Topic: From Rundown & Ragged.. To A Mean, Clean & Shiny Machine - My 1977 Honda CB750 K

[Ellz10]

Here is a screenshot of the exact same setup as my countershaft assembly (this is a shot from a video I watched). Notice his doesn't have a thrust washer before C2 nor after C3, just like I mentioned mine doesn't.

Mark's book shows there being thrust washers there. The parts fiche for 1977 show that as well, so what's the deal?

[HondaMan]

Hmm...by chance, does your C3 gear have a cast-iron, flanged insert that fits into the center of the gear? If so, the flanged side of it acts as the separate toothed washer-bushing, and this side of it should be set against the circlip. This was found in some 750F3 engines.

The picture in the book was taken as I tore down a 750F0 engine (the same one shown in the "Remove Engine" chapter). In the late F2, and I have also seen in the K8, the bronze bushings and center bearings were sometimes replaced with flanged cast-iron versions, eliminating the separate bronze toothed washer.
Gammaflat knows something about that one...   ). In those cases, the flange of the flanged bushing sat against the circlip, instead of the separate toothed washer.

[Ellz10]

Hmm...by chance, does your C3 gear have a cast-iron, flanged insert that fits into the center of the gear? If so, the flanged side of it acts as the separate toothed washer-bushing, and this side of it should be set against the circlip. This was found in some 750F3 engines.

The picture in the book was taken as I tore down a 750F0 engine (the same one shown in the "Remove Engine" chapter). In the late F2, and I have also seen in the K8, the bronze bushings and center bearings were sometimes replaced with flanged cast-iron versions, eliminating the separate bronze toothed washer.
Gammaflat knows something about that one...   ). In those cases, the flange of the flanged bushing sat against the circlip, instead of the separate toothed washer.

Okayyyy, now I'm getting somewhere! Thank you Mark!

So yes, both my C2 and C3 gears have the flanged bushing/insert.

Now the next question becomes this: does the flat side of the circlip point towards the flange of that insert? Or does the chamfered side of the circlip point towards the flange of that insert?

[HondaMan]

Hmm...by chance, does your C3 gear have a cast-iron, flanged insert that fits into the center of the gear? If so, the flanged side of it acts as the separate toothed washer-bushing, and this side of it should be set against the circlip. This was found in some 750F3 engines.

The picture in the book was taken as I tore down a 750F0 engine (the same one shown in the "Remove Engine" chapter). In the late F2, and I have also seen in the K8, the bronze bushings and center bearings were sometimes replaced with flanged cast-iron versions, eliminating the separate bronze toothed washer.
Gammaflat knows something about that one...   ). In those cases, the flange of the flanged bushing sat against the circlip, instead of the separate toothed washer.

Okayyyy, now I'm getting somewhere! Thank you Mark!

So yes, both my C2 and C3 gears have the flanged bushing/insert.

Now the next question becomes this: does the flat side of the circlip point towards the flange of that insert? Or does the chamfered side of the circlip point towards the flange of that insert?

There, NOW you've got it!
The flanged side of that iron bushing takes the place of the bronze toothed washer, so flip that one 'round and you should be on your way!
I would estimate that to be a K8 gearbox.

[Ellz10]

Hmm...by chance, does your C3 gear have a cast-iron, flanged insert that fits into the center of the gear? If so, the flanged side of it acts as the separate toothed washer-bushing, and this side of it should be set against the circlip. This was found in some 750F3 engines.

The picture in the book was taken as I tore down a 750F0 engine (the same one shown in the "Remove Engine" chapter). In the late F2, and I have also seen in the K8, the bronze bushings and center bearings were sometimes replaced with flanged cast-iron versions, eliminating the separate bronze toothed washer.
Gammaflat knows something about that one...   ). In those cases, the flange of the flanged bushing sat against the circlip, instead of the separate toothed washer.

Okayyyy, now I'm getting somewhere! Thank you Mark!

So yes, both my C2 and C3 gears have the flanged bushing/insert.

Now the next question becomes this: does the flat side of the circlip point towards the flange of that insert? Or does the chamfered side of the circlip point towards the flange of that insert?

There, NOW you've got it!
The flanged side of that iron bushing takes the place of the bronze toothed washer, so flip that one 'round and you should be on your way!
I would estimate that to be a K8 gearbox.

Ugh, Mark you didn't answer the question I need the answer to!

I need to know about the circlip.

Does the flat side of the circlip point towards the flange of that insert? Or does the chamfered side of the circlip point towards the flange of that insert?

[HondaMan]

Hmm...by chance, does your C3 gear have a cast-iron, flanged insert that fits into the center of the gear? If so, the flanged side of it acts as the separate toothed washer-bushing, and this side of it should be set against the circlip. This was found in some 750F3 engines.

The picture in the book was taken as I tore down a 750F0 engine (the same one shown in the "Remove Engine" chapter). In the late F2, and I have also seen in the K8, the bronze bushings and center bearings were sometimes replaced with flanged cast-iron versions, eliminating the separate bronze toothed washer.
Gammaflat knows something about that one...   ). In those cases, the flange of the flanged bushing sat against the circlip, instead of the separate toothed washer.

Okayyyy, now I'm getting somewhere! Thank you Mark!

So yes, both my C2 and C3 gears have the flanged bushing/insert.

Now the next question becomes this: does the flat side of the circlip point towards the flange of that insert? Or does the chamfered side of the circlip point towards the flange of that insert?

There, NOW you've got it!
The flanged side of that iron bushing takes the place of the bronze toothed washer, so flip that one 'round and you should be on your way!
I would estimate that to be a K8 gearbox.

Ugh, Mark you didn't answer the question I need the answer to!

I need to know about the circlip.

Does the flat side of the circlip point towards the flange of that insert? Or does the chamfered side of the circlip point towards the flange of that insert?

Chamfered side to the bushing, absolutely! The 'straight' side of it does not let oil leak in between this clip's face and the bushing, which is needed to help keep the clip cooler than the bushing so it won't try to 'climb' or warp, and move.

You'll note that the gear next to it on the clip's side (C2) stops about 2mm away from the clip when the shift fork moves it in that direction, too.

[Ellz10]

Hmm...by chance, does your C3 gear have a cast-iron, flanged insert that fits into the center of the gear? If so, the flanged side of it acts as the separate toothed washer-bushing, and this side of it should be set against the circlip. This was found in some 750F3 engines.

The picture in the book was taken as I tore down a 750F0 engine (the same one shown in the "Remove Engine" chapter). In the late F2, and I have also seen in the K8, the bronze bushings and center bearings were sometimes replaced with flanged cast-iron versions, eliminating the separate bronze toothed washer.
Gammaflat knows something about that one...   ). In those cases, the flange of the flanged bushing sat against the circlip, instead of the separate toothed washer.

Okayyyy, now I'm getting somewhere! Thank you Mark!

So yes, both my C2 and C3 gears have the flanged bushing/insert.

Now the next question becomes this: does the flat side of the circlip point towards the flange of that insert? Or does the chamfered side of the circlip point towards the flange of that insert?

There, NOW you've got it!
The flanged side of that iron bushing takes the place of the bronze toothed washer, so flip that one 'round and you should be on your way!
I would estimate that to be a K8 gearbox.

Ugh, Mark you didn't answer the question I need the answer to!

I need to know about the circlip.

Does the flat side of the circlip point towards the flange of that insert? Or does the chamfered side of the circlip point towards the flange of that insert?

Chamfered side to the bushing, absolutely! The 'straight' side of it does not let oil leak in between this clip's face and the bushing, which is needed to help keep the clip cooler than the bushing so it won't try to 'climb' or warp, and move.

You'll note that the gear next to it on the clip's side (C2) stops about 2mm away from the clip when the shift fork moves it in that direction, too.

Awesome thank you! Exactly what I needed to hear, because my thoughts were to install it the exact opposite!

My next question...

The circlip that comes after C4 (going towards C1), what is the orientation for that circlip? Does the flat side of the circlip point towards C4 or does the chamfered side of the circlip point towards C4?

Same goes for the thrust washer - does the flat side point towards C4 or does the chamfered side point towards C4?

[HondaMan]

Hmm...by chance, does your C3 gear have a cast-iron, flanged insert that fits into the center of the gear? If so, the flanged side of it acts as the separate toothed washer-bushing, and this side of it should be set against the circlip. This was found in some 750F3 engines.

The picture in the book was taken as I tore down a 750F0 engine (the same one shown in the "Remove Engine" chapter). In the late F2, and I have also seen in the K8, the bronze bushings and center bearings were sometimes replaced with flanged cast-iron versions, eliminating the separate bronze toothed washer.
Gammaflat knows something about that one...   ). In those cases, the flange of the flanged bushing sat against the circlip, instead of the separate toothed washer.

Okayyyy, now I'm getting somewhere! Thank you Mark!

So yes, both my C2 and C3 gears have the flanged bushing/insert.

Now the next question becomes this: does the flat side of the circlip point towards the flange of that insert? Or does the chamfered side of the circlip point towards the flange of that insert?

There, NOW you've got it!
The flanged side of that iron bushing takes the place of the bronze toothed washer, so flip that one 'round and you should be on your way!
I would estimate that to be a K8 gearbox.

Ugh, Mark you didn't answer the question I need the answer to!

I need to know about the circlip.

Does the flat side of the circlip point towards the flange of that insert? Or does the chamfered side of the circlip point towards the flange of that insert?

Chamfered side to the bushing, absolutely! The 'straight' side of it does not let oil leak in between this clip's face and the bushing, which is needed to help keep the clip cooler than the bushing so it won't try to 'climb' or warp, and move.

You'll note that the gear next to it on the clip's side (C2) stops about 2mm away from the clip when the shift fork moves it in that direction, too.

Awesome thank you! Exactly what I needed to hear, because my thoughts were to install it the exact opposite!

My next question...

The circlip that comes after C4 (going towards C1), what is the orientation for that circlip? Does the flat side of the circlip point towards C4 or does the chamfered side of the circlip point towards C4?

Same goes for the thrust washer - does the flat side point towards C4 or does the chamfered side point towards C4?

For this one: the chamfered (rounded) side of the clip goes toward the thrust washer, because it can wiggle a bit when the gear next to it is spinning and a shift to it occurs. When you get this shaft back into the crankcase and the forks engaged you'll find that the sliding C4 doesn't quite press up against this clip when in actual use, or if it does, just barely. Since it can't rotate, it doesn't pose any troubles like trying to 'unwind' the clip out of the groove.

The rounded side of that bronze thrust washer should go toward the C1 gear/bushing here, because the bushing in this gear is smaller diameter than the thrust washer - plus, they wiggle against each other some. The 'philosophy' here is: (after 200,000 miles or so, maybe?) that thrust washer might gall against the bushing inside the gear if the flat side was there, so a trifle more oil will work its way into that joint if the rounded side is pressed up against it.

The caveat here, in the later engines, is: this bushing was often made of cast iron, or included into the C1's inner bushing as a flanged bushing when it was made from cast iron (I have seen it both ways), so then the oil (and rounded side) needed to be in between the circlip and the bushing face, lest it friction-weld itself to the clip over time (only a long roadrace could accomplish it, but Honda was uber-conservative in those days). I know of just one guy (in Colorado)_ who worried enough about this with his 750F2 racer that he hand-lapped both sides of both the circlip and the (in his) cast-iron thrust washer for 'better oiling'. After we talked about it, he just bought bronze bushing and thrust washer and replaced them, instead - the bronze is a MUCH better bearing on steel, especially at speed. The switch to cast iron was done to save a few Yen to help keep the cost of the 750 competitive at the time.

But, all this said and worried about: sometimes these got assembled wrong at Honda! I've seen it in several engines that came to me: our own member Gammaflat had this happen in his (K6, I think it is), and it lifted the clip out of the groove for the C2 gear(!).

[Ellz10]

Thank you Mark!!!!



Probably a stupid question, but I should definitely be using assembly lube when assembling both the mainshaft and countershaft, right?

[HondaMan]

Thank you Mark!!!!



Probably a stupid question, but I should definitely be using assembly lube when assembling both the mainshaft and countershaft, right?

Better yet: dunk them in oil. I dunk the whole countershaft and spin those gears that will spin. Then I let it drain a while (so I don't mess up my floor, mostly!) and put it back into the crankcase.

[Ellz10]

Will definitely be doing that, thanks once again Mark!!


On a separate note, I just noticed this tonight. Somehow the gears were able to chew up a little bit of the inside of the case and it appears to have caused a very small hairline ripple/crack on the outside of the case as well.

Should I have it welded to be safe or let it be as it is?

[Ellz10]

Yes, that needs to be repaired else it will leak oil heavily.

It won’t be fun. And whomever welds it needs to make a jig to bolt the case to for dead perfect alignment when mating the case halves. I’d take a 3/8” piece of aluminum and drill and tap holes through it the case could bolt to. (Imagine a plate that was sandwiched between the halves. Then bolt the repair side to it, then weld it up. Leave it bolted while it cools.

And for welding cat aluminum, have them use 4047 filler. Works best.

Well this sucks. Better that I noticed it though - saves me from having to tear it all back down once again.

I'll take it to the weld shop here and explain what you said and then just hope that they adhere to it and don't mess it up.

Thank you Cal.

[scottly]

Will definitely be doing that, thanks once again Mark!!


On a separate note, I just noticed this tonight. Somehow the gears were able to chew up a little bit of the inside of the case and it appears to have caused a very small hairline ripple/crack on the outside of the case as well.

Should I have it welded to be safe or let it be as it is?

That looks like a big #$%*ing crack in the pic!!?? The misplaced snap-ring on the undercut trans caused a lot of damage to the case as well as the broken gear teeth when it jammed up. I would not recommend just welding up the leaks, or expecting a welder to try to pull the case back into alignment, I would replace the crankcase. The vendor that sold you the trans is at fault for all the damage, IMHO.

[Ellz10]

If you do take it to a shop to be welded, be absolutely certain you don’t clean the cases with anything that has chlorine in it (like Brake Cleaner, Degreasers, etc). Only use Acetone or known non -chlorinated cleaners. The presence of chlorine can kill when welding occurs.

I'll be sure to stick with acetone, thank you!

Will definitely be doing that, thanks once again Mark!!


On a separate note, I just noticed this tonight. Somehow the gears were able to chew up a little bit of the inside of the case and it appears to have caused a very small hairline ripple/crack on the outside of the case as well.

Should I have it welded to be safe or let it be as it is?

That looks like a big #$%*ing crack in the pic!!?? The misplaced snap-ring on the undercut trans caused a lot of damage to the case as well as the broken gear teeth when it jammed up. I would not recommend just welding up the leaks, or expecting a welder to try to pull the case back into alignment, I would replace the crankcase. The vendor that sold you the trans is at fault for all the damage, IMHO.

The crack is a little less than 3/8". Yeah I never expected it to cause this much damage.

Fortunately there weren't any leaks while it was running, nor are the cases out of alignment, thank goodness! So long as the heat from the welding doesn't cause the metal to pull or shrink, I should be alright.

I would absolutely hate to have to buy a new case and then spend even more money boring to 65mm, line lapping the cases, ect.

I'm quite literally tapped of all the money I had saved to do this build and then some extra that the wife doesn't know about.

[scottly]

Fortunately there weren't any leaks while it was running, nor are the cases out of alignment, thank goodness! So long as the heat from the welding doesn't cause the metal to pull or shrink, I should be alright.
The case has already been distorted out of shape. Your bearings don't fit anymore.

I would absolutely hate to have to buy a new case and then spend even more money boring to 65mm, line lapping the cases, ect.
The case doesn't get bored to 65mm, only the cylinders. What are you talking about when you say "line lapping the cases"??

I'm quite literally tapped of all the money I had saved to do this build and then some extra that the wife doesn't know about.
In my opinion, you paid someone big money for sub-standard work that has caused all this damage. He should make this right.

[grcamna2]

Will definitely be doing that, thanks once again Mark!!


On a separate note, I just noticed this tonight. Somehow the gears were able to chew up a little bit of the inside of the case and it appears to have caused a very small hairline ripple/crack on the outside of the case as well.

Should I have it welded to be safe or let it be as it is?

That looks like a big #$%*ing crack in the pic!!?? The misplaced snap-ring on the undercut trans caused a lot of damage to the case as well as the broken gear teeth when it jammed up. I would not recommend just welding up the leaks, or expecting a welder to try to pull the case back into alignment, I would replace the crankcase. The vendor that sold you the trans is at fault for all the damage, IMHO.

+1 on replacing the cases

[Ellz10]

Can you post some different pics of the cases? Those were either too close-up or not enough perspective to appreciate the size of the crack.

Hope these help. The outside crack is quite small and the inside one is more of a deep gouge.

Scott - the only bearing that wasn't fitting ended up being the problem of a worn out countershaft bearing holder. I got a new bearing and new bearing holder and it fits perfectly now!

But I do agree with you to the point of who should be liable, alas he's already stated he's not willing to accept responsibility for it and that's all there is to it unfortunately. Lesson learned for me insofar that I will always inspect someone else's work before installing it into anything I'm personally working on. Expensive lesson learned.

[HondaMan]

I've actually seen K0 near-sandcast cases like that where the "fixer" had finger-wiped JB Weld into the holes on both sides of the case, and rode on. They were caused by debris left in the bottom end following a chain-thru-the-case event, which was also fixed up with JB Weld. The owner rode that bike for years like that, then died of old age and his wife sold it some 10 years later, not knowing the history. I got it for general rebuild and found all the damage, and the new owner wanted it all kept "numbers correct" for his Concours-style resto, so dug/ground/drilled out all the JB Weld and had the holes welded closed, then had the chain hole welded shut, then had the surface of the lower case welded up/milled back (3 times each) until the case would close again, and seal.

No, it wasn't cheap, but then I had Ivo the Magician for my [re]welding and a longtime friend in a local machine shop for the repetitive [re]machining operation to make the cases close up. In the end it works, and has been running about 5 or 6 years, now, no leaks!

After that one, every time I go to Ivo's welding shop he looks sideways at me and asks, "Is this another sandcast engine?".

[Ellz10]

Cal I'm just now reading these posts and I didn't see your DM until today! I had already dropped it off at the shop early yesterday. Wish I would've waited - could've been cheaper for me and I know damn well you'd have done a better job than these folks. I called to see if I could pick it up if they hadn't started working on it yet, but they said they had a guy on it at the moment. So at this point I'll just pray they did it correctly and listened to my pleas asking them to handle the case very carefully so as not to marr any mating surfaces.

I'll let you know how it looks either way with pictures.




Secondly, attached are pictures of the mainshaft that I just disassembled. Mark, maybe you can tell me if the guy installed the circlips correctly. Also attached are pics of M2 and M3 showing heavy "witness" marks as you like to call then. This thing really went thru some stuff.

Lastly, I need to know if the area in between the cush drive and M1 has any bearing on integrity and/or performance. If I run my fingernail over it, it's very gouged/ridge-like. Should it be replaced?

[HondaMan]

Those scratch marks on the mainshaft (the last picture) are pretty common, I see them often. There's nothing in the engine that can (normally) touch that area when it's all together. I'd suspect that handling of the part when it was moving thru the shop at Honda caused them.

Those clips in the first picture look to be in the right direction: do you recall if the rounded side of those (toothed) thrust washers were set toward their respective gears? This would put the flat side of the washers toward the rounded side of the clips, which would be correct.

Boy, those gear-dog marks against the inside of that gear's receiving dogs (picture 3) are nasty! That shows some serious sideways push, like maybe the clip was out-of-groove and let the gears get too friendly? Those thrust washers are there to corral them when they slide back & forth for shifting, with the clips to corral the thrust washers.

[scottly]

Boy, those gear-dog marks against the inside of that gear's receiving dogs (picture 3) are nasty!

Mark, I think those marks are from the endmill that cut the inside of the dogs, rather than the ends of the dogs rubbing against them?
I was mistaken about what I thought was the crack...

[Ellz10]

So an interesting thing I noticed today. The thrust washer that came assembled on the mainshaft is the stock one from the factory back then and it has the chamfered side, but the replacement thrust washer I bought new to replace the old one has a superceded part # 90451-MB2-000 and it is flat on BOTH sides, no chamfered side whatsoever. Because it's an updated part #, should I go with it and replace the old one, or would it be best to reuse the old one that has a chamfered side?

[scottly]

The flat washer is fine. It's the chamfer on the snap rings that's critical.

[HondaMan]

Yeah, what he said.... ^^^


You may also find that the new one is slightly skinnier. That's what I have noticed. I have little doubt that Honda only ordered them finished (flat ground) on one side to save Yen, that's the sort of thing they had to do to keep their prices where they wanted them back when. You'll find 'touches' like that all over these bikes.

[Ellz10]

Yeah, what he said.... ^^^


You may also find that the new one is slightly skinnier. That's what I have noticed. I have little doubt that Honda only ordered them finished (flat ground) on one side to save Yen, that's the sort of thing they had to do to keep their prices where they wanted them back when. You'll find 'touches' like that all over these bikes.

I'm curious to know about the 2nd circlip (the one I circled in the photo). I know you said I had them placed correctly (with the left one's chamfered side facing left (towards M1 and the Cush drive) and the right one's chamfered side facing right (towards M5)), but I remember reading that you said the chamfered side of these circlips should face the gear that is moving and could potentially come into contact with. Wouldn't the gear that has sideways play - gear M4 - ergo a moving gear, be the gear that is moving and potentially come into contact with that circlip?