How A Motorcycle Transmission Works 

You get two lots of drag. What he showed is just from friction between gears and shafts. It's why when you lift up your rear end with the engine on, the wheel might start to spin. You also get drag in the clutch. Sometimes the plates are making light contact, and sometimes it's just viscous coupling through the oil. Either way, it results in your input shaft spinning in neutral, even with the clutch fully in. Then when you click it into first, that entire input shaft assembly comes to a sudden stop as the dogs crash together. The angular momentum ("angular" because spinny thing) has to go somewhere, and that somewhere usually ends up being the rest of the bike being lurched forwards. I believe this to be either intentionally engineered into the system, or at very least, intentionally not engineered out of it (except on really small engines, where such clutch drag would sap too much power, such as on many 125s). This is because the gearbox *needs* the shafts spinning at different rates in order to ensure the dogs can slide past each other. If both shafts were static, unless they'd stopped in perfect alignment, the dogs would crash into each other when you attempt to get into 1st, and you'd bend the shift fork before you get it into gear if you try to force it.

Thanks Matt!

I'm working on a rebuild video for this engine. Both top and bottom end.

LOL now this video will be in your head every time you shift.

Thank you!

ok I have got one interesting video 2 minutes real view of how motorcycle transmission works ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-1i0pUk6xqCY.html this is what I wanted to see. Commenting if some one else comes here they can see both the video for better understanding.

Yes they tend to drip and this collects it all.

#1 tip, bench shift it before further assembly.

Chipped or worn teeth/dogs. Bent shift forks. Bent shift shaft.

Pretty much the same for all motorcycles. Same principles.

Yes

Clutch not installed in this video.

the clutch disconnects the engine from the gearbox, allowing the gearbox to operate without any load, which makes it easier to shift gears. The dogs are engaged or disengaged by the forks controlled by the shifter

Because motorcycles have a constant mesh trans. Car gears are not meshed and need to synch up so they don't grind.

@@HTMR Thx a lot for the reply! So as I take it, every shifting gear on the input shaft is constantly meshed to a free wheeling gear on the output shaft and vice versa, ok.. But every shifting gear engages with a wheeling gear right next to it on the same shaft, which is not meshed to it and therefore can have a different speed... as is the case when e.g. you shift from neutral into first gear, because in neutral the shifting sprocket for the first gear is not moving at all but when you shift into first gear its moving and transmitting power because it is locket with its wheeling gear ... and I feel when they meet they should be matched somehow which obviously is not the case because it works very well... thats what I mean.. I dont want to get on your nerves though (:

@@Ben7Seven 6:55 The actual parts that engages each other are dogs and slots. They are not delicate mechanisms like the gear teeth…only 4-5 dogs in a whole circle, with big blanks. They are quite tough because of their simple shapes, so they will withstand wear and collision during normal shifting, if not put in high pressure. There is no guarantee that, when you shift, the slot is exactly positioned for the dog part. I think there is about 30-40% chance that the slot is initially blocked. But since all those parts are spinning, the discrepancy will be resolved in a blink. Actually, this is the primary reason that we shouldn’t be stopping at high gear. It often get stuck at false neutral when we stop in 4~6 gear and then try to shift down to the first. It’s that 30-40% chance of dogs not fitting the slots!

@@gksalf10 Thx a lot for your clarification! makes sense..

in a car transmission, the dogs are much smaller and thinner and close together, so they can't mesh while spinning without the synchros. In a motorcycle tranny the dogs are wide apart and are able to mesh directly. This makes it possible to shift without the clutch, but is more noisy than a car tranny.

the clutch lets you put it in first from a stand still

@@truckertwotimes7189 Yes, but how. If the dogs aren't aligned when you engage the clutch, how does it let you get into first? (Not a rhetorical question by the way).

Shift forks bend usually when the shifter is forced. The clunking you heard is the dogs engaging on the gears as they meshed.

It *would* do damage but nothing serious for a now and then mistake, though it’s a habit you should break and try practicing getting the shifts consistent and enough but not too much pressure 👍

@@raphy_tt Alright, will take note from now on, and work on it. Thanks

Motion pro...I forgot the pn. I'll double check.

Here is the link amzn.to/35HKb6U

I'd start by taking the RH cover off and taking a look at the shift detent mechanism.

@@HTMR I had it down to the shift drum key/shift detent mechanism. it was stuck in 2nd. I took the washer off then worked it back and forth with a hammer and prybar... ouch! Bam it came free after about 15 mins of prying and bangin. lets hope it didnt mess anything up! ITs shifting now! I should have took a video. Thanks Man!

Yes, they wear over time. I would say violent shifts would be the worse on the dogs. Quickshifters/clutchless shifting can be just fine if performed correctly.

@@HTMR Thanks. I've just finished watching The Workshop video on quickshifters. What you said checks out & also I found out apparently low engine speed shifts is not good for quickshifters.

ബ്രോ ഇന്നത്തെ വീഡിയോ പൊളിച്ചു സൂപ്പർ 👍👍👌

I don't know of any motorcycles that have synchros.

that's what i've been looking for, i think it would be possible to change the 4th gear on my 07 Honda Shadow VT600CDA and give it an even bigger gap between 3rd and 4th to allow for less rpm's at 80 mph 🤔 what do you think?

Year make model?

@@HTMRlexmoto isca 2020

@@taylorpreston8502 I don't know that model at all. Pull the RH clutch cover off and see what the mechanism is doing.

Motorcycles do not have snychronizers. I have ridden a few triumphs and the transmission are never as smooth as other makes. Is the clutch in good shape?

@@HTMR it’s a new motorcycle just a month old, clutch is fine, just there is bang in shift from 1st to 2nd to 3rd and I been told triumph makes bike like this and it’s the bikes character :( why can’t it be smooth is my question to the Triumph

No, with overdrive the input gear is larger than the gear translating to the output gear, therefore making the output spin faster than input. If that makes sense. Anybody please correct me if I'm wrong.

Don't worry if you don't understand it though, I'm still having a hard time grasping some of it.

74 cb750

Nope, just let off the throttle and shift up. I do it all the time.

Obvious

@@oscarm9473 what do youean obvious?😅

Obvious the transmission is damaged

@@oscarm9473 should I replace it with new transmission? I didn't mind to have a check it up on the motorcycle dealers, since my MC runs in good condition so far.

By all means, grab a camera and try and do a better job and post it for me to comment on.

Thanks!