rebuild. It was actually MISSING its oil jets in the head! Yet it ran perfectly, the bottom end bearings were in excellent condition, no harm could be found anywhere inside. And the cam and rockers were gorgeous. The cam cover had been extra-sealed with some black goo, though, which probably was needed with the extra-deep oil it was getting!

This one right? (image from Hackaweek video)
BTW just ordered your book. Can't wait to get it

[HondaMan]

Aye.
Someone has been in there before you: now you might find several other 'surprises'. A common one: the spring washer that holds the clutch housing onto the mainshaft may be backward (which makes for noisy, clunky shifting), the oil port on the left side of the engine, next to the countershaft bearing housing, may be gone, incorrect clutch plates might be installed (and boy, do I have a long list of other things I have seen!).

My favorite: on a CB750K5 that had just been ridden from Michigan to California (and came by here for me to see it and install a Transistor Ignition halfway thru his trip) was later sent to me for a full rebuild. It was actually MISSING its oil jets in the head! Yet it ran perfectly, the bottom end bearings were in excellent condition, no harm could be found anywhere inside. And the cam and rockers were gorgeous. The cam cover had been extra-sealed with some black goo, though, which probably was needed with the extra-deep oil it was getting!

This one right? (image from Hackaweek video)
BTW just ordered your book. Can't wait to get it

Yep, that's the one! The curved part goes toward YOU, not the engine, when it's installed. This makes it act like a shock absorber, holding the clutch to the mainshaft. Honda used to spec a torque for it, but that number seems to be lost now. When you tighten it you will feel it getting tighter and still turning, then stops if you go too far. If it goes that far, back it off about 1/4 turn, then turn it back in to the first locktab that will line up. This will leave it some slight springiness to absorb the more severe road shocks (like burnouts...) that can actually flex the mainshaft a bit. This shaft twists under heavy throttle (or severe road shocks to the frame) and correspondingly shrinks-grows-shrinks until the recoil wears itself out. This slight flexible movement helps to absorb it all.

[PeWe]

OK, the clutch center nut should also be tightened by feel, not only a torque like 45Nm?
The spring function of that washer is an important detail.

I'll check that next time.

[38rudge]

Chances are very high that the valves are leaking and it needs at least a step-bore and you can get genuine Honda cam chain tensioner and chain parts from either Sound Sound Honda or JTMarks at eBay. When you talk with your "reputable shop", ask them one VERY pointed question: "What piston clearance will you use?". If they tell you anything more than 0.001" (that's one thousandths of an inch - it should actually be less than that...), then go find another shop, or you WILL end up right where you are now in less than 5000 miles, if that far. Almost half of the engines I receive for rebuild now were butchered by some "reputable shop" or another - which is why I wrote that book that MauiK3 mentioned.

When you quote 1" thou clearance is that the total, 0.5" thou per side or 1" thou per side?

[jebon]

Chances are very high that the valves are leaking and it needs at least a step-bore and you can get genuine Honda cam chain tensioner and chain parts from either Sound Sound Honda or JTMarks at eBay. When you talk with your "reputable shop", ask them one VERY pointed question: "What piston clearance will you use?". If they tell you anything more than 0.001" (that's one thousandths of an inch - it should actually be less than that...), then go find another shop, or you WILL end up right where you are now in less than 5000 miles, if that far. Almost half of the engines I receive for rebuild now were butchered by some "reputable shop" or another - which is why I wrote that book that MauiK3 mentioned.

Now I can't help thinking about a 836 kit. Is this just a matter of getting the pistons and boring it up? Will I need to do anything else?

[HondaMan]

Chances are very high that the valves are leaking and it needs at least a step-bore and you can get genuine Honda cam chain tensioner and chain parts from either Sound Sound Honda or JTMarks at eBay. When you talk with your "reputable shop", ask them one VERY pointed question: "What piston clearance will you use?". If they tell you anything more than 0.001" (that's one thousandths of an inch - it should actually be less than that...), then go find another shop, or you WILL end up right where you are now in less than 5000 miles, if that far. Almost half of the engines I receive for rebuild now were butchered by some "reputable shop" or another - which is why I wrote that book that MauiK3 mentioned.

Now I can't help thinking about a 836 kit. Is this just a matter of getting the pistons and boring it up? Will I need to do anything else?

DON'T use forged pistons. Use something like the CruisinImage kit if you're going big-bore. Those are cast pistons that much more closely match the thermal design of the OEM pistons.

That said: the big-bore kit will bring you about 8 HP more than you have now, but much of that will also ebb away in about 5000-8000 miles as the cylinders will warp again, like they did when new. If you step-bore it instead, like 0.5mm or maybe 1.00mm, you will gain 5-6 HP more than when it came apart, but it will STAY there, essentially forever, because the cylinders are now cured and stable for about 1.5mm-2.0mm deep. This is a natural characteristic of the kinds of metals used in these engines.

[HondaMan]

Chances are very high that the valves are leaking and it needs at least a step-bore and you can get genuine Honda cam chain tensioner and chain parts from either Sound Sound Honda or JTMarks at eBay. When you talk with your "reputable shop", ask them one VERY pointed question: "What piston clearance will you use?". If they tell you anything more than 0.001" (that's one thousandths of an inch - it should actually be less than that...), then go find another shop, or you WILL end up right where you are now in less than 5000 miles, if that far. Almost half of the engines I receive for rebuild now were butchered by some "reputable shop" or another - which is why I wrote that book that MauiK3 mentioned.

When you quote 1" thou clearance is that the total, 0.5" thou per side or 1" thou per side?

1 thousandths, total. No more.

When I rebuilt my 750 in 2013 I set this at 0.0006" piston clearance, partly because I wanted to see what it would do, and partly because I am sure it won't cause trouble. In the end, my machine shop was real nervous about it until i pointed out that I have been using 0.0004"-0.0006" (like Honda does) on the singles (CB100/125 and CB160 twins). In the end they made me declare that I won't 'hold them responsible' for what happens: so, after the bike runs amazingly cooler, smoother, and has a lot more power than i expected, even when hot, I told them they culdn't take credit for it, either...    Now, they bore their racing engines with 40% less clearance than they used to, too. they are mostly a racing enterprise, but they do good precision work.

When I got mine broken in, it had so much more power that I geared it up another tooth, to a 19T countersprocket, to drop the engine RPM at 80-90 MPH (that's normal interstate speeds out here in the West). It's really nice out on the open road!

[jebon]

Chances are very high that the valves are leaking and it needs at least a step-bore and you can get genuine Honda cam chain tensioner and chain parts from either Sound Sound Honda or JTMarks at eBay. When you talk with your "reputable shop", ask them one VERY pointed question: "What piston clearance will you use?". If they tell you anything more than 0.001" (that's one thousandths of an inch - it should actually be less than that...), then go find another shop, or you WILL end up right where you are now in less than 5000 miles, if that far. Almost half of the engines I receive for rebuild now were butchered by some "reputable shop" or another - which is why I wrote that book that MauiK3 mentioned.

Now I can't help thinking about a 836 kit. Is this just a matter of getting the pistons and boring it up? Will I need to do anything else?

DON'T use forged pistons. Use something like the CruisinImage kit if you're going big-bore. Those are cast pistons that much more closely match the thermal design of the OEM pistons.

That said: the big-bore kit will bring you about 8 HP more than you have now, but much of that will also ebb away in about 5000-8000 miles as the cylinders will warp again, like they did when new. If you step-bore it instead, like 0.5mm or maybe 1.00mm, you will gain 5-6 HP more than when it came apart, but it will STAY there, essentially forever, because the cylinders are now cured and stable for about 1.5mm-2.0mm deep. This is a natural characteristic of the kinds of metals used in these engines.

Thank you. A step bore it'll be then.
Should I still get the cruising image ones?

[jebon]

My exhaust valve guides are of this type but they still had a regular guide seal on them. I believe they didn't originally. Will a seal on this type of guide make any difference? They really puzzled me until I google'd it. I thought some clown had installed new exhaust guides upside down

[PeWe]

No plans using hotter cam, cruzinimage will be fine.
There is a loooooong yhread about those pistons.

I use Cruzinimage K7 61.5mm pistons in my stock K2, work fine. +56whp. It has K7 cam too, not much difference, maybe a little bit "revvier". It likes to rev to +8000rpm. Head has race springs.

[Old Moe Toe]

Aye.
Someone has been in there before you: now you might find several other 'surprises'. A common one: the spring washer that holds the clutch housing onto the mainshaft may be backward (which makes for noisy, clunky shifting), the oil port on the left side of the engine, next to the countershaft bearing housing, may be gone, incorrect clutch plates might be installed (and boy, do I have a long list of other things I have seen!).

My favorite: on a CB750K5 that had just been ridden from Michigan to California (and came by here for me to see it and install a Transistor Ignition halfway thru his trip) was later sent to me for a full rebuild. It was actually MISSING its oil jets in the head! Yet it ran perfectly, the bottom end bearings were in excellent condition, no harm could be found anywhere inside. And the cam and rockers were gorgeous. The cam cover had been extra-sealed with some black goo, though, which probably was needed with the extra-deep oil it was getting!

 It was actually MISSING its oil jets in the head! Yet it ran perfectly, the bottom end bearings were in excellent condition, no harm could be found anywhere inside. And the cam and rockers were gorgeous
 That is very interesting!, especially when you consider how easily those jets can get clogged.
Be interesting to leave them out on purpose to see if if they are just not needed.
Well maybe not on a KO, but on some roughie.

[PeWe]

Interesting what a oil pressure gauge will tell....

[jebon]

Got the cases apart today.
Note to self - remember to remove ALL bolts.

Another part forgotten when last opened.
Inner ring on final drive.

Clutch nut turned out to be a real pain. Have not been able to remove it yet. It does seem like the washer behind is flipped too. The guy who assembled this did not intend to have it opened again.
IT IS STUCK!

[HondaMan]

My exhaust valve guides are of this type but they still had a regular guide seal on them. I believe they didn't originally. Will a seal on this type of guide make any difference? They really puzzled me until I google'd it. I thought some clown had installed new exhaust guides upside down

Those type of guides don't use valve seals, so someone was in there before you who did not know what they were doing....if I had $5 for every one of these 750s I've seen like that, I could retire now...

Check for valve guide wear. If the guides are original Stellite, there will not be much, if any, wear: it took 138,000 miles for mine to even approach the wear limits. BUT...if that 'someone' who was in there before you also changed the valve guides, they will not be Stellite, but simple cast iron. If you can be 90% (or more) diligent to add an ounce or 2 of 2-stroke oil to every tank of gasoline you use, they will last a while (maybe 25k miles), but if not, it's time for new, bronze, valve guides. I recommend APE's guides as the ones I use most, unless you have enough $$ to use the Kibblewhite type. The Kibblewhite are made of harder bronze (so I have heard), but the APE will likely last 100,000 miles anyway.

[HondaMan]

Aye.
Someone has been in there before you: now you might find several other 'surprises'. A common one: the spring washer that holds the clutch housing onto the mainshaft may be backward (which makes for noisy, clunky shifting), the oil port on the left side of the engine, next to the countershaft bearing housing, may be gone, incorrect clutch plates might be installed (and boy, do I have a long list of other things I have seen!).

My favorite: on a CB750K5 that had just been ridden from Michigan to California (and came by here for me to see it and install a Transistor Ignition halfway thru his trip) was later sent to me for a full rebuild. It was actually MISSING its oil jets in the head! Yet it ran perfectly, the bottom end bearings were in excellent condition, no harm could be found anywhere inside. And the cam and rockers were gorgeous. The cam cover had been extra-sealed with some black goo, though, which probably was needed with the extra-deep oil it was getting!

 It was actually MISSING its oil jets in the head! Yet it ran perfectly, the bottom end bearings were in excellent condition, no harm could be found anywhere inside. And the cam and rockers were gorgeous
 That is very interesting!, especially when you consider how easily those jets can get clogged.
Be interesting to leave them out on purpose to see if if they are just not needed.
Well maybe not on a KO, but on some roughie.

This has led me to increase the oil hole size by 0.002" on some of these engines when I have them apart, like the Megacycle-cammed ones where the engine may well find itself in redline terrain more often.

[HondaMan]

Got the cases apart today.
Note to self - remember to remove ALL bolts.

Another part forgotten when last opened.
Inner ring on final drive.

Clutch nut turned out to be a real pain. Have not been able to remove it yet. It does seem like the washer behind is flipped too. The guy who assembled this did not intend to have it opened again.
IS IT STUCK!

One of the things that can happen when the cupped washer gets flipped over is: the edges, over time, will dig into the fancy nut's slots, locking it in but good. Not to worry: while you might have to buy the clutch-nut-remover tool (Motion Pro sells them, so does PartsNmore from time to time, or CB750Supply), you can also get a new clutch nut and washer (and I have both if you can't find them, but used). If you can't find that halaf-moon retaining clip for the final-drive inner bearing, I have some of those, too, from engines that could not be otherwise saved. The later engines don't have that inner retaining half-ring, but have a different, 2-ball-row bearing on the outer one to make up the rigidity.

[jebon]

Aye.
Someone has been in there before you: now you might find several other 'surprises'. A common one: the spring washer that holds the clutch housing onto the mainshaft may be backward (which makes for noisy, clunky shifting), the oil port on the left side of the engine, next to the countershaft bearing housing, may be gone, incorrect clutch plates might be installed (and boy, do I have a long list of other things I have seen!).

My favorite: on a CB750K5 that had just been ridden from Michigan to California (and came by here for me to see it and install a Transistor Ignition halfway thru his trip) was later sent to me for a full rebuild. It was actually MISSING its oil jets in the head! Yet it ran perfectly, the bottom end bearings were in excellent condition, no harm could be found anywhere inside. And the cam and rockers were gorgeous. The cam cover had been extra-sealed with some black goo, though, which probably was needed with the extra-deep oil it was getting!

This one right? (image from Hackaweek video)
BTW just ordered your book. Can't wait to get it

Yep, that's the one! The curved part goes toward YOU, not the engine, when it's installed. This makes it act like a shock absorber, holding the clutch to the mainshaft. Honda used to spec a torque for it, but that number seems to be lost now. When you tighten it you will feel it getting tighter and still turning, then stops if you go too far. If it goes that far, back it off about 1/4 turn, then turn it back in to the first locktab that will line up. This will leave it some slight springiness to absorb the more severe road shocks (like burnouts...) that can actually flex the mainshaft a bit. This shaft twists under heavy throttle (or severe road shocks to the frame) and correspondingly shrinks-grows-shrinks until the recoil wears itself out. This slight flexible movement helps to absorb it all.

Just getting to the clutch now. This sounds like it's nowhere near 45nm. More like 20 or 30?

[HondaMan]

Look closely to see if the lock tab from the locking washer is holding that nut locked? It bends up into one of the recess slots to lock the nut.

[Rosinante]

South Sound Honda of Olympia Washington is where Mark was referring to above...

Why South Sound Honda?  The opening poster appears to be in Denmark.  Part of the reason i ask is because I live about equidistant from the Oly and Lakewood South Sound Honda stores.  Are they particularly good at stocking parts for these bikes?

[RAFster122s]

They offer discount parts prices. Look it up on their website and comparison shop with other dealers/suppliers.

If it is orderable from Honda, they will add it to their order and get it for you and ship it to you at a reasonable price.