Overdrive 5th gear - Dropping/Slipping Out to Neutral

[glennpm]

Hi,

I have a 1979 XS650F that has about 400 miles on it since the Cafe style rebuild. I started with a rough but low mileage bike that had about 7,000 miles on the odometer. I went completely through the motor and transmission. The transmission gear dogs and shift arms all looked good in my recollection. I swapped out the stock '79 main shaft 5th gear with one of MikesXS overdrive 5th gears. I didn't have any problem slipping the replacement 5th gear onto the shaft like others have been having in the other 5th gear thread.

I am having trouble dropping out of 5th to neutral. It occurs just cruising along and not under a load change of deceleration, acceleration or climbing a grade. All of the gear selections are positive going up or down. Neutral can be elusive. This is what I've done so far:

- Chain was adjusted a little tight. Slackening it off, now as far as I wish to go, lessened the drop outs.
- The shifter shaft is tight side to side. with no excessive slack
- I pulled the right side case. The selector springs are not broken and seem to have adequate tension.
- The star wheel adjustment was a little bit off so I centered it in all the gear selections per the manual. It was tough loosening up the adjuster lock nut with the clutch basket in place and discs pulled out. This adjustment made no improvement.

I'm very reluctant to split the cases and hope that there may be something else I've missed. I'm also thinking about going through the rear oil drain plug hole with my HF boroscope camera and see if when rotating the position of 5th when selected and the condition of the dogs on its mate, when not engaged. It seems like the hole would be in a fair place for this inspection.

Any other non-splitting checks I can do?

Thanks

 

[TwoManyXS1Bs]

Hey, Glenn. There's a fiddlyfart test, done with the right cover and clutch removed. Hard to explain, but you get the transmission into 5th, then simultaneously rotate the output shaft and manipulate the shiftdrum into/out-of 4th and 5th gears. While doing this, make note of 4 things:

How far the shiftdrum rotates relative to the stopper (indexing) wheel when:

- 4th is fully engaged
- 4th is blocked (dog hits gearside)
- 5th is blocked (dog hits gearside)
- 5th is fully engaged

The relative differences give an idea to non-centering and offsets (for bent shiftfork), and to depth of engagement (gear recesses and clearances).

Gads, I hope that makes sense.

If you can find his thread, Aaron Kelly had the same 5th pop-out issue. It sounded to me like it was caused by incorrect depth/clearance in the aftermarket 5th gear...

 

[glennpm]

Hi TooMany!

Yes, it makes sense but how do I correlate the differences that I may find that point to what I find to identify the " non-centering and offsets bent shiftfork, and to depth of engagement (gear recesses and clearances)"?

This would be much better than opening the case and finding nothing obviously wrong ;-)
If I can get in through the drain plug opening, I could check the depth of engagement that way too.

 

[TwoManyXS1Bs]

... it makes sense but how do I .........

Yeah, this kinda thing is best done with the cases open, where you can see what's going on.
In this situation, it's kinda like trying to explain how to start a nut on a bolt with your eyes closed.
I don't know how to explain it. Have to visualize the sliding of the fork and gear while manipulating it, and use your 'feeling around in the dark' skills to make judgement calls. Use the 'deft touch'...

 

[glennpm]

Hey this kind of sounds familiar, " ... the sliding of the fork and gear while manipulating it, and use your 'feeling around in the dark' skills to make judgement calls. Use the 'deft touch'..." Sometimes four hands are better ;-)

I found the thread you mentioned, didn't see it in my searches this morning. Lots of good stuff there and wishing I hadn't put the new 5th gear in but maybe I wasn't looking closely enough at the condition of the dogs. It did look okay and shifted fine before I buttoned it up but sure would have been more careful if I'd know this was going to happen. Back of my mind was this thing only had 7k miles on it!

http://www.xs650.com/forum/showthread.php?t=26894&highlight=5th+gear

 

[TwoManyXS1Bs]

Good. You found the thread. Unfortunately, couldn't get to a solid resolution to the actual source of the problem.

Working in a shop, parts a-plenty, shop manuals nearby, good transmissions to compare with, and experience with numerous tranny foibles certainly helps.

But how can you explain all that, without writing a book?

Reminds me of that 'Big Bang' episode, where Sheldon learns how to swim, on the internet.

Here's a pic that shows the 4th-5th slider and gears, that may help.

 

[TwoManyXS1Bs]

Another thing. If you've followed threads like this, fellow posts a problem, and several post up possibilities. Eventually, the fellow gets in there, and finds the problem(s), which more than half the time is something else. Just required gettin' in there and fiddlin' about, lookin' for all the suggested possibles.

As long as you know how all that stuff is supposed to work, you're halfway there...

 

[TwoManyXS1Bs]

Here's another pic. If you look closely at the 3rd gear slider, you'll note that it's close to the 4th gear cogs, with too much space to 5th gear. If, when in neutral, yours looks like this, suspect a bent shiftfork...

 

[glennpm]

Here are pictures I took a couple of years ago during my assembly. Wish I had more now. Maybe there is some damage shown amongst them?

 

[TwoManyXS1Bs]

Can't see much looking end-on at your shift forks.
Member Marlin72xs has an album with good pics of his bent/damaged middle shiftfork.
That's one of the things that you'll be looking for.

http://www.xs650.com/media/albums/2581/

Can you see the scrub/scrape on the short leg?

 

[TwoManyXS1Bs]

Here's a thread of interest:

http://www.xs650.com/forum/showthread.php?t=40233

And, this is where Marlin72xs slips in:

http://www.xs650.com/forum/showthread.php?p=410926#post410926

 

[glennpm]

Yeah, when I took the pictures it was more for general record for myself not an autopsy! I appreciate you links and input. the first link you provided earlier has some GREAT information in it. Maybe you should change your logon name to Dr. Knows or something ;-)

Best,
Glenn

 

[TwoManyXS1Bs]

Errrm, well, we DO offer discount catscans...

 

[glennpm]

Yeah, I have "in house" resources that help me with the scans!

 

[glennpm]

Hi TooMany,

I'm having trouble seeing the problem here. Can you clarify please? I flipped your picture from above.

" If you look closely at the 3rd gear slider, you'll note that it's close to the 4th gear cogs, with too much space to 5th gear. If, when in neutral, yours looks like this, suspect a bent shiftfork..."

 

[glennpm]

Is this correct?

 

[TwoManyXS1Bs]

Glenn, yes, you've identified the non-symetrical gaps that last picture.

I suppose that I slip into a form of street shopspeak that's not really covered in the manuals.
And, this shopspeak doesn't necessarily conform to other published documents.
It was mostly used in-house to the parts guys and other mechanics, as a disambigous convenience.

Each 'gear' (or gearset) is composed of a mating pair of gears, in constant mesh, often referred to as pinion and wheel. One gear spins freely on a shaft (wheel), the other is fixed to its shaft (pinion), either by being a part of the shaft (as in 1st pinion) or as a 'slider' that slides on splines. The 'slider' also has dogs that engage adjacent cogs or slots, to attach that adjacent freewheeling member to the shaft, so, it serves double-duty.

The confusion came in as to who or what was describing these gears. Some referred to all gears on the mainshaft as 'pinion' or 'driving', and all gears on the countershaft as 'wheel' or 'driven'. The XS650 parts manuals call all gears on the mainshaft as 'pinion' and all gears on the countershaft as 'wheel'. Sometimes the terms 'mainshaft' or 'countershaft' were used to identify which gear, but the occasional use of the brit term 'layshaft' would add to the confusion again. Others used 'dogs' and 'cogs', or just the tooth counts, or the part number, or the term 'slotted', or something else that used a lot of swearing and arm waving.

Using the term 'slider' was just a shop convenience to avoid confusion (and bickering).

In your last pic:
1st gear is composed of the pinion and wheel gears at the far right (clutch) side.
2nd gear is composed of the pinion and wheel gears at the far left (sprocket) side.
3rd gear is composed of the pinion and wheel gears in the middle.
4th gear is composed of the pinion and wheel gears between 1st and 3rd.
5th gear is composed of the pinion and wheel gears between 2nd and 3rd.



Looking at the 3rd gear (middle) pair of gears, the lower gear is the 'wheel' and the upper wheel is the splined/sliding 'pinion', which we would have just called 'slider'...

 

[glennpm]

Super explanation TooMany!

Once I get tired of keeping my left foot wedged under the shifter when in 5th, I'll be splitting the cases. Probably going to wait until Summer is over though so I can some enjoyment out of the bike. First it was fun with carburetion and this issue was lurking in the "basement".


Thanks!
Glenn

 

[TwoManyXS1Bs]

Thanx, Glenn.

(*gasp*) I guess this is slowly becoming a book.

Something else you can try is to hold about half clutch pressure while in 5th. This would shove the mainshaft to the right if the double-row bearing is going out, or if the clutch hubnut is loose. If 5th engagement changes during this 'clutch pressure', then suspect those other conditions as well...

 

[glennpm]

Hi TooMany!

I mentioned above that I was thinking about using my HF borescope aka digital inspection camera to see if I could check 5th gear engagement without splitting the cases. I studied the different access hole from my pictures, front sump/strainer, rear oil drain plug, or slot from behind clutch basket into tranny cavity. It turns out that the rear oil drain plug was real good to use. Access from the front sump offered little access to see the gears but good for looking at the cam chain.

I poured over the pictures I had taken during re-assembly and noted that the new overdrive 5th has no marking grooves on the external teeth surfaces. The 3rd gear pinion has a single groove adjacent to 5th. I looked for these as I was poking around with my camera.

I jacked the rear wheel off the ground and removed the spark plugs to make it easier to turn the motor over. I could wiggle the camera probe around, rotate the rear wheel with my left hand or foot and shift the gears pretty much while lying on the right side of the bike.

I found that 3rd gear is spaced evenly between 4th and 5th, there is good clearance between the cogs of 3rd and 4th, 3rd gear dogs are in excellent shape with no damage of rounding, etc, engagement into 5th is solid and sure with no excess gap between the sides of 5th and 3rd.

I took three short videos. The first named, "XS650 5th gear video" starts with 5th gear engaged then I shift and rotate down to neutral and back up to 5th engaged. the back and forth is to get the gears to move a bit.

The second video, "XS650 3rd gear dogs" does a full rotation so you can see that all the dogs on the left side of the the gear are in great condition. These "dogs" lock into the slots on the side of 5th gear during engagement. Slots are fine too.

The third video, "3rd Gear Cog Clearance" is taken between 3rd and 4th gears. It shows the great condition and adequate gaping between them. Engagement to 4th gear is when the cogs interlock between these two gears.

So it looks like everything is fine and no indication that the clevis arm for the 3rd gear pinion gear slider is bent. If it was what I've mentioned and film sure don't indicate this.

Now what should I be looking at for the slippping out of gear issue? Yesterday I read the long thread where someone had engagement and re-engagement due to clutch issues. When I did my assembly I sanded and filed off all the sharp edges on the clutch pack metal disks and stacked them so the belling was all in the same direction. I was careful with the washers and shims using the color coded cross section drawing that I got on this site which came from a German maintenance manual. I have a reasonable gap on my clutch handle which increases as the bike warms up. My slipping gears doesn't seem to be connected to this gap.

Thoughts?

Thanks,
Glenn