[Axeman88]

It didn't appear to be an issue with the shifter segment retaining screw, which is tight.

I jacked under the swing arm, so I could freely rotate the rear wheel and back-drive the transmission to facilitate shifting through the gears. I didn't replace the clutch or anything on the right side, which is open, no oil in the engine. It shifts smoothly into 1rst, 2nd & 3rd, but hits what feels like solid blockage at ~2/3 of the required rotation to enter 4th.

At this point the transmission is in a false neutral. It's out of 3rd, but not in 4th. This suggests to me that Fork #12 is seized on it's slider rail. It could also be sliding gear #5 seized on the input shaft, but I'd expect just a little more play in the motion if that was the case.

I did a little experiment. I took a brass drift and hammered a bit on the shifter segment, trying to force it into 4th, while holding the shift lever hand out of engagement. It moved, barely perceptibly, and not far enough to enter 4th, still in neutral. But now, it didn't want to shift back down to 3rd, it was stuck in that false neutral. I had to hammer it back towards 3rd, then all was as before. This result seems consistent with my suspicion of Fork #12 seizing on its rail.

My theory is that my buddy was riding with ten year old degraded dirty oil in the bike, the engine was hot. He was riding in high gears, particles in the oil got between the shifter fork #12 and its rail. The group stopped, the engine cooled, Fork #12 cooled, contracted, and seized on its rail.

I'm still toying with the idea of filling the engine with penetrating oil, but it seems like it would take quite a bit of overfilling to submerge the suspected component. Splitting the cases will be a sure thing with a lot more labor.

I need to find out how the transmission is lubricated, and whether the removal of any component might give me access to introduce some targeted penetrating oil.

I have about one more day of work on my current project, a Honda Shadow 1100 ACE, then the V-Star can move to priority 1.

 

[Axeman88]

Hey Axe man,
I am faced with a similar sitcho. However, I tore my case down to put a used transmission in it. Well, I don’t remember where the little pins on the shift star go, if you have yours out and you know where those pins go in relation to the neutral detent on the star, I would appreciate it if you made a note and let me know I didn’t have fourth and fifth gear as well. Mine is an 00’ 650. Classic. Also, don’t rotate the camshaft when you have like a part lol.

Sorry, I can't be of too much help yet. I'm still working on pulling the engine out of the frame. Too many projects and too little time.

But, from Yamaha's parts drawing of the shifter segment, it looks like the long dowel pin is all the way at the counterclockwise position, and all three of the other pins are the same size.

Are those pins keying the shift cam drum to the shifter segment? If so, I would expect to find that only one position offers enough depth to fit the longer. #5 pin, and the other three positions would be too short to accept#5 and would only accept #4 pins.

Perhaps post pictures of the mating faces of the shifter segment and the shift cam drum, and everyone will benefit?

 

[Axeman88]

The XVS650 project was on the backburner. I spent about one day a month working on it, and now, months later, there's some progress. Incidentally, the XVS650 engine was very straightforward to disassemble. I had no problems or issues. The only "special" tool required was a more or less ubiquitous 120 degree puller, with some M8x1.25, 120 mm long bolts to pull off the rotor. I do have a full complement of standard sockets, etc though, as well as an electric impact driver, which was usefull, and I am good at improvising.

Everything is open, and I can see that the reason the bike wouldn't shift into 4th was because the 3rd pinion was seized on the splines on the input shaft. Here we are looking up into the trans. from the right lower side.

Here, all the guts are spread out, and the three sliding elements are in their neutral / disengaged positions.

A closeup image of the input shaft, and the fork associated with the 3rd pinion. It looks to me like the sliding 3rd pinion overheated, it's the only gear on the shaft with a black coating. The keyed 3rd pinion slides up in the image to engage the pinion for 4th, and down to engage the pinion for 5th. I can hammer it in both directions with a brass drift, but it takes a lot more force than it should.

Notice in this image comparing the fork for the 3rd pinion with the forks for the sliding gears on the output shaft, how much cleaner they are, no baked on carbon on the left and right sliders, only the center fork associated with the 3rd pinion. All the forks, including the blackened one, slide easily on their rails, which are nice and straight

So, it looks like the culprit is the 3rd Pinion, seized to the input shaft, but WHY did it overheat? I think the engine would have been operating in 4th or 5th when this occurred. How is the 3rd gear set, and specifically its sliding relationship lubricated?

Take-out sets of transmission guts can be found quite inexpensively, so that's probably how I'll proceed, but I'm also thinking about pulling off the 3rd pinion to investigate further. I guess I'll need a bearing splitter to pull the input shaft assembly apart? Any reason I shouldn't heat the 2nd pinion on the left end of the above image to make it easier to pull off?

Do people think there might be carbon buildup INSIDE the 3rd pinion, that I could file or stone off, and/or soften with solvent to restore correct sliding function?

 

[Axeman88]

For reference, I wanted to add this image looking into the right side case, with the engine split, that shows the positions of the transmission components relative to the crankshaft and the sump. I indicated the direction of rotation for each shaft and circled the input shaft and center fork where the problem lies.

 

[Axeman88]

More investigation shows me that the Shifter Drum and the button on the Center Fork that rides in the center track on the Drum look to be in very good condition. I don't see any dings, indentations, or wear in the track. There is minute marking of Button, which is suspect is from my own efforts to force the shift before I started taking things to bits. I was able to force the shift, by using a piece of plate keyed into the features on the face of the detent star, but it required more force than I would have been comfortable subjecting the shifter mechanism to. Here's a picture of the Shift drum looking at the center cam slot as it enters 4th and 5th.

I also put the tubular Rail on a piece of polished marble that I use as a poor man's surface plate (plate glass for even poorer men) and checked it for straightness. It is quite straight. I'd say no more than .0005" of daylight showing at certain positions as I rotate it on the plate. My thinnest feeler gauge is .002", and wouldn't fit. I'm calling the Rail good.

And I tapped the 3rd pinion into the position it wants to be for 1rst -3rd ratios, and assembled the Input Shaft assy, the Center Fork, and the Shifter Drum as shown below. The Input Shaft spun freely, and the Center Fork floated nicely in it's groove. The fork had a little lateral play (estimated .015-.020) back and forth perpendicular to the axis of the Input Shaft so it could float. Everything seemed pretty nice, no smoking guns.

Except, the Center Fork was definitely overheated, along with the 3rd Pinion. It appears straight, not bent or badly worn, but there is visible wear on the surface facing towards the 4th pinion. I believe this is where the heat came from to carbonize the oil on the 3rd Pinion and Center Fork. Here's the worn face:

I'm speculating that if a rider was inadvertently resting their boot against the shifter pedal, while in top gear, this might result in the Center Fork being pushed towards the 4th pinion side of the groove, which is the worn face side. If the fork was forced into contact for a while, not enough to shift, but enough to load the side face of the shifter, perhaps this could result in this wear and overheating?

Someone might be interested in the details of the gear shaft assemblies. Pictured below is the output shaft mostly disassembled, I haven't gotten the input shaft apart yet.

The free spinning gears have bronze bushings with little pockets, and the sliding gears are solid steel. The hollow shaft has a single drilled radial hole for each free spinning gear but none for the sliding gears. My guess would be the oil is supposed to ooze out the sides of the journal then travel outward to the perimeter of the free spinning gears, where it lubricates the mating sliding gear.