1. Dismiss Notice
  2. Hey Facebook people... We've created a group for XS400.com members to connect. Check it out!
    Dismiss Notice
  3. Want an XS400.com t-shirt? Go to the store to order. Limited sizes and quantities available.
    Dismiss Notice

RD400 whats wrong With my transmission ?

Discussion in 'The Garage' started by Salman_z8, Aug 18, 2020.

  1. Salman_z8

    Salman_z8 XS400 Member

    8
    0
    1
    Canada
    Hello all

    New guy here.
    i have been trying to post this on aircooled club, but something is up with their registration process i think.
    Since rd400’s shifting linkage is very similar to xs400, i am hoping someone can help me out.

    I’d appreciate the help.
     
  2. Salman_z8

    Salman_z8 XS400 Member

    8
    0
    1
    Canada
    Its a 77 RD400, unknown history, 10k miles, pretty decent shape and all there.
    Engines never been apart etc

    I mostly work on 4 strokes, i have worked on xs400.
    Carb service, tune etc
    I have rebuilt over a dozen motors and all running strong, ( i still have the bikes and ride them )
    Early cb750’s, cbx1000, kawi h1, z1, so that sometimes makes me think as if i know what i am doing ... i guess not lol

    Heres the kicker, the bike wont shift, not up nor down. No engagement feel of any sort.
    So with a heavy heart i took the clutch side apart.
    It seems as if the pawls dont make contact with the drum pins. What gives ?
    Now, if i rotate the drum to second gear by hand, and engage the pawls, i can go to all the way to 6th, and back to 2 nd no problem. But when it goes to neutral, just gets stuck there.
    I can shift to first by rotating the drum directly.
    I like to believe that this has something to do with the linkage and not bent forks.
    Any known issues with the torsion spring holding the claws ? Is it supposed to be tight or all loosy goosy.
    If someone happens to have their clutch side open, could they be so kind to post a video of the shifting action, so i can cross reference.

    sorry for the long, unXS400 post.
    If its a issue, and i overstepped, i apologize.
     

    Attached Files:

  3. amc49

    amc49 XS400 Addict

    You cannot shift ANY motorcycle trans completely through all gears without the trans input shaft turning, it is what allows the gear dogs on sides to line up whereupon the gears then move into full engagement. Don't spin the shaft and you are intentionally bending the shift forks as it is impossible for the shift to complete until those side dogs line up. One shift or another will complete if the dogs line up just by luck but not nearly all shifts will work.

    'It seems as if the pawls dont make contact with the drum pins.'

    Well of course they don't; the shift drum is half out of time as it cannot go all the way into full gear engagement. Where you end up with the fork pinning gear to one side because the dogs don't line up. You don't get any feel from that condition at all. Thinking you can go from 1 to 6 without rotating any shaft should be impossible. You are saying all 6 sets of dogs are lined up to do so, somebody would have to split the cases to line up each gear by hand to do that.

    I rebuild manual transmissions blindfolded, I used to set up Doug Nash full race 5 speeds for 10,000 rpm SBC and I rebuild automatics too.

    I sense some BS here, I could be wrong but I can't see anybody working on a CBX with thinking like that. I note the other trick bikes mentioned too, a wish list if you ask me, the experience level posted here is clear enough.

    I haven't done Honda SOHC (I have a CB550F but it refuses to break) or Z1 yet but they are just more engines to me as I have done hundreds of both car and bike, I raced Kaw 3s and Honda DOHC 4s. Plenty of 2 stroke but some earlier than RD, say YDS3-6B and YM1-2 250-305 and a bunch of them. That shifter was the shifter from hell as compared to RD stuff. Later full honk 10,000 rpm S3 400 Kaw triples I ported, restoring an H2C 750 right now.

    If I'm wrong about you then I apologize but you still have to prove it to me yet.

    Start turning the input shaft the clutch attaches to and THEN shift trans while doing it, the faster you turn it the better it works. The trans should be able to shift through everything with little trouble. You have to do that on bike trans as there are no true synchronizer rings in them like cars have. The side dog on the gear is the braking method there.
     
    Last edited: Aug 18, 2020
  4. amc49

    amc49 XS400 Addict

    Uh, if the shifter lever does not spring back to center from either direction high or low there is a spring broken, that will stop all shifting. There are generally more smaller springs on the claw(s) on shifter arm too.

    Pic yours with a phone to refresh my memory. Clutch assembly removed.
     
    Last edited: Aug 18, 2020
  5. Salman_z8

    Salman_z8 XS400 Member

    8
    0
    1
    Canada
    Hi thanks for the reply, i appreciate it.
    May be i didnt give complete information, i apologize.
    I do indeed know that motorcycle trannys do not have synchro gears, and shafts need to be turning to engage shifts. The output and primary shafts are turned by hand while shifting, and it does indeed shift fine.
    That is why i believe that the forks might be fine.
    The detent plunger is in place and not broken, the cam detents seem to be in the right spot.

    But the shifting pawls run out of movement before being able to rotate the drum, if starting from neutral. Thats why i was curious about the pawls torsion spring.

    i do indeed have those bikes and work on them, no i am not offended at all. Honestly if this was a cb tranny or kawi tranny, ( which i always undercut anyways, and inspect forks since engine is a full rebuild ) but i do not want to tear anything down.

    i appreciate the reply, but trust me i have tested with all the things you are saying and then having the trouble i am.
     
  6. Salman_z8

    Salman_z8 XS400 Member

    8
    0
    1
    Canada
    To be more specific;

    Gear meshing is not the issue, but being able to rotate the shift drum is the problem. The pawls just dont contact the pins right. Once they do, it shifts fine.
    Which is why this issue is baffling me a little, and i dont know enough about yammy trannys, to know if there was a known cause for this.
     
  7. amc49

    amc49 XS400 Addict

    Please forgive me for earlier being the dick I often am.

    The link to shifter parts..............the roller #5 must be there, iif broken and fallen away you would only get partial movement of the drum.(pins).

    Both #3 and #9 are springs and all of the spring has to be there.

    New link and the rest of the shifter.......

    https://www.yamahapartshouse.com/oemparts/a/yam/5004182af8700209bc784ed9/shift-cam-fork

    Look at part #9 in that one and recognize the shifter cam part which is usually right next to the pins in other designs, on that one they put it on the OPPOSITE end of the main shift drum. Most designs have the shift drum use a double row for the pins, one groove in a row is for the shifter to grab and pull the pins and the other is for the shifter cam detents which use the longer pins in that design to lock the cam down into shifter travel 'segments' corresponding to each gear position.

    NO shifter pulls 100% on the pin to positively pull the shifter drum ALL the way into gear, they rely on that shifter cam to pop the gear the last 10-15% or so into gear. Meaning when you get down and look close the shifter linkage will never pull the pin ALL the way to the next location, only part way. When it gets that close the shifter cam is what loads the drum enough to rock it over the last amount to fully pop into gear. If you don't get that final snap or rock into gear then likely the shifter cam spring has broken or fouled in some way, that spring is what pops the cam into its notches.

    There is a 3 bolt small cover on the other end of that shifting drum, it might behoove you to remove it if it is behind the main drive sprocket cover, which it almost has to be. Don't know if it is internal or external but spring #29 has to be good or problems with the cam not popping the drum the rest of the way over. Removing that cover will at least allow you to view the last bit of pop-over action the cam imparts to the partial shifter drum movement to complete the shift. Or not, if the movement is flawed due to some error.

    On most other trans that 'snapping the rest of the way' action is viewable by watching where you are now, not on this design. Yamaha broke the shifting into two pieces as far as viewing it. You just have to know that the rollover complete the shift action must still occur, the shifts will not happen and flying out of gear will show up with no detents to hold the drum in a solid position.
     
    Last edited: Aug 18, 2020
  8. Salman_z8

    Salman_z8 XS400 Member

    8
    0
    1
    Canada
    Thank for the detailed reply.
    I am not offended in any way at all, and do i appreciate the detailed reply and your time.

    i have the sprocket side off already, its covered in crud and soaking. I will clean and take that cover off as well and inspect.

    my understanding is that the shifter cam does fall into its detents. ( not with the shift only ofcourse, but after i turn the primary shaft )
    What baffles me is that somehow when the drum rotates back to neutral ( 6-5-4-3-2- n ) it loses grip/ reach on the drum pins. which is very odd.

    None the less, i will look at the other side and physically check the engagement of the shift cam

    at one point i had though that maybe the claw torsion spring is not putting enough tension. But its just odd. I am pretty hopeful that forks are not bent.

    adjustment of the claws alone doesnt seem to be getting me out of it. I did pull out the plunger to inspect and looked good.

    I will try to make you a video and see if that makes some sense to you, it sure is giving me a hard time.

    but once again, i am grateful for your time

    salman
     
  9. amc49

    amc49 XS400 Addict

    If the 'claws' are coming off then they are likely worn. Never seen it before but that means nothing. The spring only keeps them in place to be hooked already or down enough to be, it does NOT provide the full force of holding them in place and not supposed too. It just keeps them located right there only.

    '...the shifter cam does fall into its detents.' Not fall, I would characterize it as stronger than that, most snap into place very firmly and seek to the low spot instantly. How they complete a shift only 85% done. Bear in mind the main roller bearing that holds end of drum on the right, bearing dragging could hold that back. The end behind sprocket appears to be like most and simply sets in case aluminum.
     
  10. amc49

    amc49 XS400 Addict

    Second pic part #13 and the neutral locator, that pin and spring must be good too along with main pin that locks the cam in place.
     
  11. amc49

    amc49 XS400 Addict

    First pic...................part #10 and thinking #6?, the one between the main big spring ends. One of those points is eccentric and adjustable and you adjust the shifter arm with claws using it to grab equally going in both directions, upshift and down. IIRC and a long time ago you adjusted it to equal distance between the spring ends or something similar, it affects the claws grabbing both ways, making it equal or one way gets more bite than the other. Obviously you don't want the latter-that claw will then miss hooking or not rotate far enough to let cam throw drum the rest of the way over.

    (edit) Oops, I see you already found that adjustment.........

    'None the less, i will look at the other side and physically check the engagement of the shift cam

    at one point i had though that maybe the claw torsion spring is not putting enough tension. But its just odd. I am pretty hopeful that forks are not bent.'

    You must consider the cam before you can go there, if it is locking into each notch hard or trying to then likely a fork is bent to drag on the drum to not complete full movements.
     
  12. Salman_z8

    Salman_z8 XS400 Member

    8
    0
    1
    Canada
    Hey there. Was caught up with a few work things for the past week or so.
    Made some progress.
    I feel like since there was a Significant amount of sludge in the motor, and not having moved in a decade, things were sticky and seem less sticky now. removing the detent plunger probably helped along those lines as well.
    It doesnt shift perfect, but shifts.
    I am very hopeful that once the motor runs, the shafts spinning faster will aid with that. Few short mileage oil changes should clean the rest up.

    i am pretty sure i was the first one to remove the clutch cover, nothing seems to be missing.
    Rd400’s, do have a backing plate on the shift drum pins, so adjustment gets a little tricky to be perfect.

    Does this have to be a 100% even ? Or almost perfect is good enough ?

    i saw a slight crack on the neutral switch cover over the drum, and chose to not disturb it for now till either i have a different one or it starts leaking.

    waiting for gaskets, and a carb needle to button this up. Putting in electronic pickups in place of points, as the points were falling apart.

    should be able to try it to run in a week or so. Will know more than.
     
  13. amc49

    amc49 XS400 Addict

    Shifting while spinning the input by hand is always jerky, it works much better with the shafts spinning faster.

    Luck.............
     
  14. Salman_z8

    Salman_z8 XS400 Member

    8
    0
    1
    Canada
    I agree. But it was shifting fine once in position, just would not engage the drum pins. my guess is the cam neeeds some help from the vibrations and new oil, to self align.

    Will keep you posted once its running
     
  15. Salman_z8

    Salman_z8 XS400 Member

    8
    0
    1
    Canada
    Hey
    So finally have the motor running.
    I guess the crank seals will show themselves if they feel like it, but it is running. And shifting.
    The little bit of adjustment, and cleaning has sure helped.
    I really appreciate your time, as i am quite unfamiliar with these particular bikes, i wanted to make sure my work gets double checked.
    Hate taking a gasket off, second time around.

    Have some piston slap on one side, but i will ride it when i can. Then maybe go over size, if i still have it, and do the seals too.

    Appreciate your help.
    Let me know if there is anyway i can ever help you.

    salman
     
  16. amc49

    amc49 XS400 Addict

    Most 2 strokes fail from bottom rod big end bearing failure if they don't break skirt from slapping too much. RDs have strong skirts because of the reed induction holes. The rod bearings fail because the oil supply is cut by gas and why the skirts wear so fast too. The common 2 stroke gets maybe half the life mileage a 4 stroke does due to that lack of really good lubing. I had trouble getting 20-25K miles out of any one of a long stream of them but I hotrodded them at times.

    If running ethanol in the fuel that will be even shorter, ethanol stops the oil from binding closely to the metal, needed to lube it correctly. 2 stroke crank bearings hate that stuff.
     

Share This Page