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

[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?".

[calj737]

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.

There is no possiblity that the location of the crack in his pictures could EVER cause enough distortion to make the cases not close. I'm not sure what situation you had, but the repairs must have been significant (I'm thinking the dreaded case crack from a broken drive chain) to need to re-machine the mating surfaces. And a competent machinist would have welded above the mating surface then either milled or fly-cut the repaired area flush to the mating surface. Job done. 3 times? What the Ef?

There is so much internet mythology to the "welding distortion" with aluminum that unless you weld, you should refrain from advising people (not directed at you, Mark, anyone in general that opoines). Aluminum is a major heat sink. It takes an incredible amount of heat to staturate these cases that TIG welding up a crack will never produce sufficient damage.

My original counsel to jig it up was due to misunderstanding where the crack was from his picture. Where these pictures show, its no big deal. A 30 minute repair, both sides. It would take longer to pack and drop off at the shipper than to repair it.

[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?

[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.

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?

Normally, you'd be correct: as it happens in this gearbox, that gear only comes up to about 3-4mm away from that site when shifted against that ring/washer/gear. It can't make contact under normal circumstances unless the shifting fork was real bent, so you won't see any wear marks on that face of the gear - unless soemthing is broken. That actually happens sometimes with the C2 gear on the countershaft (bent fork) when the bikes fall over onto the shifter somehow, but I've not seen it happen with the mainshaft gears.

[Ellz10]

Just wanted to jump on here real quick and say I'm buttoning up the motor tonight and tomorrow, then throwing her back in.

I am curious about one thing I noticed. I see these "witness" marks, for lack of a better term, and I'm just curious if these are normal to see on the inner clutch plate housing?

[Ellz10]

Well the motor is back in the frame finally. Time to button everything back up and start her up again and get tuned in.

However, I went to pull the plugs from when it was running and what I found was that spark plugs from cylinders 1 & 4 are very black and dry, HOWEVER the spark plugs from cylinders 2 & 3 are very black but wet.

I'm more concerned with the plugs being wet more than anything else. What could the issue be and is it something I can fix?

[calj737]

I would discard those as offering ANY usable info given the issues with the bike prior.

They all show too rich a condition, but that could be from idling/lugging the engine cold with the choke applied. Get it fired up, synched, and go for a test ride top confirm your gearbox is correct. THEN turn your attention to tuning.

[Ellz10]

I would discard those as offering ANY usable info given the issues with the bike prior.

They all show too rich a condition, but that could be from idling/lugging the engine cold with the choke applied. Get it fired up, synched, and go for a test ride top confirm your gearbox is correct. THEN turn your attention to tuning.

That sounds like a plan, so I will do just that!

Thank you Cal.

[HondaMan]

Just wanted to jump on here real quick and say I'm buttoning up the motor tonight and tomorrow, then throwing her back in.

I am curious about one thing I noticed. I see these "witness" marks, for lack of a better term, and I'm just curious if these are normal to see on the inner clutch plate housing?

Yep, completely normal - and those are quite 'young' compared to most.

[grcamna2]

Just wanted to jump on here real quick and say I'm buttoning up the motor tonight and tomorrow, then throwing her back in.

I am curious about one thing I noticed. I see these "witness" marks, for lack of a better term, and I'm just curious if these are normal to see on the inner clutch plate housing?

Those are in very good shape 

[denward17]

Ellz, are you riding yet?

Waiting on updates....................

[Ellz10]

Ellz, are you riding yet?

Waiting on updates....................

Working on it. I had to hit the pause button due to FINALLY buying a house after 3+ years of searching. I ended up getting a good deal, but the lady was a massive hoarder and had 6 cats so the whole place reeks. The yard (Front and back) hasn't been raked, mowed, or even stepped on since 2016 - according to her neighbors that never saw her in the yard - and it definitely shows.

So I've been quite busy having my brother felling trees in the front back and side yards, hauling all the brush, splitting wood, pulling bushes roots and all with the tractor, replacing the roof of the shed that had 3 trees fall on it over the years and just left, tilling the entire yard, then seeding.

And I haven't even started on the inside yet. I gave the lady an extra 30 days after close to be out and clean out all her stuff.

So it's been a very hectic month.


All I have left to do is install the oil pump (The SumpThing), throw the carb on, and install the exhaust. Then I just need to adjust the air-fuel ratio and that should be fun.

I'll update here when I'm at the starting up stage (again).

[denward17]

^Good Luck with the house, that definitely takes precedence.

[newday777]

Congrats on getting your house.

[scottly]

All I have left to do is install the oil pump (The SumpThing),

Did you take the oil pump apart and clean all of the glitter out of it?

[grcamna2]

Ellz, are you riding yet?

Waiting on updates....................

Working on it. I had to hit the pause button due to FINALLY buying a house after 3+ years of searching. I ended up getting a good deal, but the lady was a massive hoarder and had 6 cats so the whole place reeks. The yard (Front and back) hasn't been raked, mowed, or even stepped on since 2016 - according to her neighbors that never saw her in the yard - and it definitely shows.

So I've been quite busy having my brother felling trees in the front back and side yards, hauling all the brush, splitting wood, pulling bushes roots and all with the tractor, replacing the roof of the shed that had 3 trees fall on it over the years and just left, tilling the entire yard, then seeding.

And I haven't even started on the inside yet. I gave the lady an extra 30 days after close to be out and clean out all her stuff.

So it's been a very hectic month.


All I have left to do is install the oil pump (The SumpThing), throw the carb on, and install the exhaust. Then I just need to adjust the air-fuel ratio and that should be fun.

I'll update here when I'm at the starting up stage (again).

Buying your property/house 

[Ellz10]

^Good Luck with the house, that definitely takes precedence.

I'm going to need it! I've exercising muscles I didn't even know I had! In fact, I've been moving and doing so much that yesterday on the drive back to our condo, I was on the Harley and I had to pull over immediately due to a charlie horse in my quadricep on my right leg!

Congrats on getting your house.

Thank you!! It's been such a long time coming. We put in 12 offers over the last 3+ years, just to be outbid each and everytime, almost always by all-cash offers.

We're pretty excited and the neat thing about a rough house/fixer upper is that we get to mold it to what we want it to look like.

All I have left to do is install the oil pump (The SumpThing),

Did you take the oil pump apart and clean all of the glitter out of it?

I did, yes! After you (I think it was you?) had suggested to do so because of any metal flakes that could've gotten in there, I figured it was the best thing to do.

[Ellz10]

Ellz, are you riding yet?

Waiting on updates....................

Working on it. I had to hit the pause button due to FINALLY buying a house after 3+ years of searching. I ended up getting a good deal, but the lady was a massive hoarder and had 6 cats so the whole place reeks. The yard (Front and back) hasn't been raked, mowed, or even stepped on since 2016 - according to her neighbors that never saw her in the yard - and it definitely shows.

So I've been quite busy having my brother felling trees in the front back and side yards, hauling all the brush, splitting wood, pulling bushes roots and all with the tractor, replacing the roof of the shed that had 3 trees fall on it over the years and just left, tilling the entire yard, then seeding.

And I haven't even started on the inside yet. I gave the lady an extra 30 days after close to be out and clean out all her stuff.

So it's been a very hectic month.


All I have left to do is install the oil pump (The SumpThing), throw the carb on, and install the exhaust. Then I just need to adjust the air-fuel ratio and that should be fun.

I'll update here when I'm at the starting up stage (again).

Buying your property/house 

No! 

We've got so much work still ahead of us, it's crazy! We're doing new hardwood flooring, new paint and then updating railings (it's a bi-level with a few steps up and a few steps down when you first walk in), and then we'll be moving in and continuing with rennovations as we go!

[grcamna2]

Ellz, are you riding yet?

Waiting on updates....................

Working on it. I had to hit the pause button due to FINALLY buying a house after 3+ years of searching. I ended up getting a good deal, but the lady was a massive hoarder and had 6 cats so the whole place reeks. The yard (Front and back) hasn't been raked, mowed, or even stepped on since 2016 - according to her neighbors that never saw her in the yard - and it definitely shows.

So I've been quite busy having my brother felling trees in the front back and side yards, hauling all the brush, splitting wood, pulling bushes roots and all with the tractor, replacing the roof of the shed that had 3 trees fall on it over the years and just left, tilling the entire yard, then seeding.

And I haven't even started on the inside yet. I gave the lady an extra 30 days after close to be out and clean out all her stuff.

So it's been a very hectic month.


All I have left to do is install the oil pump (The SumpThing), throw the carb on, and install the exhaust. Then I just need to adjust the air-fuel ratio and that should be fun.

I'll update here when I'm at the starting up stage (again).

Buying your property/house 

No! 

We've got so much work still ahead of us, it's crazy! We're doing new hardwood flooring, new paint and then updating railings (it's a bi-level with a few steps up and a few steps down when you first walk in), and then we'll be moving in and continuing with rennovations as we go!

A lot of work,but worth it once it's complete.