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

[Ellz10]

Bummer......

That's for sure!



I am curious about one other thing if anyone has an opinion or input on it - when I had the bike running, I  noticed that I could not get the bike to rev past 6k rpm. That was the highest I could get it and that was REALLY pushing it, even though there was still plenty of throttle left. Is it because of the larger cam or something else bad?

[scottly]

Is the glitter steel or aluminum? Does it stick to a magnet?

[newday777]

Bummer......

That's for sure!



I am curious about one other thing if anyone has an opinion or input on it - when I had the bike running, I  noticed that I could not get the bike to rev past 6k rpm. That was the highest I could get it and that was REALLY pushing it, even though there was still plenty of throttle left. Is it because of the larger cam or something else bad?

How did you dial the bigger cam timing?

[MRieck]

 CycleX did most of the machining?

[Ellz10]

Is the glitter steel or aluminum? Does it stick to a magnet?

I'll have to check tonight and get back to you!

Bummer......

That's for sure!



I am curious about one other thing if anyone has an opinion or input on it - when I had the bike running, I  noticed that I could not get the bike to rev past 6k rpm. That was the highest I could get it and that was REALLY pushing it, even though there was still plenty of throttle left. Is it because of the larger cam or something else bad?

How did you dial the bigger cam timing?

I explicitly followed the instructions on Webs website. I'll attach a photo. I used a TDC stop tool, big degree wheel, laser pointer for accuracy.

CycleX did most of the machining?

They did all of my machining.

[newday777]

Are you running points or electronic ignition?

[Ellz10]

Are you running points or electronic ignition?

Stock points.

[scottly]

Are you running points or electronic ignition?

Stu, what would the ignition have to do with the metal shavings in the oil and filter?? The motor has something chewing away at it's insides.

[scottly]

I am curious about one other thing if anyone has an opinion or input on it - when I had the bike running, I  noticed that I could not get the bike to rev past 6k rpm. That was the highest I could get it and that was REALLY pushing it, even though there was still plenty of throttle left. Is it because of the larger cam or something else bad?

Maybe the engine is starting to seize??

[newday777]

Are you running points or electronic ignition?

Stu, what would the ignition have to do with the metal shavings in the oil and filter?? The motor has something chewing away at it's insides.

In reply #25 he was wondering why it wouldn't rev past 6,000 rpm

[Ellz10]

Well first things first - I took a peak inside the exhaust ports and although I'm not knowledgeable at all when it comes to what it SHOULD look like, something tells me that this isn't it. Am I wrong?

All 4 exhaust ports are black like this one, covered in soot/char whatever you wanna call it. And then on exhaust port for cylinder #4 there's this wet, sticky substance. No idea what it could be.

Thoughts?

[calj737]

Looks like oil-soaked carbon deposits. Oil leaking past the valve guides perhaps? Obviously the fuel mixture is way off…

[scottly]

Something is chewing away metal inside the engine and you're concerned about carbon in the exhaust ports?? Are the shavings steel or aluminum? Did you have oil pressure? I would first pull the cam cover and have a peek under it. Any sign of shavings up there? If all looks well there, flip the motor over and pull the pan and inspect the bottom end.

[scottly]

Tomorrow I'm pulling the motor and splitting the cases to see what the noise is from and the gear sticking.

What noise??

[Ellz10]

Something is chewing away metal inside the engine and you're concerned about carbon in the exhaust ports?? Are the shavings steel or aluminum? Did you have oil pressure? I would first pull the cam cover and have a peek under it. Any sign of shavings up there? If all looks well there, flip the motor over and pull the pan and inspect the bottom end.

I am very concerned about both, or rather anything that could be detrimental to the motor. So the shavings were about 50/50. The bigger chunks/slivers were steel and the smaller pieces were aluminum. I had around 75 psi oil pressure when I did a soft start with plugs out and then around 75 still showing on the gauge when I started the bike and while it was running. I was trying to save myself the cost of yet another gasket, but at this point might as well look. I'm about to do so right now. I already pulled the SumpThing and the pan and that's where I found most of the bigger shavings.

Tomorrow I'm pulling the motor and splitting the cases to see what the noise is from and the gear sticking.

What noise??

I posted a video up above, it's a very short video, showing me driving by and as I do you can hear this clunking noise. That noise gets louder the faster I go and quieter the slower I go. As mentioned above as well, I was unable to move the bike shortly after that video was taken. Nothing, absolutely nothing would work and so that's why I'm splitting the cases again.

Looks like oil-soaked carbon deposits. Oil leaking past the valve guides perhaps? Obviously the fuel mixture is way off…

Not sure what to do here. Perhaps replace the valve guides? I think I'm going to worry about the bottom end first, then circle back to this. Good to know though so I can order the parts and have them ready.

[Ellz10]

So the really good news, at least at this point, is that there aren't ANY metal shavings or anything amiss in the top end, so I'll gladly take that as a win. Well aside from the fact, or assumption rather, that I have a valve guide leak, but I can always fix that later.

I'll update here when I have the cases split.

If anyone has any further input, please feel free to share!

[calj737]

To be clear, “valve guides leaking” is a hypothesis. Most likely route for oil to hit the chambers aside from the rings. And the rings could very well be the culprit given a fresh build and no “seating time” on them.

Fuel mixture would be best to address first after you resolve the clunking noise and source of metal shavings. Aluminum is less concerning than steel in the pan.

[Ellz10]

To be clear, “valve guides leaking” is a hypothesis. Most likely route for oil to hit the chambers aside from the rings. And the rings could very well be the culprit given a fresh build and no “seating time” on them.

Fuel mixture would be best to address first after you resolve the clunking noise and source of metal shavings. Aluminum is less concerning than steel in the pan.

I'll fix fuel mixture first then, thanks Cal!

[Ellz10]

Well I found the problem. It's just what I thought it was. There are 3 notches sheared off from 1 gear and 2 more from the one next to it. The corresponding gears resting in the opposite side case are shaved and ruined as well. I made sure to retrieve all 5 notches from the motor.

I want to mention this because I feel like it has some bearing to the problem - so the countershaft bearing holder when I went to remove it, WOULD NOT come out. It wouldn't budge at all. It took over half an hour of carefully trying to pry from every angle, then several minutes of the torch and finally I was able to knock it out. When I did the bearing was still on the gear shaft and not inside the holder. I mention this because before I removed it, the gear drum wouldn't move at all, just as it wouldn't when the bike was stuck in gear, it was stuck to the same limited motion, BUT when I removed the holder the gear drum twisted like it should. Not sure if it's related to the main issue, but thought I'd mention it.

I know this question might open a can of worms, but I would really like to know if anyone has any insight as to what could've happened.

What should my next steps be, aside from finding replacement gears?

[calj737]

Ouch. Double ouch. I'll be spending a moment of silence this afternoon in empathy for you. Is that bridge within throwing distance still??? 

[Ellz10]

Ouch. Double ouch. I'll be spending a moment of silence this afternoon in empathy for you. Is that bridge within throwing distance still??? 

Thanks lol. The bridge is right behind the house, so yup!

At least it's only 4 gears I'll have to replace, I guess it could always be worse!

[Shtonecb500]

Ouch. Double ouch. I'll be spending a moment of silence this afternoon in empathy for you. Is that bridge within throwing distance still??? 

lmao.

[Ellz10]

Well I must be lucky today because I was just able to find not one, but two listings on eBay for complete transmissions for a '77 and a '78. One for $85 and the other for $175. So I bought them both just in case. I'll post pics of the gears when they arrive so everyone can see the condition and I can go from there and decide which ones seem the best.

[denward17]

Would love to hear from some of the more experienced members here what would have caused this.

Could it be a misplaced washer/spacer or something like that?

[Ellz10]

Would love to hear from from some of the more experienced members here what would have caused this.

Could it be a misplaced washer/spacer or something like that?

I would VERY MUCH like to know that as well, so I can know what to look for, ect.