False neutrals

[Matt o]

Hi all,

I have an XS400 Special and I’m experiencing false neutrals on almost every ride, it finds them whilst I’m already in gear and suddenly drops into a neutral. Also often get an unwanted jump from 4th down to 3rd. It can be challenging at times to drop through the gears to 1st when approaching lights.

I have read many posts on here and other forums and have since adjusted to shift pawl. I’m looking for any opinions on whether the shift spring could be causing this? I have ordered one anyway.

I’m hoping to find someone that may have had a similar experience and that could give me some guidance.

How does a gear change feel on your bike? Mine is less than convincing and I barely know that I’ve made a change.

Thanks for any input in advance.

Matt

 

[amc49]

Yes. Look at spring and whatever holds the shifter linkage solidly in the place you last put it. The detent is not holding enough to both click solidly into place and solidly stay there once there. If it has been run long enough the looseness will then round off the sides of the dogs that are on the gear sides, rounded off the gear will then pop out of gear. Meaning gears then need changing too, why you have to fix detent issues quick to avoid deeper damage. It can lead to bent shifting forks too.

 

[Matt o]

Thank you for your input amc49. Does anyone else have any advice regarding the shift spring and whether it’s possible it’s causing me so many issues?

 

[amc49]

Not sure what you are looking for as I gave you everything you needed. FYI, I rebuild bike transmissions blindfolded. Along with car manual and automatics too.

Maybe I should explain. By detent I mean mainly the spring, it is 80% of the detent force that holds shifting in place and at same time enabling it to occur seamlessly. There is likely more than one there, NOT the big one the shifter shaft goes through, rather the smaller one that holds the detent cam follower into the shift drum notches. You can check the bigger one, simply move the shifter lever up and down to the extreme, the spring is what pulls the lever back to the middle, if bad the lever would simply flop up and down. The smaller spring is what locks the shift in, the solid feel and click as a normal trans goes into each gear.

 

[amc49]

https://www.partzilla.com/catalog/yamaha/motorcycle/1981/xs400-xs400h/shift-shaft-pedal

#2 which actually aids picking shift pins. Not #9 which is the bigger one I spoke of.

https://www.partzilla.com/catalog/yamaha/motorcycle/1981/xs400-xs400h/shift-cam-fork

#28 spring figures in there pretty big too, it actually provides detent force on the shift cam.

 

[Matt o]

Not sure what you are looking for as I gave you everything you needed. FYI, I rebuild bike transmissions blindfolded. Along with car manual and automatics too.

Maybe I should explain. By detent I mean mainly the spring, it is 80% of the detent force that holds shifting in place and at same time enabling it to occur seamlessly. There is likely more than one there, NOT the big one the shifter shaft goes through, rather the smaller one that holds the detent cam follower into the shift drum notches. You can check the bigger one, simply move the shifter lever up and down to the extreme, the spring is what pulls the lever back to the middle, if bad the lever would simply flop up and down. The smaller spring is what locks the shift in, the solid feel and click as a normal trans goes into each gear.

This is very helpful, thank you. I think the term detent is what was throwing me off. Thanks for clearing that up. I know what to look for now and I’m fairly sure that the smaller spring will be the issue in this case after having a look last night. I’m not sure if I can get hold of one here in the uk but I will have a good hunt.

thanks again,

Matt