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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: gohabsgo k75 on July 31, 2012, 11:32:26 AM

Title: Slips out of first
Post by: gohabsgo k75 on July 31, 2012, 11:32:26 AM
OK, this is a scary one.  I recently did a spline lube due to difficulty on the down shift.

The last few times out for a ride, I have had the bike slip out of first.  It seems like it only happens when I come to a stop and idle in neutral waiting for the traffic light to change.  Sometimes, I have to hit the shifter a time or two to get the 1st to engage but a couple of times after accelerating  to get to second, it has slipped out.  When this did happen, I
was immediately able to shift to second.     I first noticed this when I had the added load of a pillion rider.  Not sure what is causing this.  Anyone?

Regards,
Larry
Title: Re: Slips out of first
Post by: Rick G on July 31, 2012, 07:46:27 PM
If it does it repeatedly you have a problem inside the gearbox. The same thing was happening with my K75 and it turned out to be a bent selector fork which was not engaging the gear far enough with the other and letting it come back out when power was applied.
Solution was to replace the selector fork, 2 gears and the selector drum which is where the problem started by the hard anodising getting chiped away.
Title: Re: Slips out of first
Post by: gohabsgo k75 on July 31, 2012, 07:49:10 PM
That sounds expensive.  So far it has only happened a few times but I'll be keeping a watch out for it.  I was hoping it would be something simpler, like adjusting the clutch cable.

Larry
Title: Re: Slips out of first
Post by: Chaos on July 31, 2012, 07:58:13 PM
The early K75 transmissions had an aluminum shift drum that wore out and could cause bent forks (so my mechanic explained to me) Later, (post 88) had a harder drum and are superior.  If it gets worse (it will) it would be cheaper to just swap out the tranny with another K75, K100 or K1100 unit.  They go for a couple hundred in good shape. 
Title: Re: Slips out of first
Post by: pallum on July 31, 2012, 08:00:36 PM
It's happened to me a few times just because of bad technique. Really get that shift lever to the top of its travel when jumping to 2nd and hope that you've just been lazy lately.  :2thumbup:
Title: Re: Slips out of first
Post by: frankenduck on July 31, 2012, 08:10:59 PM
Quote from: pallum on July 31, 2012, 08:00:36 PM
It's happened to me a few times just because of bad technique. Really get that shift lever to the top of its travel when jumping to 2nd and hope that you've just been lazy lately.  :2thumbup:

+1
Title: Re: Slips out of first
Post by: Rick G on July 31, 2012, 08:29:32 PM
One other thing I have seen do it is the splined spacer behind the driven gear cracked in half and fell into the bottom of the box slowly followed by the dogs on the drive gear as it disentergrated bit by bit. It was a real big mess by the time he got home.
Title: Re: Slips out of first
Post by: pallum on July 31, 2012, 08:47:22 PM
Rick, you're supposed to be helping people, not scaring them  :nono
Title: Re: Slips out of first
Post by: gohabsgo k75 on July 31, 2012, 08:59:48 PM
This is an 87 with only 33,000Km on it.  I am hoping it is a) bad technique or b) clutch adjustment.  If it is not, then I'm sure it will start happening more and more.  Let's hope for the best.

Regards,
Larry
Title: Re: Slips out of first
Post by: frankenduck on July 31, 2012, 09:15:18 PM
Just shift assertively but don't jump on it.
Title: Re: Slips out of first
Post by: DRxBMW on August 01, 2012, 07:41:11 AM
Quote from: Rick G on July 31, 2012, 08:29:32 PM
One other thing I have seen do it is the splined spacer behind the driven gear cracked in half and fell into the bottom of the box slowly followed by the dogs on the drive gear as it disentergrated bit by bit. It was a real big mess by the time he got home.

How did the motObricK gal revamping a tranny on her K 1100 ever make out ?

Buttoned up yet ? Curious ?
Title: Re: Slips out of first
Post by: Rick G on August 01, 2012, 09:05:33 AM
Last I saw was a post about painting it and having problems with the fuel outlet being broken but zero on the gearbox.
Title: Re: Slips out of first
Post by: gohabsgo k75 on August 02, 2012, 04:45:53 PM
An update:  I adjusted my clutch per the guides.  Test run, I tried stopping several times in neutral and it is not slipping out of first any more.  Pretty sure it was bad technique or adjustment related.  However,  I seem to be back to occasional difficulty in the downshift if I don't go all the way up to fifth.  Say for example, I make it up to fourth, then need to slow down to stop, I can get stuck in fourth unless I press down pretty hard with my foot.  Kind of worried that something may be bent.  Any way to test these things out with out taking off the whole transmission?  I just did a complete spline lube about 1000km ago.  This K75 only has 34000km on it.

Added info:  It is a 1987 K75 that had been sitting for two years.  I changed the engine oil, gear oil and final drive oil when I got it at 32000km and then the spline lube at about 33000km.  It now has just over 34000km.  Should I change the oils again since it was sitting so long with PO?

Regards,
Larry
Title: Re: Slips out of first
Post by: Chaos on August 02, 2012, 09:33:40 PM
It might be worthwhile to add a can of rinsoline to the engine oil then change it after 500-1000 miles.  This would help keep the sprag clutch on the starter working properly.  That can be a big problem it screws up.  Also, I started using synthetic gear lube last year and shifting got noticeably smoother. 
Title: Re: Slips out of first
Post by: Rick G on August 02, 2012, 11:31:20 PM
Did you lube the clutch spline or just the drive shaft splines?
Title: Re: Slips out of first
Post by: gohabsgo k75 on August 03, 2012, 07:16:42 AM
Quote from: Rick G on August 02, 2012, 11:31:20 PM
Did you lube the clutch spline or just the drive shaft splines?

I went as far as taking off the swing arm and the next piece, I think is the transmission housing?  and lubed the male spline that sticks out of there.  Are you telling me I needed to go deeper into the transmission?  I didn't see a write up on that.

Regards,
Larry
Title: Re: Slips out of first
Post by: Rick G on August 03, 2012, 07:25:21 AM
The clutch usually isnt included in a spline lube and doesn't need to be done as often but the grease will dry out and the clutch can get stiff which causes difficult shifting, mainly on the down shift.
I have never had to worry about it with any of mine because I am always pulling them apart for some reason.
Title: Re: Slips out of first
Post by: frankenduck on August 03, 2012, 07:37:28 AM
Quote from: gohabsgo k75 on August 03, 2012, 07:16:42 AM
Quote from: Rick G on August 02, 2012, 11:31:20 PM
Did you lube the clutch spline or just the drive shaft splines?

I went as far as taking off the swing arm and the next piece, I think is the transmission housing?  and lubed the male spline that sticks out of there.  Are you telling me I needed to go deeper into the transmission?  I didn't see a write up on that.

Regards,
Larry

Clutch splines:

(http://i82.photobucket.com/albums/j246/smithduck/k75f/k75f_036.jpg)


(http://i82.photobucket.com/albums/j246/smithduck/k75f/k75f_040.jpg)
Title: Re: Slips out of first
Post by: gohabsgo k75 on August 03, 2012, 09:54:16 AM
Thanks duck.  Now that I see the photo's...  I only went as far as the transmission input splines.  I guess I missed the next layer, the female ones at the clutch output. How bad is that?

Today, I was adjusting my technique a little.  Being a little less aggressive on the down shift.  IE  waiting until rpms dropped to below 4000 to drop into fourth and then below 3000 to third.  Seems to have been less sticky that way.  What are the usual RPMs to use when downshifting from gear to gear?  Maybe most of this is due to my technique?

Regards,
Larrry
Title: Re: Slips out of first
Post by: frankenduck on August 03, 2012, 10:05:05 AM
You want to lube ONLY the trans input splines.  They will lube the clutch plate splines when you put the transmission back on.  If you put lube on the clutch plate splines then it gets pushed through when you put the tranmission on and can spin off onto the front friction surface of the clutch plate which can make your clutch slip.

Due to the collar on the clutch plate, any excess that gets pushed back out on the trans input splines will just spin off onto the inside of the bellhousing.
Title: Re: Slips out of first
Post by: frankenduck on August 03, 2012, 10:09:39 AM
Quote from: gohabsgo k75 on August 03, 2012, 09:54:16 AM
What are the usual RPMs to use when downshifting from gear to gear? 

It varies. When I'm doing 60 and want to pass I shift down to third and romp on it.

In general, K bikes like high RPMs.  Try  to always keep it above 2500 RPM when riding.