Topic: Transmission gears + year compatibility? Rate my dogs and forks

[SKTP]

So I have a 1978 CB 750K — I have been working on it for awhile now. It is time to finally reassemble.

Somewhere along the line I acquired a transmission that I am unsure of the year of. The Shift forks look different but the gears look the same (and the dogs look MUCH better on Mystery year transmission)

So I am counting teeth and checking parts microfiche...It seems like they are interchangeable?

I am fairly sure I have read that the gearing changed somewhere along the line...what years have the same tranny gears?

[SKTP]

So I found this thread:
http://forums.sohc4.net/index.php?topic=107984.0
and I found some differences in the gears and shifter-forks. I don't know what year the good condition transmission is (ebay)

Here's the difference in the top shaft. No grooves (the lower, not pictured shaft, really seems to be identical...I have swapped them in and out and everything seems to turn...but I'm thinking I'll just stick with the known (I hope eBay again) 78K)



So after seeing that I'm either going to methodically go through the parts-fishe and see what's interchangeable

or...do you think my dogs looks ok?

[SKTP]

Sorry I am Monday-bumping this to get dog-opinions...rebuild #2 has to work!!! I bought OEM gaskets for Pete's sake!

[RAFster122s]

Wear on the ends showing as round off. The threads on undercutting gears might be a good resource. They don't look too bad in first pic but 2nd looks worse.

[SKTP]

So they are suppose to be 90 degrees? Are there good pictures of NEW/GOOD gear dogs online?
Is the transmission going to cost me a fortune?
Surely they can't be unusable? On a scale of 1 (terrible) to 10 (Factory perfect), how worn are these?

The mystery year transmission is visually less worn...but there's still some rounding (hopefully I can figure out if they can be swapped in/are the same). I don't feel like playing the ebay lottery...the photos of transmissions there are horrible

I just looked at gear prices and it's be well over 300 to OEM replace all the Dog-ones...

[RAFster122s]

Don't think that they are bad enough to cause them to drop out of gear. Forks tend to wear badly and cause more issues.  Teeth look good. The wear on the gear teeth should be away from edge of teeth and a consistent stripe across the face. They aren't adjustable like in a car. Different design and apples and oranges comparison really.

David

[SKTP]

This tranny did work for 300 miles.

Originally the bike's tranny failed and was locked into 2nd.

I put the 1978K ebay-buy tranny in and it worked other than 5th (I flipped a gear the wrong way during my first try)

Now I am doing a much more thorough rebuild. But financially, I'm pretty much finished (I hope)...but at the same time, if I've gone this far....

I do not want to rebuild it ever again...I want to ride it

I am hoping I will get many miles out of those gears

[Head]

What's the condition of the sifting forks? 

[SKTP]

[RAFster122s]

How does a transmission get locked into 2nd gear?
That implies shifting issues but your forks look very good with some wear on the farthest fork lower pad unless it is dirty.  They look good.

Ensuring that the stack is assembled properly on the shafts.

David

[SKTP]

The transmissions I am showing here are from eBay.

The one that bent a fork and ground into the gear and was stuck in 2nd has been removed and thrown away. This is the first motorcycle I bought and I learned to ride on it. I use to "engine brake" into first all the time when I was less educated and experienced...I suspect that's how damaged the original transmission. Here's a link to the Original damaged fork http://i297.photobucket.com/albums/mm202/ChristopherBywater/teardown%20008/download.jpg if you're interested...

I am getting ready to put this bike back together again (this time properly). The transmission shown in this thread worked and shifted well from 1-4 for 300 miles (with the exception of 5th, due to my flipping a gear upon assembly (or I really, really hope that's what happened).

I am willing to shell out the bucks for NOS tranny parts...but I really don't want to spend more money...but at the same time, I really don't want to have spent this much money only to have to tear it apart again

[PeWe]

...... "engine brake"..?
You downshift gear without using the clutch? Just slam it with excessive force like a brake pedal? Yes, that will bend forks....

Using engine break is the way I have controlled my bike all the time. 
With clutch ofcourse except when clutch wire was broken. It works when getting the feeling for it toghether with throttle to find correct moment  when gearbox is during less load.
+80.000km by me (100.000km's in total) and gearbox is still like it was from the very beginning. 17.000kms when I bought it.

CB750 std brakes are not much over 100kmh, using gearbox is a must. Only one disc brake front and rear drum brake is a joke. Rear will not apply much deceleration, more like wheel runs freely or completely locked sliding on the road.

[SKTP]

Well...I think I have decided to use the transmission...but I have purchased NOS OEM shifter forks in hopes of never having to split the cases ever again

I will post shifter fork comparison pics once the parts arrive.

[flybox1]

Seeing that I had to go into my trans 3 times, I would not uses those gears.
Next time i rebuild a 750, and i see worn dogs like that, they are immediately going to cyclex in exhange for some undercut ones.
EFF digging into an engine more than once I say!

[SKTP]

FAAAAAAAAAAAKKKKKKKK.....

OK...better safe than sorry I guess...more money and time it is!