Topic: Where's my 5th gear? SOLVED!!!

[brandEn]

Dead blow and tap it all the way around. That's how I have gotten mine apart anyway

[HondaMan]

Had to put this off for a bit as I had to put my 15 year old lab down saturday morning...but I found some time today.  Engine is out, and upside down.  Unable to see much through the pan after I removed the oil pump.  So, all of my case bolts are out, and I need to pry the halves apart. 
I used threebond, and they are good and tight.
What are the safe pry points?

If you are SURE all the bolts are gone, you can pry across the drive sprocket (or its shaft) and the bottom case. I use a long prybar, it only takes one tug to "pop" them free. If that doesn't do it, I forgot a bolt someplace. My favorite 2 to forget are: the one inside the starter's hole and the little one at the right rear top corner (opposite the final drive side).

[scottly]

Have you read this thread yet?
http://forums.sohc4.net/index.php?topic=86429.0

Yeah, poor Gammaflat: that K6 was assembled wrong at Honda! I've seen them mis-assembled, but not often popped out like his was, due to it.

Poor Gammaflat?? I'm the one that had the frigging bike fall on me!

[70CB750]

Had to put this off for a bit as I had to put my 15 year old lab down saturday morning...but I found some time today.  Engine is out, and upside down.  Unable to see much through the pan after I removed the oil pump.  So, all of my case bolts are out, and I need to pry the halves apart. 
I used threebond, and they are good and tight.
What are the safe pry points?

Sorry to hear about your dog. 

[flybox1]

Thanks 70..

Pictures of my forks, dogs, and a vid of the gears.







Vid

No 5th gear....: http://youtu.be/BNxPnX9kYBg

[Nic]

That's quite a bit of play in the 5th gear but it should still engage, I'd like to take a look at the forks where the little round tab goes into the drum and the drum itself to check wear and clearance there. If that all looks good I'd want to assemble the selectors and see how the whole thing works with the cases together. It's really hard just looking at pics. To have no 5th gear at all is weird.

[CB750F2]

Good Morning FlyBox. I have assembled my spare transmission into the bottom half of a spare crankcase I have and I can see that there is much less axial play in the 5th gear than what I see in your video. I suggest that you assemble the main shaft gear train to the bottom half as well and then you can operate the gear drum and see what is going on. You need to check wear in the drum channel, selector fork fingers, selector fork bore and selector fork shaft and the selector fork channel in 2nd and 3rd gear. You could reduce the axial play in the 5th gear by adding a another or thicker washer between the gear and the bearing.
Someone from this forum kindly sent me a copy of chapter 11 of the F3 manual - this is missing in the manual downloaded from this web site. I can email you a copy if you want. Pat

[CB750F2]

According to the F3 manual there should be a 0.080" washer between the circlip and 5th gear and 0.039" washer between 5th gear and the bearing. Pat

[flybox1]

Hey Pat.
It'd be Great for you to email me that chapter.
flybox11@gmail.com.
thanks!

I'll get some fork and drum pictures up in a moment.....

[flybox1]

CB750shift drum:
 http://youtu.be/PJnAWbFOgAg

Photobucket is down for maint, but fork engagement tabs at the drum all look good....

[CB750F2]

You should receive Chapter 11 any moment now. Pat

[Nic]

750Fs suggestion to assemble all the gears and shifting mechanism into the lower case is spot on. You'll see exactly what's going on there.

[flybox1]

According to the F3 manual there should be a 0.080" washer between the circlip and 5th gear and 0.039" washer between 5th gear and the bearing. Pat

With these fixed washer widths...how do they adjust for the manufacturing variances Hondaman listed above?  Do they not have the need for thicker or thinner shims?

Yeah...I'll get it all assembled and run it thru...

[CB750F2]

Thanks Nic. Flybox will have to take a measurement so that he can locate the main shaft assembly in the correct position because the bottom half of the crankcase does not have the locating grooves for the half locating rings. Pat

[CB750F2]

If the washers listed are not suitable then you may have to put thicker or thinner ones. However, if you are considering changing the eighty thou washer to something thinner be aware that 5th gear is pretty close to the LH side fork and if you put too thin a washer 5th gear may foul on the fork. Anyway that is down the track a bit - concentrate on what is causing the problem.  Pat

[flybox1]

Yeah..these look good

[HondaMan]

Honda's "adjustment" of the 5th gear seems to show up most on the '77-'78 bikes, in my experience. This 'adjustment' consists of changing the outer shim's thickness (0, .5, 1.0, 1.5, or 2.0mm) to make the 5th gear stay closer to the middle of the crankcase. (It seemed to have something to do with their machining of the cases near that gear?) Or, it may also have to do with the inner race of that ball bearing on that end: some I have seen had a thinner one than others, with correspondingly thicker spacer on the outside of the 5th gear. (I'm speaking of the one on the mainshaft, here). This moves the gear either toward the clutch, or away from it: shifting it toward the clutch causes deeper engagement with the gear next to it.

I can't see your YouTube videos, this computer's too old. But, if you're working on the 5th gear in the bottom half of the case: the 43-tooth gear there can be installed backward, too. Some of those have a spacer on the bearing side (not all), which is a PITA to install. Most just have a spacer on the circlip side only. However: this won't cause loss of 5th gear that I remember: it can just make the 43T gear scrape the case.

[flybox1]

Thanks Mark.
My 5th is installed correctly, as are the circlip and thrust washer.  I also have sufficient overlap into 5th.

How much lateral play of the 5th gear is allowable?

[flybox1]

I've got 3.87mm insertion depth of the 2/3 gear into 5th.
Shifting through the gears is somewhat effortless.   I have to spin the main shaft at the primary drive sprocket, and as its spinning, 1st, N, 2nd, 3rd, are easy...shifting into 4th and 5th requires I lock the mainshaft in place by hand to keep it from sliding as I dont have the grooves for the bearing set rings.
One of the things I did notice is the engagement teeth of 2/3 would sometimes run into the ID engagement teeth of 5th...preventing them mating properly.
Is it centrifugal force that keeps the teeth in alignment here on the mainshaft to allow easy engagement?

At work now, but I can vid this later today.

Unfortunately I dont have a gear puller to get the mainshaft bearing off to measure the thrust washers and circlip around 5th.
Might have to find/borrow one.

[HondaMan]

I've got 3.87mm insertion depth of the 2/3 gear into 5th.
Shifting through the gears is somewhat effortless.   I have to spin the main shaft at the primary drive sprocket, and as its spinning, 1st, N, 2nd, 3rd, are easy...shifting into 4th and 5th requires I lock the mainshaft in place by hand to keep it from sliding as I dont have the grooves for the bearing set rings.
One of the things I did notice is the engagement teeth of 2/3 would sometimes run into the ID engagement teeth of 5th...preventing them mating properly.
Is it centrifugal force that keeps the teeth in alignment here on the mainshaft to allow easy engagement?

At work now, but I can vid this later today.

Unfortunately I dont have a gear puller to get the mainshaft bearing off to measure the thrust washers and circlip around 5th.
Might have to find/borrow one.

It's not a press-fit for the bearing: it probably just has some crud holding it in place. Maybe a little penetrating oil might help?
The 5th gear itself (on the mainshaft) should not move back & forth more than about 0.5mm.

I'm not 'seeing' the [mis-]engagement thing you're describing, in my head? I'll try to watch the video later. I can't see them at home, but can here at work. I have only 256k Internet at home.

[brandEn]

.5mm? Wow. That's not much. Mark you should look at my CB750 pops out of forth thread and see how much my fifth moves.

http://forums.sohc4.net/index.php?topic=134859.0

[flybox1]

I've got 3.87mm insertion depth of the 2/3 gear into 5th.
Shifting through the gears is somewhat effortless.   I have to spin the main shaft at the primary drive sprocket, and as its spinning, 1st, N, 2nd, 3rd, are easy...shifting into 4th and 5th requires I lock the mainshaft in place by hand to keep it from sliding as I dont have the grooves for the bearing set rings.
One of the things I did notice is the engagement teeth of 2/3 would sometimes run into the ID engagement teeth of 5th...preventing them mating properly.
Is it centrifugal force that keeps the teeth in alignment here on the mainshaft to allow easy engagement?

At work now, but I can vid this later today.

Unfortunately I dont have a gear puller to get the mainshaft bearing off to measure the thrust washers and circlip around 5th.
Might have to find/borrow one.

It's not a press-fit for the bearing: it probably just has some crud holding it in place. Maybe a little penetrating oil might help?
The 5th gear itself (on the mainshaft) should not move back & forth more than about 0.5mm.

I'm not 'seeing' the [mis-]engagement thing you're describing, in my head? I'll try to watch the video later. I can't see them at home, but can here at work. I have only 256k Internet at home.

Mark, picture it this way, when shifting from 4th to 5th...2/3 slides and mates into the ID of 5th....well, if the 2/3 gears are slightly offset or rotated, they bump into the ID teeth of 5th, preventing engagement.....and my question was, what (centrifugal force?) keeps these gears aligned  (when riding) so they engage when shifted? 
Like brandEn, I probably have 1-2 mm side to side play on my 5th

[CB750F2]

Ok. While you have 5th engaged push 2/3 gear towards the clutch end and push 5th gear towards the gear shift lever end and see if 2/3 gear clears 5th gear. You will have to hold the main shaft in its correct position while doing this. Doing this will take up any wear in the forks, drum etc. Did the missing photos arrive OK? Pat

[Nic]

My 5th gear has about 1/2 a mil play. The bearing should come off real easy. Stand the main shaft up on the clutch end and with 2 big screw drivers on both sides at once the bearing should lever up without much effort. Just lever in between the bearing and the gear 180° apart. If it won't move don't force it, use common sense as to how much leverage the 5th gear cog can take safely

[flybox1]

Ok. While you have 5th engaged push 2/3 gear towards the clutch end and push 5th gear towards the gear shift lever end and see if 2/3 gear clears 5th gear. You will have to hold the main shaft in its correct position while doing this. Doing this will take up any wear in the forks, drum etc. Did the missing photos arrive OK? Pat

Ok.  More info.
 .71mm slide side to side play in the 5th gear. I'll work on getting the bearing off after I put down these baby backs...
While in 5th, separating 2/3 and 5th, I still have teeth engagement, the shorter(every other) teeth of the 2/3 BARELY engaged....

See this wear picture.  Note the two wear patterns. One wider wear pattern looks normal.  The other shorter, more abruptly angled wear looks suspicious.
Thoughts?


Yes Pat, got the photos.  Thanks again!