Topic: "Gong"ing transmission. case split! (w/pictures!)

[Pecantree]

My brother came for Christmas, arrived that afternoon with my 750K6 I'd parked in his garage. Had left it in NC because the gear box was making bad noises.  Thanks bother! I don't care what mom say's about you!
Bought the bike in May in Cleveland, rode all summer no problems, was gonna ride it back to Austin in October. Made it to Charlotte, NC.
By the time I limped into Charlotte the gear box was making a clank or gong sound above 1st gear. Going slow enough there was time for whatever was hitting to reverberate a little bit before it hit again. At higher speeds it was just noise. It would get worse as the engine warmed up
I got the engine out Saturday and split the case yesterday.
The PO had the chain come off the sprockets at around 20,000, It chewed up the counter sprocket cover and broke 2 of the mounting holes on the case. It did not crack, hole or split the case. Engine has 38,000 miles

Found a broken flange on the clutch lifter plate


Here's the split case


There is a lot of sludge under the clutch basket. Is this normal?


The gears and dogs look very good. The  circlips are in place and facing the right way.
The only thing I've found inside that I know is wrong is the inside bearing for the counter shaft is sticking out about 1/8"
Spacer behind, sposed to be like this, Thanks MC
The counter shaft pulled out of the bearing with minimal resistance.


Anybody have any suggestions of what to look for? Why would the counter shaft bearing creep out?
Thanks
Steve

[Rgconner]

The sludge is looking like oil mayonnaise... probably from condensation if it sat for a while.

Clean it out, don't worry about it.

[MCRider]

That bearing is OK, I think. It stands proud of the case just that much, IIRC

[MCRider]

Any bits in the sump?

[Pecantree]

Ron, found the spacer behind that "proud" bearing. Dang, I thought it might be that easy!
When I changed the  oil in Charlotte there were a few sparkles but not many, a dozen maybe in the bottom of the oil pan.
It didn't seem out of bounds. In digging thru the case's I'm not seeing any scraping or banging marks.

Both my brother and a local bike mechanic listened to it in Charlotte,  I may be crazy, but we know it's in there.

I put a dial gauge on the primary chain sprocket on the main shaft and it has a .004 side to side wobble when spinning.
The main gear on the final drive shaft has a .017 side to side when I push/pull. Spinning it only varies about .002.
I'm not sure what to look at next.
Steve

[MCRider]

I gotta say, noisy transmission is not a common symptom. Usually, they jump out of gear, eiterh at the shift moment or shortly after engaged. That's caused by a bent shift fork, and an attendannt wearing of the shift dogs, chicken or egg.

Noises usually come from clutches, though still rare. That broken clutch lifter plate is a symptom of someone disassembling the clutch, then reassembling it in such a way that the pressure plate splines and the hub splines don't mesh. Then when you tighten it down that lifter plate breaks.

Though the break is usually on the other side of the bolt hole.

Has anyone ever been in the engine or the clutch, before you?
I'm suspicious...

[camelman]

Take the shafts out and see if any of the gears wiggle on the shafts. 

[Pecantree]

Ron, The stake washer on the clutch nut had previous wear marks so I'd say the clutch had been into before.
I think the case was virgin.

In Charlotte we had the bike on the centerstand with the drive chain off. Got the engine hot and ran thru the gears.
In neutral the engine is just an old noisy 750. Shifting up from 1st you start to get the clang clang noise.  I used a large screwdriver as a stethoscope and the noise was definitely coming from the gearbox. The local bike mechanic, Jimmy, who's about 60. He listened and he was kinda amazed because these bikes usually don't go bad there. He was too swamped to have a whack at it.

To Recap.
The drive chain had come off the sprockets and done minor damage to outside of case around 20,000.
Somethings wrong with the gearbox
Happens when its hot
Something is banging inside
It's not banging into the case. (no marks or aluminum filings)
     (Dog banging into gear?)
Happens with gearing and slower than engine rpm.
The primary gear on the mainshaft has a wobble
The gear on the final drive shaft has a wobble
    (could the broken chain have bent the main shaft or gear?
    (could it have bent the final drive gear?)

I'll measure the forks tomorrow and examine the gears to see what wear pattern they have.
Here's a short youtube of the primary drive gear spinning.
https://www.youtube.com/watch?v=XqM_Ymv45B8&context=C3dfc5eaADOEgsToPDskI5NeIJxMFi1J834ZVzRu49

Thanks
Steve

[754]

 My guess is a bad bearing, allwing shaft or gear center to move..should be easy to tell once you lift a shaft and cluster. if gear gets far out of mesh there is probably wear marks on the other gear, but it would be hard to see if a bit of oil is on the teeth. Its open now, check everything..

 Clutch plate, mine did that last year..not from instal..its from being 37 years old...

[Pecantree]

754:  I don't feel any wobble in the bearings, even with the shaft inserted into the bearing. I will replace all of them.

What I do notice is side to side slop with the sliding gears.
The brass bushings are somewhat worn.
I set up the transmission in the bottom half with all the shifting stuff bolted on.
Here's the video of that. At 1 min in you can hear the dogs clanging into the receiving gear.
https://www.youtube.com/watch?v=cc5Mi4uFEDs

So, I think a combination of slop in the gear bushings and maybe bent forks is allowing the dogs to hit when not engaged.
How do I measure the forks if I don't have a good one to reference to?
I've read Hondaman's book and he shows measuring against a good fork.

Thanks
Steve

[camelman]

Those brass bushings inside the gears have a tendency to wear.  I've seen it before on these CBs, and TTR400 showed me where the 350F and 400F typically wear.  I would imagine a wobbling gear would easily bang around and make some sound.  I had something screach itself to pieces on one of my 350F engines last year and it took out neutral and first gear selection.  I have a feeling it was a loose 1st gear bushing, but I haven't undone the engine yet to check.  Anyway, knowing those bushings are worn is reason enough to get them rebushed.  Take the shaft into your trusted machine shop and have them make up appropriate bushes.  I don't know the exact material to use, but I'm sure someone will chime in.  The end result should be easier gear changes, possibly with less "clunking", and it might get rid of the sounds you are hearing.

Camelman

[scottly]

That does sound like dogs are banging into their mating gears. I would suspect the forks or a problem with the shift drum?

[HondaMan]

Pull out that clutch hub and make sure the cupped washer that holds the outer basket onto the mainshaft has the cupped side TOWARD THE ENGINE. If it is installed backward, the clutch hub will chatter, which can cause wear on the splines where it sits on the mainshaft. The symptom is a ringing sound in the mainshaft.