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Thread: 1974 R90/6 refurb

  1. #31
    God? What god? roborider's Avatar
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    I got the re-sleeved master cylinder back from Apple Hydraulics in New York today. They did a fine job. You can see the nicely fitted and honed brass?? sleeve they inserted. I got it all back together and the front brake works quite well now. I'm quite happy with the braking for the first time since I bought the bike.

    All I have left now is to install the new points, set the timing, check the carb balance one last time, and she's ready to go. I'll still work on the seat and lubricate the center stand and some other things here and there, but she'll be pretty much ready to ride on Saturday.

    I'll give it a good wash and take some final pictures, then it's time to put on some miles.

    Oh, yeah, maybe I'll get a license plate....

    Here's the re-sleeved master cylinder. It was $90 to have this done.
    Rob C. , Raleigh, NC
    '10 R12RT, R90/6
    2007 CBR600RR & 09 V-Star
    Suzuki DR 350

  2. #32
    God? What god? roborider's Avatar
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    It's done! Took it out for a ride today and it runs well. The down shift from 3d to 2d is a bit tough, but unless it becomes more serious, it's fine. It fires up perfectly from dead cold and has good strong power. It got a wash today and joined the seraglio. I'll get a plate tomorrow and get some good miles on it next week.



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    All four of the sisters:
    Rob C. , Raleigh, NC
    '10 R12RT, R90/6
    2007 CBR600RR & 09 V-Star
    Suzuki DR 350

  3. #33
    God? What god? roborider's Avatar
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    I've been riding the bike but the issue with shifting from 3d to 2d is just too annoying. I removed the trans to have a look. Here's a shot of the transmission. You can see the gears look great. I'd like to do the rebuild myself, all the information and special tools are available, but I decided to send it out. At this point, wanting to ride wins out over wanting to wrench. Plus, I figure I'll get back a tranny that will last as long as I do and I will be done with it.

    The only thing 'wrong' I could find was that NONE of the three shafts had end play shims. That can't be right!

    Last edited by RoboRider; 04-05-2012 at 10:51 PM.
    Rob C. , Raleigh, NC
    '10 R12RT, R90/6
    2007 CBR600RR & 09 V-Star
    Suzuki DR 350

  4. #34
    God? What god? roborider's Avatar
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    I decided to rebuild this transmission myself. The special tools are available and I have this kind of knowledge and a well stocked shop with all of the common tools needed (and now many of the special tools). Transmissions are much simpler to rebuild than engines I will say.

    Firstly, I had a VERY NEGATIVE experience with Tom Cutter of Rubber Chicken Racing and I do not recommend you use him. Although I have no doubt that his workmanship is flawless, his business ethics and customer skills are horrible. I emailed him and asked for an estimate of turn around time before sending my transmission to him, and he replied "6 to 8 business days minimum." After a month, I emailed to ask how it was going. His reply was curt and rude, and so I had him return my transmission to me untouched. He was, to be blunt, a curmudgeon. I found out that a fellow MOA member sent him a trans in February and still does not have it back. I don't begrudge him being busy, but he just outright lied to me about how long it would take. If you choose to go with Tom, send him your work in the Fall so that you can use the Winter down time to your advantage, and don't expect any warm and courteous emails.

    The good news is that I decided to do it myself. I wanted to anyway, but I felt I didn't have the time and wanted to ride the bike. But, given the circumstances, I'm doing it.

    I bought the most excellent DVD from Cycle Works that goes through a transmission rebuild; this is a great video. Between that, the Clymer manual, and online resources (such as Snow Bum) I felt ready to dive in.

    The nice thing is that all the bearings, shift forks and gears, etc., look great. So I don't need expensive parts. Just new seals and gaskets. As I said earlier, there are no shims for shaft endplay in this transmission. Whoever did it last time skipped this important step. I ordered shims and will correct this problem.

    But here's what I found. To refresh your memory, the transmission was getting stuck in 3d gear when down shifting to 2d gear. I had to keep hitting the shift lever repeatedly to get it go shift, applying a lot of force. This problem was reproducible on the bench.

    What I found was that the shift cam slot was too tight, and was binding on the shift fork (just for one fork). I'll show some pictures. The one shift cam was fine, and the forks would glide effortlessly in the slots. The other shift fork and cam were bad. The fork was completely getting bound up. It was as if the cam had shrunk, but yet it looked perfectly fine and straight so I don't get it.

    I used my Dremel tool to grind the slots where they were binding and got enough freeplay so the fork slides well. I put it back together and it shifts perfectly now. So once I get the new seals and gaskets, etc., I'll put it back together and I'm good to go. If I ever have a transmission problem, I know this thing inside and out now and have no fear of failure in the future.

    Pics to follow.
    Rob C. , Raleigh, NC
    '10 R12RT, R90/6
    2007 CBR600RR & 09 V-Star
    Suzuki DR 350

  5. #35
    God? What god? roborider's Avatar
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    Here's some pics.

    This is the shift cassette. You can see the two cams with the curved slot races that the shift fork ball goes in. As the cam turns, it lifts and lowers the shift fork (and hence the dog gear). The fork on the left was binding badly in the slot, it was not wide enough, and I widened it with the Dremel until the fork ball traveled smoothly from end to end.

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    Next it was time to drop the shafts back in the case. The case needs to be hot (above 200 F) to expand the bosses to receive the bearings. You can see the bearing on the bottom of the shaft, and the corresponding hole or boss where it drops into the case. I set the case on the kerosine heater for 5 minutes to heat it and the shafts went right in. Let me tell you, it's hot here today and running the kerosine heater was no fun.

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    Here's the shafts and one shift fork (the problem one) in the case. Once the case cools, the bearings are locked in place.

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    And finally, the shift cassette in place. You can kind of see how the shift fork rides in the slot of the cam. It no longer is binding and shifting really well on the bench now for the first time.
    Rob C. , Raleigh, NC
    '10 R12RT, R90/6
    2007 CBR600RR & 09 V-Star
    Suzuki DR 350

  6. #36
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    B.P., MN
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    Thanx much for the great pics, my '74900 when under hard throttle will sometimes miss third going up. In future I definitely will consider prying it open myself.

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