I Sign my Work with Excellence

Posted: Aug 17, 2007 09:29 PM  (Msg. 1 of 13)

Well guys,........I got pissed.        

Yup,....seems Black Thunder'd be shifting rather hard when really warmed up.   First Gear was really tough to find, and sometimes the KA-CHUNK when shifting just made me wince,....which grated my nerves.            ENOUGH!

So I took the Shifting Mechaniasm Cover off (after drainging the Oil first) and reconnected it all up so I could watch what's going on in there.    

Things looked okay,....I guess.   But there's something wrong here.    So,...I watched it shift up and down many times,..and felt a Grinding Feeling in the Shift Lever.  Traced it back to the Gearshift Cam Driven Gear. (the Middle Piece with the Teeth on it in this pic)



Seems that even though it is bolted in tight by the Gearshft Cam Retainer, it still has some "Float" to it.      This isn't the problem, it's the wear it causes on the inside of Driven Gear Retaining Plate (that Curved Flat Plate on the Right).  

Take a look at the Inside View:



There's alotta Scratches in that Shiney Spot you see.    How'd they get there?  

Well......Seems the Gear Shifting Lever makes the Driven Gear shift "Sideways" a tad on it's shaft (remember that "Float" I mentioned?)   and this Sideways Thrust causes the Driven Gear to move outwards and smack into that little "Tab" on the Retaining Plate, grinding into it and causing Hard Shifts.  

Why this happens is that the Gearshift Lever is Stamped,.....what that means is the the Teeth on it aren't totally square and have a rounded edge to them on the inside, and very Sharp-edges outside (as it's mounted).     You can see the Sharp Edges in this Pic:




So,.......what's the Fix there, Ed?                            Glad you asked!!

What I did was to first File Down the Sharp Edges of the Gearshift Lever Gearteeth.   Then I took careful Filework to that Tab on the Retainer Plate, and then Sanded it down to 320 Grit (almost a Polished Finish).      Here's a Drawing to follow:





Why I did this is that, being so small, there must be alotta Pressure on the Little Tab I figured.    And what with the Driven Gear "Floating", it must not always Lay Flat on that Tab, and rub mostly on the Shraper Edges of it.  

The results?     

Man,...does it Shift Smoother now.        I still can't Downshift from 5th to 1st at a Full Stop, so I must Downshift as I Roll to a Stop (that must be an Internal Parts Issue).      

But the loud KA-Chunk,..is reduced at least 40% (Sometime even more).     And Upper Gear Shifts are a Beautiful Thing.
Edited by Designer on Aug 18, 2007 at 07:32 AM

"I'LL SHOOT ANYTHING FOR MONEY"

Posted: Aug 17, 2007 10:22 PM  (Msg. 3 of 13)

Why not just replace the worn part?

Voted for the Hero

Posted: Aug 18, 2007 04:47 AM  (Msg. 5 of 13)

Designer,

Why not add a spring washer or bronse shim to zero out any play?  (The Float you refer to in the above, as usual, extremely informative post.)

"I'LL SHOOT ANYTHING FOR MONEY"

Posted: Aug 18, 2007 07:40 AM  (Msg. 7 of 13)

Quote:

Won't all the round edges allow it to pop out of gear?

Posted: Aug 18, 2007 10:11 AM  (Msg. 9 of 13)

This goes a long way to explaining why the shifting on my old Virago went from sorta clunky to nearly glass smooth over the span of 40K miles.  My Intruder, bought at 4K miles, now has 28K miles on it.  It's shifting was clunky, is still sorta clunky, but is slowly getting smoother all the time.

To bad the manufacturer doesn't take a few extra seconds on those stamped parts to deburr and/or smooth them before installation.

Regards, Gary in Sandy Eggo

Posted: Aug 18, 2007 01:24 PM  (Msg. 11 of 13)

Quote:

Great stuff!! And good observations. Could it be that they intended to put in a thrust washer at that point, but never did?  

But,, I'll wager that you will never get any MC tranny to downshift from 5th to first at a full stop!  I say this from my experience rebuilding my Honda 350. That one had a horizontally split case. I could lay the gears in one half of the case and turn them by hand and learn how they operated, and see precisely how shifts occur.  This was important, because I had a blown out counter gear, and a bad shifter drum. Had to replace all that.
I believe the sequence of events was, gear exploded, jammed up drum internally, and in my exuberance, I hit the shifter hard enough to break off the ratchet end on the drum.


Anyway, on the rebuild, I was able to study the tranny operation.  It never was able to go from 5th to 1st without some rotational movement. They all need some rotation to shift properly.  But,, As they go there is also a need for some slack,, which is why some of the gears transmit their power sideways through the "gear dogs". The gear dogs serve two purposes.

1. Allows a more compact design, In effect, "folding over" the gear train on itself. And, 2. The dogs have a "slide area" that allows a few degrees of rotation to allow engagement.  All the gears are always engaged tooth-to-tooth, but they are "active" or not based upon where they are slid on the gear shaft by the shifter forks.

How can they all be engaged all the time you ask? Some of them are indeed geared on the inside and turn at the same rate as the shaft they are on, while the adjacent ones rotate freely on the same shaft.

They engage through the dogs. The dogs and their slots allow for that movement.  The slots can be literally the oval holes in the side of the gear, that adjacent gear's round ones engage,, or they can also set-up as square pegs that stick out and engage flat-spots on the adjacent gear. But the characteristic common to them all is that they allow a few degrees movement.  Not just there for "lightening".

But for that movement to work and be fully effective,, there must be some small rotation in the system going on. Otherwise, you can indeed "shift" and make the gears slide, but many times the dogs don't fully engage, and will not allow further shifting.  They must go fully in and fully out. That is because in the rotation of the drum, the forks must travel in the tracks, meaning the track has to be fully followed and not short-cutted.

The entire poetry of the operation of the shifter drum and how such a simple and beautiful thing and be so complex and precise is something I'll leave to another day.  If you ever have the opportunity to handle a shifter drum and watch how the set of forks operates, it's relatively easy to see.  Three forks, each travelling in their own track, sliding back and forth and engageing/disengageing as they go.  It's a beautiful thing to watch!!  All out of three "squiggely" grooves!


Trogg

Posting now before I time out.........
Edited by Trogg on Aug 18, 2007 at 02:31 PM

Posted: Aug 18, 2007 07:41 PM  (Msg. 13 of 13)

Indeed! Also explains the shortness of travel, since even if the gears are slid over almost all the way, if the dogs are not engaged in the holes, then it's not in gear. The difference of being in or not is only about the thickness of the holes. (approx. 1/4 of the width of the gear.)  So popping out is a matter of moving only an eighth of an inch or so.

The full shift motion, as I recall is closer to a half inch.   Very neat thing to see!!

Trogg