Finding Neutral while stopped and in gear

TwoManyXS1Bs

TwoManyXS1Bs

BBQ Hunter
Top Contributor
Messages
14,670
Reaction score
15,294
Points
813
Location
Fredericksburg, Texas
This is a continuation of the Experimental Clutch thread:

http://www.xs650.com/threads/yamaha-xs650-experimental-clutch.47498/

In that thread, I've determined that the clutch isn't the primary cause of difficulty in trying to find Neutral while stopped and the transmission is in 1st or 2nd gear. In this this thread, I'll be experimenting with the shifting components, starting with the more easily accessed starwheel parts.
XS650 Shifter.jpg


This video shows typical XS650 shifter actuation:

 
During the shift from 1st to Neutral, or from 2nd to Neutral, one of the outer 2 shiftforks tries to slide a gear, and its dogs, out of engagement with one of the outermost wheel-gears.
XS650 Trans FindNeutral01.jpg


XS650 Trans FindNeutral02.jpg
 
Last edited:
When the shiftdrum rotates, one of its spiral cam slots will drive a pin inside a shiftfork, and shuttle a fork either left or right, causing the fork fingers to either shove a gear's dogs into an adjacent gear's slots, or pull that gear's dogs out of engagement with the adjacent gear's slots.

During this lateral movement, the shiftdrum acts like a screw, and its lateral movement must be confined by a 'shiftdrum stopper', which is a "C" shaped plate that rides in a narrow slot in the shiftdrum. This composite pic shows both sides of my original XS1B's shiftdrum stopper, a plate that also provides a hook point for the indexing stopper wheel's spring.
ShiftDrumStopper.jpg
 
Last edited:
These closeups show the very narrow zone of contact of the stopper and the shiftdrum's slot.

This is the top, visible, outside surface of the stopper plate. This is the bearing surface during a shift from 2nd to neutral, since the shiftdrum is being pulled into the case while trying to pull a slider gear out of 2nd gear. Notice the deep wear marks.
XS1B-ShiftdrumStopperTop.jpg


This is the bottom, nonvisible, backside surface of the stopper plate. This is the bearing surface during a shift from 1st to neutral, since the shiftdrum is being pushed out of the case while trying to push a slider gear out of 1st gear. Notice the even deeper wear marks.
XS1B-ShiftdrumStopperBot.jpg
 
Since the shiftdrum is rotating during these push/pull actions, any extra friction between the shiftdrum and stopper will hinder shifting. Possibly leading to binding. So, my first experiment was to polish those wear zones on the stopper plate, and see if shifting would improve. Sorry, no pics of the polishing.

The result was 'worse' shifting. Very interesting.

A new stopper plate arrived, and will be part of the next stage of these experiments...
NewStopperPlate.jpg
 
Last edited:
You're always up to something! I'll be watching this with interest. Always cool to how these problems are remedied or just ways to go about trying to help it. Hope you see some good results! Are these parts readily available, or would one need to source in good condition used parts?
 
TwoManyXS1Bs said:
Since the shiftdrum is rotating during these push/pull actions, any extra friction between the shiftdrum and stopper will hinder shifting. Possibly leading to binding. So, my first experiment was to polish those wear zones on the stopper plate, and see if shifting would improve. Sorry, no pics of the polishing.

The result was 'worse' shifting. Very interesting.

A new stopper plate arrived, and will be part of the next stage of these experiments...
View attachment 90159
Click to expand...
I am curious how temperature fits into this. In a previous thread you mentioned this as a common theme with finding neutral and or hard shifting. My XS650 is at the shop getting the big fin kit installed. I opted to stay with 650cc, all in a quest to reduce cylinder temperature. Has anybody installed the radiator type oil cooler? Did it help with finding neutral on these bikes?
 
JesseeS said:
You're always up to something! I'll be watching this with interest. Always cool to how these problems are remedied or just ways to go about trying to help it. Hope you see some good results!
Click to expand...

Hey, JesseeS. Glad you're enjoying this.
"How stuff works" always interests me too.

JesseeS said:
Are these parts readily available, or would one need to source in good condition used parts?
Click to expand...

I think it's kinda like fishing. Right place at the right time, use the right bait and gear, study the fishing holes, and hope that the pond isn't fished-out...
 
ihaxs650 said:
I am curious how temperature fits into this. In a previous thread you mentioned this as a common theme with finding neutral and or hard shifting...
Click to expand...

Been pondering this too. All I can think of is the oil viscosity, and the pressure drops. The shiftfork guidebar receives gallery oil pressure, but quite a way down the line, so it won't see much while hot. That oil pressure may help the shiftforks to glide/float on the guidebar, reducing the chance of binding...
 
Disassembled the shifter/starwheel stuff to do a preliminary inspection.

Found the indexer stopper wheel with a loose rivet pin, and a bit of wear on the pivot post and pivot hole.
IndexerStopper.jpg

Then examined the stopper plate and compared it to the new plate. There's some casting flash in the ID of my old plate, which shows some scraping. The NOS plate doesn't have this protruding edge.
OldNewStopperPlate.jpg

Examined the starwheel pins, and found fine scratch lines that align with the stopper plate's casting flash. Probably rubbing/scratching here, causing shiftdrum drag.
StarwheelPinScratch.jpg

The inner surface of the shiftdrum groove, in which the stopper plate rides, shows significant wear.
ShiftdrumGrooveWear.jpg
 
I wanted to know the force translations of the XS650 shifter, how much force is realized at the shiftdrum from force applied to the shift petal.
XS650-ShifterLeverages.jpg

What I get is 0.55 ft-lbs of torque on the shiftdrum for every 10lbs of force applied to the shift petal. But, that's when a starwheel pin is pointing straight down, which only happens at Neutral. When in a gear, two pins are +/- 36° either side of straight down, reducing the realized torque to 80%, or 0.44 ft-lbs of torque for every 10lbs of shift petal force.

This means that to get a paltry 1 ft-lb of torque on the shiftdrum, you'd have to apply at least 20 lbs to the shift petal. (*grunt*)
 
Last edited:
With the indexer stopper wheel removed, neutral detent plunger removed, neutral switch removed, and new stopper plate installed, I was able to easily rotate the shiftdrum thru all the gears. Felt very little resistance.

Now, retry the "shift outta 1st" test, using the same 4lbs of rear wheel preload as done in the 'Experimental Clutch' thread.
preloadtranstest02-jpg.89986



This time, I was able to "shift outta 1st" as easy as the 2lb preload in the original test, using about 10-15 lbs upward force on the shift petal.
 
More observations. Comparing my old '71 256-type indexer stopper with a newer '81 341-type indexer stopper.
XS650-IndexingStoppers.jpg


The newer stopper has a slightly larger rivet post for the wheel, both at the head and the post's axle, by about 0.010" (0.25mm). The newer 341 spring has 13 winds as compared to my old 256 spring, with 9 winds. The newer spring will have a softer spring rate, reducing the effort required to rotate the shiftdrum over the top of a pin, while still keeping about the same seating force in the valley between pins.

The spring offered on MikesXS is the later '341' version, with 13 winds.

https://www.mikesxs.net/yamaha-xs65...-stop-arm-oem-90506-10022-90508-32559-00.html
 
Last edited:
The newer shiftdrum's starwheel section also has a unique 'notched' pin, which is in the Neutral position. The notch is about 0.080" (2mm) deeper than the other pins. This would further reduce the effort to shift into Neutral.
81XS650-Starwheel.jpg


Could this be the 'unknown' -01 revision to the shiftdrum's starwheel section in '77?

These subtle changes confirm to me that Yamaha was indeed trying to solve the 'finding Neutral' issue.

My challenge now is to see if I can do a similar mod to my 256 shiftdrum's pin...
 
Last edited:
Rigged up a way to measure the torque required to shift outta 1st into neutral while the tranny is preloaded with the 4lb weight hanging from the rear wheel.
71StarWheelTrigger.jpg


Reminds me of measuring long and draggy trigger/sear breaks on Mauser actions. Stock '71 tranny, neutral detent and switch removed, light/tiny instrument spring on indexing stopper. I'm getting 12-15 inch-lbs to rotate the shiftdrum outta 1st, and can feel the beginning stages of binding.

I can feel dog undercuts in 2nd thru 5th, but not in 1st. I have a couple of late model trans now, and they also have undercut dogs on 2nd thru 5th, but not 1st.

Trivia item. Notice the lack of matching case numbers on the bearing boss.

Wondering if it would be possible to replace the shifter guide bar in-situ...
 

Similar threads

M
Not shifting while idling
Replies
16
Views
861
bosco659
bosco659
C
XS750 question, starter not engaging neutral
Replies
4
Views
618
Bruno_c
B
bosco659
Inconsistent shifting
2
Replies
21
Views
2K
bosco659
bosco659
sailorsam
can't find neutral
Replies
4
Views
779
Jan_P
J
J
Hard shift/no shift
Replies
6
Views
928
Jusblowit
J
Back
Top