Author Topic: Where's my 5th gear? SOLVED!!! (Read 23046 times)

Nic · « **Reply #75 on:** July 03, 2014, 06:55:43 PM »

Regardless of what else you find, seeing as used trannys for these bikes are so cheap over there I'd be buying one to get a better 2/3 and 5th.

scottly · « **Reply #76 on:** July 03, 2014, 07:52:40 PM »

The problem seems to be related to the shifting fork not moving far enough to engage 5th gear, since it works when you do it by hand. Assemble the shift drum and forks and run it through the gears. My best guess is the "L" and "R" forks are reversed? Don't worry about those slight wear marks for now.

MRieck · « **Reply #77 on:** July 03, 2014, 08:22:59 PM »

Did you ever move the shift lever down a spline to give a more positive engagement into 5th? I have seen more missed gears from to the addition of rear sets/high set stock shift arms etc etc. There just isn't enough leverage to move them.
I'm sure a transmission scientist will get on here but it something I have seen and experienced many times the to high/to low lever. All this BS and I've never seen where your gearshift lever was/is.

scottly · « **Reply #78 on:** July 03, 2014, 08:27:46 PM »

If it was only the shift lever position, he likely would have had issues with all up-shifts??

CB750F2 · « **Reply #79 on:** July 03, 2014, 08:46:55 PM »

Scottly, I can see where you are coming from but if that was the case I don't think that you would get fourth either. The "C" fork would have no room to travel.
Robert, I have checked the lateral movement of 5th gear in my spare transmission and there is approx. 0.3mm movement. The long tooth of the 2/3 gear engages approx. 5mm and then 3mm when 2/3 gear is pushed back towards the clutch end. The shorter tooth engagement is about half those figures. Are those new bearings on the main shaft? If so have they had the grooves machined to suit the locating rings in the top crankcase? Just check that there is no excessive play there.
I am surprised that you didn't feel/hear the gears trying to engage. If you find nothing else I would increase the spacer behind 5th gear to reduce its lateral movement to 0.3mm - 0.5mm, replace the centre fork and fork shaft and also 2/3 gear and 5th gear if there are any doubts about their condition. I cannot think of anything else. Others more experienced in these transmissions may provide more positive answers. Pat

flybox1 · « **Reply #80 on:** July 03, 2014, 08:57:21 PM »

MReick...lever position was the first thing I changed after my first break in run. I went down 1 notch from my preferred position, and was still able to fully actuate the lever. Even changed my riding position a few times to see if I wasn't just shorting it. Nope. Still nothing.
Only once was I able to feel some teeth chatter at the top of the shift trying to engage 5th.

Shift forks correct, Scottly. L C R order on the shaft.

Pat, my long tooth engagement is about the same as yours. I'll work on getting this bearing off so I can measure the spacer. The bearing still does not want to budge

These are the original bearings and they have not been removed.
Appreciate all the help and ideas guys!
Rob

scottly · « **Reply #81 on:** July 03, 2014, 09:15:07 PM »

Quote from: scottly on July 03, 2014, 07:52:40 PM

The problem seems to be related to the shifting fork not moving far enough to engage 5th gear, since it works when you do it by hand. Assemble the shift drum and forks and run it through the gears.

Take a video; you already post one of moving the gears manually, and one of the drum rotating. We need to see one with the forks in the picture. And is the L supposed to be on the right side when the bottom of the case is upside down???

flybox1 · « **Reply #82 on:** July 03, 2014, 09:31:06 PM »

Quote from: scottly on July 03, 2014, 09:15:07 PM

And is the L supposed to be on the right side when the bottom of the case is upside down???

Only in the lower hemisphere

Don't confuse me Scottly...I've got them on as they should be

I'll shoot the vid in the morning....it's Miller time.

scottly · « **Reply #83 on:** July 03, 2014, 09:36:06 PM »

It confuses the crap out of me; that's why I asked.

Nic · « **Reply #84 on:** July 03, 2014, 09:45:04 PM »

Well I did suggest assembling the shifter and all things related there the other day, at least you'll see whats happening.

flybox1 · « **Reply #85 on:** July 03, 2014, 10:06:27 PM »

I've assembled it, gone thru the shifting, disassembled to try and remove the bearing, reassembled and disassembled again. I can do all the springs and levers around the birdcage without looking at the fiche

The mainshaft has to be supported or else everything shifts when going into fourth. Supported, I can get 2/3 and 5 to perfectly engage, and I also notice 2/3 sometimes 'runs into' 5th and the gear teeth do not engage because they are not aligned. I tried to describe this in a post above to HondaMan.
I will do my best to get this on video in the am.

scottly · « **Reply #86 on:** July 03, 2014, 10:13:07 PM »

The teeth sometimes not aligning is the same as when the dogs sometimes don't align unless the gears are turning. It's not the issue, IMO.

Nic · « **Reply #87 on:** July 03, 2014, 10:50:55 PM »

Quote from: scottly on July 03, 2014, 10:13:07 PM

The teeth sometimes not aligning is the same as when the dogs sometimes don't align unless the gears are turning. It's not the issue, IMO.

Yes mate, once everything is spinning in there that's not an issue. I'd try n clamp the mainshaft down, then turn it by hand while shifting, not a problem unless you don't have big enough clamp. I'm also wondering how big the screwdrivers are that you used to pry off the bearing. I've just put all new bearings in mine, they were all original, I didn't use a puller coz I aint't got one, the screw drivers worked on all of em. Oh well actually I did use a couple of tyre, that's "tyre" levers on the big one next to the primary hub.

CB750F2 · « **Reply #88 on:** July 04, 2014, 01:20:33 AM »

Robert, assemble everything as has been suggested including the shift lever and its linkage and go through the gear changes using the shift lever and see what happens. You may have done this already. Pat

Nic · « **Reply #89 on:** July 04, 2014, 01:26:56 AM »

I think he has but the main shaft moves when shifting to 5th, that's why I suggested clamping the main shaft down and then try it.

CB750F2 · « **Reply #90 on:** July 04, 2014, 03:07:44 AM »

Yep. Hopefully when Robert does that and operates the gears via the shift pedal he will see what is going on. If the drum is moving fully to the 5th gear position then those gears should engage. Pat

flybox1 · « **Reply #91 on:** July 04, 2014, 01:09:46 PM »

Ok. Here's shifting thru the gears, including the neutral.
Missed second engagement because it wasn't spinning fast enough
Rotation stops after I shift into fourth because I'm holding the mainshaft in place....

Shifting...: http://youtu.be/bQBxslHQaCU

Nic · « **Reply #92 on:** July 04, 2014, 03:34:39 PM »

Hard to say again, the only thing I did notice is that your 4th and 2/3 engage all the way in, my witness marks are about half that distance, it could be that the C fork is bent towards the left as you look in the video n therefore not pushing far enough to the right for 5th but it's all too quick to have a good look. It did look like 5th engaged to some degree though? I reckon get the bearing off and shim the 5th gear more to the inside n check the C fork is all I can say and replace the worn 2/3 gear n maybe the 5th, can't see inside to see what it looks like there.

flybox1 · « **Reply #93 on:** July 04, 2014, 04:30:17 PM »

Spacer under bearing @ .0215" Not even close to the .039"
So...if I can source a washer at or near this, it will reduce my 5th gear play down to .3mm (.012")

It's worth a shot. I'm out of ideas.... $:-\$

CB750F2 · « **Reply #94 on:** July 04, 2014, 04:54:15 PM »

Yes, 5th gear seems to be engaging. Do as Nic has suggested, change the spacer but also change the shift lever down a notch or two and repeat the test. Wait for others to chime in. I am going away for a few days and will not have computer access. Good luck. Pat

scottly · « **Reply #95 on:** July 04, 2014, 07:45:29 PM »

1+ that 5th gear on the main shaft is fully engaging. What about 5th gear on the counter-shaft?

CB750F2 · « **Reply #96 on:** July 06, 2014, 01:33:09 AM »

Scottly, the 5th gear on the counter shaft is splined to the counter shaft so for that to be a problem then the spline on the counter shaft or the spline on the gear would need to be damaged or teeth missing on the gear - easy to check though. Robert, I have just had another look in my spare setup and I suggest that you make sure that the drum is turning far enough so that the pin on the "c" fork is in the straight section of the groove in the drum and not still the section of the groove that is angled towards the shift level end of the crankcase. If it is not then with the sloppy engagement that you appear to have it may be possible that under load 2/3 gear is forced out of mesh. I would also suggest that you mark the 5th gear engagement position on the end of the drum outside the crankcases so that when you eventually reassemble you can check this position. Pat

flybox1 · « **Reply #97 on:** July 14, 2014, 02:38:37 PM »

Sourcing a proper thickness thrust washer, to go between the shifter side bearing and 5th gear on the mainshaft was impossible. I need your advice on the following...
-I received another thrust washer (.039"), installed it, and measured no difference in the play of my 5th, nor the engagement depth of 2/3 into 5th on the mainshaft when shifted from 4th to 5th.
So, I added it next to my existing one, reinstalled the bearing and checked for fit in both case halves. It fits with ease, especially with those small bearing set pieces in the upper case.
-Sliding side to side play in my mainshaft 5th gear has been reduced to .2mm (was over 1mm), and it spins without resistance.
-Shifting from 4th into 5th, the mainshaft overlap of the 2/3 gear inside 5th, is a just over 6mm(was ~4mm). From this point, when i try to separate the 2/3 and the 5th gear I still have 5mm overlap. The majority of the movement comes from 2/3 gear moving away.

In attempts to regain the use of my 5th gear, what would be the reason not to try this 'extra' shim in my transmission? I really see no inteference of any kind on the main or counter-shaft, but i'm not the expert here.....

Nic · « **Reply #98 on:** July 14, 2014, 02:48:04 PM »

Sounds good to me.

CB750F2 · « **Reply #99 on:** July 14, 2014, 07:10:53 PM »

Sounds fine to me as well. Pat

News:

Author Topic: Where's my 5th gear? SOLVED!!! (Read 23046 times)

Nic

Nic

Nic

Nic

Nic

Nic