1st gear problem

[TwoManyXS1Bs]

That 11° sounds OK.
It leaves about 25° for dog engagement, better than 1/2 the action.

0.008" (0.2mm) endplay sounds a bit loose. Haven't seen any spec for that. That's when I'd fall back to my ol' thresholds of 0.002" (0.05mm) ideal, 0.004" (0.1mm) service limit.

The outboard end of the shiftdrum *can* be removed without splitting the cases.

http://www.xs650.com/threads/bearing-id-help.54116/

Post #79.
http://www.xs650.com/threads/1981-xs650-sh-restoration.53833/page-4#post-581707

Check the condition of the inner edge of the "C" stopper plate, and the mating slot in the shiftdrum end. Recommend a new bolt in there...

 

[dps650rider]

So here is what I have done so far and estimates of the amount of slop I found:

* I bushed the stopper lever assembly pivot point eliminating a degree or so of slop here.

* I elongated the mounting holes for the C plate stopper pushing the plate towards the pins so it is running on unworn surfaces. This reduced the shift drum end play from 0.008" to 0.006" and likely what it was from the factory. I plan on using blue locktight on the threads and high strength within the elongated holes to guarantee it doesn't move.

* By far most of the slop was caused by the loose screw at the attachment point between the shift drum and the end of the shift drum that functions as a ratchet mechanism. In hind sight I wish I had counted the number of turns the screw had backed out but it was probably between 1 and 2. One turn of this screw moves the drum about 0.030" away from the direction of 1st gear engagement.

* The end of the drum or ratchet mechanism is attached to the drum inside a bearing and attached by the screw that was loose. It has a locator pin the keeps it in the correct position. If the screw was snugged there was a couple degrees of slop caused by the fitment of the pin. I degreased the holes and the pin and put a couple of drops of high strength locktight in the holes before assembly to stop movement. Between this and using blue locktight on the threads hopefully this won't come loose again.

The 1st gear fork moves about 0.2" between neutral and first in about 35 degrees of rotation for about 0.006" per degree (probably a little more than this when you consider the ramp shape). Given the above I guesstimate I was losing 0.04" or more of movement of the fork travel into 1st gear as it was when I took it apart.

Using my parts engine case and trans on the bench I measured about 0.1" of travel between when the dogs hit to the point of being fully engaged. So I could easily have been losing half of that with all the slop.

 

[TwoManyXS1Bs]

Great report and analysis, dps650rider.

That "C" shaped stopper was giving mine problems.
More on that in here:

http://www.xs650.com/threads/finding-neutral-while-stopped-and-in-gear.47568/

 

[dps650rider]

In mine the C stopper barely went in deep enough to control drum movement, with an even more narrow contact patch that the pics in the thread above.

Any idea why they went to the 2 piece shift drum? I can see no particular advantage to it and when the screw comes loose it's a problem. Matter of fact the screw was a bit loose in my parts engine too. I suspect that the slop in the fitting of the shift drum locator pin started all of this, if it can move at all eventually it will ratchet the screw loose.

Going to put it back together and try it. With what I found and corrected I think I have a decent chance of it being OK.

 

[TwoManyXS1Bs]

...Any idea why they went to the 2 piece shift drum?

The 70-71 XS1s had the 1-piece shiftdrum.
72 XS2 introduced the 2-piece, with the roller bearing.
The shift claw, neutral plunger, and spring-loaded stopper wheel exert considerable side loads on the shift drum. The roller bearing would reduce any friction of the shiftdrum in its case opening.

Aside from the 1st gear ratio change in '72, all the subsequent changes to the transmission would influence the shifting character. I've strong suspicions that Yamaha was trying to address shifting issues, including the "find neutral" issue. Even the separator o-rings of the 71-73 clutches point in this direction...

 

[dps650rider]

So the early models had no roller bearing? Certainly can see where that would be important.

BTW, I filled the elongated holes on the C stopper plate with JB weld and then redrilled them. I used blue locktight on the threads of the mounting bolts only. I also cleaned up the inside of the C stopper just to guarantee there was clearance for the pins.

Anyway I got it all back together, prayed over it (the Lord is a better mechanic than me) and took it for a ride and no problems. Was easy on 1st gear at first but eventually thrashed it a bit both accelerating and decelerating, operating under a steady load, etc. and all good. One thing was also apparent, I had been noticing that shifting was getting clunky especially from 1st to 2nd. Now it shifts with precision with every gear change. Like a lot of things when something degrades slowly over time you don't notice it at first then when you fix it the difference is amazing.

Anyway, that screw will always be in mind as something to check when the cover is off or if shifting gets clunky again. The same screw on my parts engine was also loose, not backed out a turn or more like my runner but maybe a quarter turn to tighten it. It would only be a matter of time before that one would have done the same thing. I wonder how many bikes on the road are like this.

 

[TwoManyXS1Bs]

Good save, dps650rider.
That "C" stopper plate is NLA. Even though it's a hard, forged part, many used ones I see on eBay have some degree of wear on the inner surfaces. I'd like to to see suitable replacements, or refurb methods, come available...

 

[dps650rider]

Seems like the best solution would be to replace the needle bearing with a ball bearing.
Wonder how hard that would be to do...

 

[TwoManyXS1Bs]

Yes, some sort of retention groove/ring around the ball bearing shell, let the ball bearing handle all the radial and axial loads. Projecting out enuff to capture. Probably deep groove type. The backside of the shiftdrum's outer part (where the original "C" plate rides) would have to be turned down. A new "C" plate retainer to fit in the ball bearing's groove.

A thinker...

 

[dps650rider]

It will give you something to do in your spare time.

Thanks for the tips on the first gear problem 2M!

 

[dps650rider]

Thought I would add a picture showing what I did to the C stopper.

Sorry, don't know why this web page decided to rotate the image.

 

[TwoManyXS1Bs]

Yup, that one sure had some wear marks...