N-1-2 shifting problems

Discussion in 'Tech Area' started by Tripod, Aug 3, 2018.

  1. Tripod

    Tripod Member

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    Hi guys, got a question about a transmission shifting problem im having. I recently rebuilt an engine that ran, but with low compression. It shifted fine before the rebuild, up, down, pre-load was perfect.

    I rebuilt it with all new honda parts, however, a few parts that went back in on the rebuild were the shift drum, shift shaft, and gearshift arm. Shift drum measured in spec. During reassembly, it went through all the gears as best it could without the assistance of the mainshaft/countershaft moving. I know it likes to have everything lubricated and moving for optimal shifting. I put blue loctite on the shift star.

    I reused the shift drum, and replaced the shift forks with OEM. I used 24221-041-010 for the right shift fork, still available from Partzilla. The left fork is NLA, but DrAtv advertises http://dratv.com/lshalctal.html as a fork that works, according to DG.

    It seems like it is binding up on the drum and not allowing it to upshift through all the gears. Its a struggle to go from 2-1, which I assume is moving over inside the transmission from the left fork to the right fork.

    I'd appreciate any insight that you could offer. Oh, and it runs great! Thanks for all the information posted through the years.
     
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  3. kirrbby

    kirrbby Well-Known Member

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    Did you adjust the auto clutch after you put it all back together? Did you point the clutch lifter... arm straight at the center of the clutch? Did you make sure the small primary gear was properly indexed into the back of the clutch?
     
  4. racerx

    racerx Administrator
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    Have you checked case-to-shift fork clearance, and endplay of the shift drum assembly, with the case halves torqued (as they are now)?

    First thing I'd want to do is check for binding. Pull the plastic plug that covers the shift drum fixing bolt. Then, using a socket, shift through the gears...in both directions. If the drum rotates freely, in both directions, then the issue is upstream of the tranny - most likely the clutch release linkage is incorrectly indexed - i.e off by one spline. OTOH, if binding is felt while shifting via the drum fixing bolt, time to pull the clutch cover and inspect the shift linkage & detent assembly. There's even a chance that the cases will have to be split. That said, before taking action that drastic, check the easier stuff (which is everything else) first. Odds of finding & being able to correct the problem w/o splitting the cases is high.
     
  5. Tripod

    Tripod Member

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    I adjusted the preload on the clutch. The arm is pointed straight at clutch. Yes, the small primary gear is facing the right way and indexed into clutch.

    I havent checked case to shift fork clearance. Im not sure how I would do that.
    During assembly, there seemed like more endplay on the drum than I would like. The bore diameter in the case half where the drum rolls also seemed to be more than I would expect, yet the drum o.d. measured in spec. Also the right fork seemed to cock left & right when sliding sideways on the drum.

    There is definately binding when indexing through the gears using the drum index bolt. Again, its mostly between 1st and 2nd gear.

    What is the part number for the drum that is available if I need to go that route? Is there a secret menu of superceded parts that are NLA that work on z50's? I.E. how far up through the years can I dig for interchangeable parts?

    Im definately scratching my head on this. My better judgement said to find it before putting the motor together, you know, the voice in the back of my mind. OTOH, "it doesnt like to bench shift" was also kicking around too.
     
  6. allenp42

    allenp42 Active Member

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    Used shift drums are cheap and all over e-Bay and here as well. Personally, I've never run across a bad one....but I don't have as much experience as others on this site.

    Regarding the shift drums, I don't see that the left shift drum is NLA on Partzilla. This is news to me. NEVH has them as well. The p/n is 24211-087-010

    "OTOH, if binding is felt while shifting via the drum fixing bolt, time to pull the clutch cover and inspect the shift linkage & detent assembly."
    Yep, I've experience this once. Can't remember exactly what I did wrong but is was obvious once I pulled the cover and poked around a bit.
     
  7. Tripod

    Tripod Member

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    I didnt see anything visually wrong with the drum during inspection. You are correct that 24211-087-010 IS available. Unfortunately, Partzilla doesnt list superceded parts very well.
     
  8. racerx

    racerx Administrator
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    The most recent one, late last year, that had the dreaded case-to-fork contact. You're right, it wasn't easy to locate much less figure out. What I noticed is that the tranny would bench shift just fine, until the case screws were tightened.
     
  9. Tripod

    Tripod Member

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    I checked all the easy stuff but no luck.
    The motor is currently torn down. Drum OD measures in spec. No signs of rubbing, chipped teeth, or missing thrust washers.
    The old shift forks measured still within spec, but I replaced them as I didnt want to have to tear down the motor anytime soon. So much for that.

    I see the left fork binding a bit on the countershaft when shifting through the gears. The right fork seems to want to bind a bit at a certain spot on the drum. Nothing visually is glaring to my untrained eye. I have tried rolling through the gears with both new forks, one old fork and one new fork, and both old forks. For whatever reason, it works best with old forks. That's probably how I will leave it.
     
  10. racerx

    racerx Administrator
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    I cannot envision how this would even be possible. A little more information could be very helpful.

    FWIW, I've rebuilt a lot of 3-speeds, using the newer-type shift forks...which have been around for decades now...and they've always shifted as you'd expect with a Honda, except for the couple of oddballs where case interference/contact occurred. Something here isn't making any sense...yet.

    I'd suggest placing a couple of layers of masking tape in the shift fork bodies, where they come closest to the cases to make the detective work easier. Then partially reassemble the lower end, just what it needed to shift through the gears, plus enough case screws to hold the case halves together, with the screws torqued.

    FYI, the early type 3-speed shift forks are only available as NOS and getting harder to find. Frankly, they weren't durable which is why Honda changed the design, relocating & enlarging the contact pads.
     

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